XXXIV Meeting of Astronomical Society of India Kashmir University, Srinagar 10-13 May 2016

ABSTRACT BOOK- ASI 2016 Table of Contents

Sl. No Title Page No. 1. Vainu Bappu Talk- Nikku Madhusudhan - Chemical Characterization of Extrasolar 1 Planets 2. Sukanta Bose - Special Lecture on GW Detection 1 i. 3. Parallel Session – Instrumentations and Techniques - I 2 4. Shiang-Yu Wang - Optical/IR Instrumentation Projects in Taiwan 2 5. Raghavendra Prasad B - Effect of source profile and wavelength on scatter distribution 2 over the field of view of Visible Emission Line Coronagraph on board ADITYA-L1 Mission 6. K. Sankarasubramanian- Novel Solar Spectro-polarimetric concepts for Future 3 Telescopes 7. Arun Kumar Naidu - PONDER - A Real time software backend for pulsar and IPS 3 observations at the Ooty Radio Telescope 8. Saurabh Singh - On the Detection of Global 21-cm signal from Reionization using 4 Interferometers i. 9. Parallel Session - Stars, The Milky Way Galaxy and its Neighbours - I 5 10. Tapas Baug - Galactic bubble N37 and surrounding star formation activity 5 11. Lokesh Kumar Dewangan - A multi-scale, multi-wavelength study of massive 6 star-forming region W42 12. Jessy Jose - Effect of stellar feedback on subsequent star formation activity 6 13. Kaushar Vaidya - Optical Spectroscopy of X-ray Selected Young Stars in the 7 Carina Nebula 14. Aruna Goswami - Carbon-Enhanced Metal-Poor stars: evolution, 7 nucleosynthesis, observations and the impact on cosmochemistry 15. Susmitha Rani Antony - Oxygen abundances in carbon enhance metal poor (CEMP) 8 stars: Comparison between CO and [OI] lines i. 16. Parallel Session - Extragalactic Astronomy - I 9 17. Soumavo Ghosh - Effect of Dark Matter halo on spiral structures of different scales 9 18. Suvendu Rakshit - First spatially resolved black hole mass of quasar 3C273 9 19. Kartick C Sarkar- Multi-wavelentgh emission from galactic winds and Fermi Bubbles 10 20. Vikas Chand - Spectral Study of Gamma Ray Bursts ssing Czti of ASTROSAT 10 21. Indranil Chattopadhyay - Simulation of accretion disc and multiple shocks 11 22. Rupak Roy - Luminous Supernovae : Implication of shock interaction on the observed 11 properties i. 23. Plenary Session: ASTROSAT-First Science Results 12 24. S. N. Tandon - Calibrations of UVIT and the first scientific results 12 25. K. P. Singh - First Scientific Results from observations with the Soft X-ray 12 imaging Telescope onboard ASTROSAT 26. M. C. Ramadevi - SSM on ASTROSAT: First Results 13 27. J. S. Yadav - Large Area X-ray Proportional Counter (LAXPC) instrument 13 Table of Contents

onboard ASTROSAT 28. S. Vadawale - Initial results from Astrosat CZTI 13 i. 29. Parallel Session - Extragalactic Astronomy – II 14 30. Lijo Thomas George - Low Frequency Study of Merging Galaxy Clusters using the 14 MWA 31. Deovrat Prasad - Role of cooling and AGN jets in the evolution of cool-core galaxy 15 clusters 32. Pradeep Chandra - VHE gamma-ray observations of Markarian 421 and B20806+35 15 using TACTIC during 2015-16 33. Rubinur Khatun - Radio Observations of Candidate Dual Active Galactic Nuclei in 16 Double Peaked Emission Line Galaxies Zahiri. 3 Ahmad Shah - Multi-Wavelength Study of 3C454 During August 2015 Flaring 16 ii. 34. Parallel Session - Sun and Solar System - I 17 35. K. Chenna Reddy - Strengths and limitations of the Gadanki MST radar for meteor 17 observation 36. Gurpreet Kaur - Modelling the thermal evolution and differentiation of interior of Mars 18 and Mercury 37. Ayesha Maryam Mazarbhuiya - Imaging polarimetric study on Comet 32P/Comas- 19 Sola 38. Rohit - Characterisation of non-thermal solar emissions at low radio frequencies 20 39. Kumar Venkataramani- Study of Molecular Gas Emissions from Cometary Coma 20 40. Avyarthana Ghosh - Fan Loops Observed by IRIS, EIS and AIA 21 i. 41. Parallel Session - General Relativity and Cosmology - I 22 42. Abhirup Ghosh - Testing general relativity using golden black-hole binaries 22 43. Nisha Rani - Parametric and nonparametric contraints on Transition redshift 23 44. Archisman Ghosh - Prospects of estimating cosmological parameters from 23 gravitational-wave observations of coalescing binary black holes 45. Shankaranarayanan S - Low scale Higgs Inflation with Gauss Bonnet Coupling 24 i. 46. Parallel Session - Stars, The Milky Way Galaxy and its Neighbours - II 25 47. Lalitha Sairam - Magnetic activities in the outer atmospheres of RS CVn-type Binaries 25 48. Arti Joshi - Photometry and Polarimetry study of Cataclysmic Variables (CVs) 25 49. Anindita Mondal- Abundance analysis of the Recurrent nova RS Ophiuchi (2006 26 outburst) 50. Mayukh Pahari - Spectro-temporal analysis of X-ray binaries using LAXPC on-board 26 ASTROSAT satellite 51. Gaurava K Jaisawal - Suzaku observations of the Be/X-ray binary pulsar GX 304-1 27 52. H. M. Lee - Dynamical Formation of Compact Binaries in Dense Star Clusters 27 i. 53. Plenary session: Dynamical systems 28 54. S. Sridhar: The disruption of multiplanet systems through resonance with a binary orbit 28 55. J. S. Bagla : Gravitational clustering in an expanding universe 28 56. Farooq Ahmed : Gravitational Clustering of Galaxies: Derivation of distribution 29 function using statistical mechanics of cosmology many-body problem Table of Contents

i. 57. Parallel Session - Extragalactic Astronomy - III 30 58. R. Srianand - On the star formation in high-z DLAs 30 59. J N H S Aditya - Cold Gas in High Redshift Galaxies 30 60. Charles Jose - Non-linear clustering of high redshift galaxies 31 61. Katherine Rawlins - Multi-component H2 absorption in a damped Lyman-α absorber at 32 zabs = 2.054 - spectroscopic analysis & simulation 62. Sonali Sachdeva - Evolution of disc galaxies for the past 8 Gyrs 33 Sandeepi. Rana - HI intensity mapping, co-adding and cross-correlation 33 ii. 63. Parallel Session - Instrumentation & Techniques - II 34 64. Maheswar Gopinathan - 3.6m Devasthal Optical Telescope (DOT): Commissioning and 34 early science 65. Sunetra Giridhar - HESP: an echelle spectrograph for 2m HCT 34 66. Prasanna Deshmukh - Simulator for Primary Mirror Control System of Segmented 35 Mirror Telescope 67. Vineeth Valsan - Development of Stressed Mirror Polishing Technology 35 i. 68. General Relativity and Cosmology - II 36 69. K. Subramanian - Origin of Cosmological magnetic fields: Primordial AND dynamos? 36 70. Shishir Sankhyayan - Large Scale Structures and Clusters-Voids Cross-correlation 36 71. Rajesh Mondal - Statistics of the epoch of reionization 21-cm signal : Power spectrum 37 error-covariance 72. Asif Iqbal Ahangar - Entropy excess and energy deposition profile in galaxy clusters up 37 to virial radius 73. Bidisha Bandyopadhyay - Can Annihilating Clumped Dark Matter lead to Helium 38 Reionization? i. 74. Parallel Session - Stars, The Milky Way Galaxy and its Neighbours – III 39 75. Sharanya Sur - Galaxy outflows without supernovae 39 76. Naveen Yadav - Dynamics of Supernova Driven Supershells 39 77. Jayant Murthy - Modeling the diffuse ultraviolet background 40 78. Smitha Subramanian - Signatures of a tidally stripped stellar population from the inner 40 regions of the Small Magellanic Cloud 79. Samir Mandal - Spectral properties of pair-plasma in disc-jet system around black hole 41 i. 80. Parallel Session - Sun and Solar System - II 42 81. Piyali Chatterjee - Mystery of repeatedly flaring delta sunspots 42 82. Sreejith Padinhatteeri - Delta-sunspot groups and Solar Flares 42 83. Suruchi Goel - The statistical study of global properties of sunspots in SoHO/MDI 43 continuum images over solar cycle 23 84. Vaibhav Pant - Kinematics of fast and slow CMEs 43 85. Tanmoy Samanta - Response of chromospheric jets in the corona 44 i. 86. Plenary session: Multi-messenger Astronomy 45 87. Varun Bhalerao: Einstein's messengers: Gravitational wave sources and their 45 electromagnetic counterparts Table of Contents

88. Amol Dighe: Pauli's messengers: Looking at the sky in neutrinos 45 89. Kuntal Mishra: Optical Transients 46 i. 90. Thesis Presenation 47 91. S. Rathna Kumar - Determination of $H_0$ through monitoring of gravitationally 47 lensed quasars 92. S. Athiray - Study of lunar surface chemistry using Swept Charge Devices 48 93. Samyaday Choudhury - Study of evolved stellar populations in the Magellanic Clouds 49 94. K. Sasikumar Raja - Radio Polarization Studies of the Solar Corona at Low - 50 frequencies 95. Drisya K - Studies on Carbon Enhanced Metal Poor (CEMP)stars 51 96. Raja Bayanna - Study of coupling between the layers of the solar atmosphere at high 52 resolution 97. Archana Soam - Investigation of galactic star forming regions and young stellar objects 53 98. V.Venkataraman - Infrared investigations of circumstellar matter 54 i. 99. Poster Presentations- Sun and Solar System 55 i. 100. Poster Presentations- Stars, The Milky Way Galaxy and its neighbours 67 ii. 101. Poster Presentations- General Relativity and Cosmology 96 iii. 102. Poster Presentations- Extragalactic Astronomy 108

103. Poster Presentations- Instrumentation and Techniques 135

ASI 2016 – Abstract Book 1

Tuesday, May 10, 2016

ASI2016_1001 Nikku Madhusudhan 11.30 am – 12.00 pm Vainu Bappu Talk

Chemical Characterization of Extrasolar Planets

Exoplanetary discoveries in the past two decades have unveiled an astonishing diversity in the physical characteristics of exoplanetary systems, including their orbital properties, masses, radii, equilibrium temperatures, and stellar hosts. Exoplanets known today range from gas-giants to nearly Earth-size planets, and some even in the habitable zones of their host stars. Recent advances in exoplanet observations and theoretical methods are now leading to unprecedented constraints on the physicochemical properties of exoplanetary atmospheres, interiors, and their formation conditions. I will discuss th1e latest developments and future prospects of this new era of exoplanetary characterization. In particular, I will present some of the latest constraints on atmospheric chemical compositions of exoplanets, made possible by state-of-the-art high- precision observations from space and ground, and their implications for atmospheric processes and formation conditions of exoplanets. The emerging framework for using atmospheric elemental abundance ratios for constraining the origins and migration pathways of giant exoplanets, e.g. hot Jupiters, will also be discussed. A survey of theoretical and observational directions in the field will be presented along with several open questions on the horizon.

Special Lecture on GW ASI2016_1021 Sukanta Bose 12.30 am – 1.00 pm Detection

Special Lecture on GW Detection

I will summarize the nature of the gravitational wave signal that was recently detected by LIGO. This is the first direct observation of gravitational waves. It was emitted by two colliding black holes 1.3 billion years ago. In addition to describing the physics of theobserved black hole system, I will discuss what might lie ahead for scientists aiming to use gravitational waves to push the frontiers of physics and astronomy.

ASI 2016 – Abstract Book 2

ASI-2016 Parallel Session - Tuesday, 10 May, 2016

Instrumentation and Techniques-I [Chairperson: Eswar Reddy]

Time: 16:00 - 17:30 Venue: Biotechnology Auditorium

ASI2016_1067 Shiang-Yu Wang 16:00 – 16:20 Invited

Optical/IR Instrumentation Projects in Taiwan

The astronomy development in Taiwan has a short history. 25 years ago, there was only around 5 astronomers on the island. However, the growth of astronomy was substantial and now there are more than 200 astronomers in Taiwan. The development was based on the strategy to develop both the science and instrumentation capabilities simultaneously. In the optical and infrared wavelength, we collaborate with world class telescopes for the development of large instruments while we also work on small robotic telescope system. In this talk, I will cover the current major projects including the SPIRou for CFHT, the Prime Focus Spectrograph (PFS) for Subaru telescope and the Transneptunian Automated Occultation Survey (TAOS II) project.

ASI2016_937 Raghavendra Prasad B 16:20-16:40 Oral

Venkata Suresh Narra, Indian Institute of Astrophysics. Raj Kumar N, Indian Institute of Astrophysics. Jagdev Singh, Indian Institute of Astrophysics Effect of source profile and wavelength on scatter distribution over the field of view of Visible Emission Line Coronagraph on board ADITYA-L1 Mission Visible Emission Line Coronagraph (VELC) on board ADITYA-L1 mission is an internally occulted mirror coronagraph designed for solar coronal studies over the field of view (FOV) ±1.05Ro-3Ro. (Ro - Solar Radii). VELC is designed for simultaneous study of solar corona using spectroscopic, spectro-polarimetric and imaging modes. To realise the proposed science goals of the payload, instrument background has to be minimal (<= 5ppm). Major contributor to the instrument background is the scatter due to roughness over the primary mirror (M1) surface. VELC being an internally occulted system, scatter light generated at the primary mirror surface due to all source points (angular size ±16arcmin) do not contribute equally to the scatter over FOV. Since VELC covers a wide band of wavelength ranging from 5000Å - 10747Å, scatter over the FOV at different wavelengths is not the same. In this paper, effects of extended source and wavelength on scatter distribution over the FOV of VELC are explained. Simulations are carried out using Advanced System Analysis Program (ASAP).

ASI 2016 – Abstract Book 3

ASI2016_694 K. Sankarasubramanian 16:40 – 17:00 Oral

Mohana Krishna (ISRO Satellite Centre), Raja Bayanna (Udaipur Solar Observatory), Shibu Mathew (Udaipur Solar Observatory), Ashoka, B. N. (ISRO Satellite Centre), Kumar (ISRO Satellite Centre), Maji (ISRO Satellite Centre)

Novel Solar Spectro-polarimetric concepts for Future Telescopes

The primary drivers of all the solar dynamics are the magnetic fields in the solar atmosphere and its interplay with the plasma. In order to quantitatively measure the magnetic field, spectro-polarimetry is an important tool. Hence, solar spectro-polarimetry plays a vital role for quantitative measurement. At present there are two different ways of carrying out the spectroscopy of the solar atmosphere: (i) a slit based spectrograph to obtain full spectra of the line of interest while scanning of the slit is used to cover the spatial direction, and (ii) narrow band imaging using Fabry-perot (FP) instruments to obtain 2D monochromatic image of a field-of-view and the line profiles are obtained by scanning the FP. Both the methodology has the difficulty of obtaining high cadence due to the scanning either in the spatial or in the spectral domain. This limits the time cadence which can be obtained in typical spectro-polarimetric mode of observations. With large aperture solar telescopes in the horizon (for e.g. DKIST, NLST, and EST), the next decade would be the high spatial resolution observation of the Sun. However, to make use of the higher spatial resolution capability of the telescope, the backend instruments also should have the capability to obtain high cadence observation to retain the spatial resolution. Hence, novel ideas in instrumentation are required to achieve this. In this paper, four novel techniques which are proposed to obtain high cadence observations will be discussed. Out of the four, our group has developed and demonstrated two of the techniques and its capabilities. A table of comparison of all the four techniques and preliminary results from the two techniques developed in our group will be discussed.

ASI2016_854 Arun Kumar Naidu 17:00 – 17:15 Oral

B.C Joshi P.K Manoharan M.A KrishnaKumar

PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope

I will discuss about a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time- stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a bandwidth of about four times larger (16 MHz) than that of the legacy system as well as its fluctuation spectrum with high temporal and frequency resolutions. The key point is that all the above modes operate in real time. I will present the design aspects of PONDER and demonstrate its usefulness for a variety of astrophysical studies using the high sensitivity of the ORT.

ASI 2016 – Abstract Book 4

ASI2016_610 Saurabh Singh 17:15 – 17:30 Oral

Ravi Subrahmanyan, N. Udaya Shankar, A. Raghunathan Affiliation: Raman Research Institute

On the Detection of Global 21-cm signal from Reionization using Interferometers

Epoch of Reionization (EoR) marks the transition of baryons in the Universe from neutral to almost completely ionized. This is the period in the cosmic timeline when first sources of radiation formed and through the combination of various physical processes, reionized the Universe. Unfortunately, the details of these processes as well as the nature of ionizing sources are poorly constrained. Thus it is right time to look for probes that enhance our understanding about this crucial epoch. Global redshifted 21-cm signal, also known as monopole component, from atomic hydrogen is potentially the richest probe to study EoR and preceding Dark Ages. It promises to better constrain nature of the first sources of radiation as well as thermal evolution of Inter-Galactic Medium. However, detection of this faint monopole component is challenging due to high precision required in instrumental calibration and modeling of substantially brighter foregrounds and instrumental systematics. In addition, ongoing experiments aiming for the detection of the signal use total power measurements. Such class of measurements suffer from receiver noise which, on an average, can be 10^4 times higher than signal of interest. In particular, modeling of receiver noise with mK accuracy and its separation remains a formidable task for such experiments. Interferometers do not respond to receiver noise; therefore, we explore here the theory of the response of interferometers to global signals. In other words, we discuss the spatial coherence in the electric field arising from the monopole component of the 21-cm signal and methods for its detection using sensor arrays. We proceed by first showing that interferometers do respond to monopole component of the signal, contrary to the general belief. We study the response to uniform sky of two-element interferometers made of unit dipole and resonant loop antennas, then extend the analysis to interferometers made of 1-D arrays and also consider 2-D aperture antennas. We discuss the configurations that are conducive to the detection of monopole component of the signal. We observe that the maximum response, with most favorable configuration, is 1/5th of the total power measurement. This requires that integration time for such configurations be 25 times more than that of total power measurement. Hence we describe methods by which the coherence might be enhanced so that the interferometer measurements yield improved sensitivity to the monopole component. We conclude that (a) it is indeed possible to measure the global 21-cm from EoR using interferometers,(b) a practically useful configuration is with omnidirectional antennas as interferometer elements, and (c) that the spatial coherence may be enhanced using, for example, a space beam splitter between the interferometer elements.

ASI 2016 – Abstract Book 5

ASI-2016 Parallel Session - Tuesday, 10 May, 2016

Time: 16:00 - 17:30 Venue: EMMRC Auditorium

Stars, The Milky Way Galaxy and its Neighbours-I [Chairperson: Annapurni Subramaniam]

ASI2016_417 Tapas Baug 16:00–16.15 Oral

D.K. Ojha, TIFR, Mumbai. L.K. Dewangan, PRL, Ahmedabad. J.P. Ninan, TIFR, Mumbai.

Galactic bubble N37 and surrounding star formation activity

In spite of their vast importance in the evolution of their host galaxies, formation and evolution of massive stars are not yet well understood. They are the main source of heavy elements and ultra-violet radiations. They influence the galactic evolution and replenish interstellar medium by their strong winds, outflows, expanding H II regions and supernova explosions. Processes like "collect and collapse" and radiative driven implosion (RDI) found to occur around H II regions and lead to further star formation. Massive stars are often found to be associated with mid-infrared bubbles, elongated columns of gas (i.e, pillars) pointing towards the ionizing sources. Understanding the interplay between the ionizing radiation and surrounding dense gas is important for characterizing triggered star formation. We studied star formation activity around a Galactic bubble (N37; Churchwell et al., 2006) possibly developed by several massive stars. We analysed multi-wavelength data starting from optical to radio to look for detailed processes going on in this region. From our observed optical spectra from 2-meter Himalayan Chandra Telescope, we identified two sources as early-B/late-O type stars. It is apparent from the 20 cm Multi-Array Galactic Plane Imaging Survey (MAGPIS) map that the expansion of H II region has led to formation of this bubble. The bubble is also found to be associated with pillar-like structures. Pillars are generally formed because of shadowing the ionizing radiation by an inhomogeneous density field. These pillars are also believed to be probable sight of triggered star formation via RDI. Starlight polarization data provide the information about the orientation of the magnetic field on the plane-of-sky, and hence, alignment of dust particle. Variation in mean polarization position angle around the bubble is noticed in the GPIPS near-infrared H-band polarization, suggestive of expansion of the surrounding gas. A large scale accumulation (clump) of mass (> 30000 M_sun) at the edge of the bubble N37 is evident from the Herschel column density map and 13CO molecular line data. Young stellar sources, identified using Spitzer IRAC bands and UKIDSS NIR band magnitudes, are mostly seen towards the massive clump and at the edge of the bubble. Overall analysis of this region suggests that the presence of massive stars at the center of the bubble has probably induced triggered star formation on the surrounding material.

ASI 2016 – Abstract Book 6

ASI2016_522 Lokesh Kumar Dewangan 16:15–16.30 Oral

Dewangan, L. K. (PRL, India), Mayya, Y. D. (INAOE, Mexico), Luna, A. (INAOE, Mexico) , and Ojha, D. K. (TIFR, Mumbai)

A multi-scale, multi-wavelength study of massive star-forming region W42

The identification of jet associated with a critical early phase of an individual O-type star is extremely rare phenomenon in massive star formation research. In the literature, there are only a handful of massive young stellar objects known to be associated with highly collimated jets and/or Herbig-Haro objects. We will present results of an analysis of massive star-forming region W42 using a multi-scale and multi-wavelength approach. These results throw light on the physical environment of W42 on smaller (about 5000 AU) and larger (about several pc) scales, helping to understand the formation of massive stars. In this region, we have discovered a parsec scale H2 outflow that is driven by an infrared counterpart of the 6.7-GHz methanol maser emission (i.e. W42-MME; stellar mass 19 solar mass and extinction 48 mag). Furthermore, we have investigated a collimated jet-like feature (in the inner 4500 AU) in W42-MME using the VLT near-infrared adaptive-optics images. The jet is located inside an envelope/cavity (extent ~10,640 AU) that is tapered at both ends and is oriented along the north-south direction. Such observed morphology of the outflow cavity around the massive star is scarcely known and is very crucial for understanding the jet-outflow formation process in massive star formation.

ASI2016_749 Jessy Jose 16:30–16.45 Oral

Gregory H. Herczeg (Kavli Institute for Astronomy and Astrophysics), Jinyoung S. Kim (University of Arizona), Manash R. Samal (Laboratoire d'Astrophysique de Marseille)

Effect of stellar feedback on subsequent star formation activity

One of the unsolved questions in the field of star formation concerns the effect that environment, in particular the stellar feedback may have on the subsequent star formation process. Numerical simulations show that the effect of stellar feedback in a massive star forming region depends upon several factors such as the amount of input radiation and wind energy, properties of the surrounding molecular cloud etc. As a result, the feedback effect on star formation activity may vary from region to region. In this context, star formation activity within a few, relatively distant (~2 kpc) massive star forming regions, which are thought to be evolving under the influence of massive stars have been performed. Using deep near-IR and mid-IR imaging data, we made a systematic analysis to obtain the census of young stellar objects and gas density structure of these regions. The combination of column density maps and stellar census lets us estimate the star formation efficiency and star formation rate of these regions. With the uniform data sets, we explore how the star formation properties at different parts of individual regions vary with respect to the dense gas fraction as well as the amount of input energy from massive stars. Our analysis suggests that the star formation history and dense gas fraction play important role in determining the global star formation properties of individual star forming regions. The stellar feedback from massive stars seems to be influencing only to its more localised neighbourhood and may not have measurable effect on the global star formation activities of the regions in this study.

ASI 2016 – Abstract Book 7

ASI2016_716 Kaushar Vaidya 16:45-17:00 Oral

Wen-Ping Chen,National Central University, Taiwan; Hsu-Tai Lee, Tainan Astronomical Education Area, Taiwan

Optical Spectroscopy of X-ray Selected Young Stars in the Carina Nebula

We present low-resolution optical spectra for 29 X-ray sources identified as either massive star candidates or low-mass pre-main-sequence (PMS) star candidates in the clusters Trumpler 16 and Trumpler 14 of the Carina Nebula. Spectra of two more objects (one with an X-ray counterpart, and one with no X-ray counterpart), not originally our targets, but found close (∼3″) to two of our targets, are presented as well. Twenty early-type stars including an O8 star and seven B1-B2 stars, and eleven T Tauri stars, are identified. Most early-type stars are non-variable in X-ray emission. The X-ray hardness ratios of T Tauri stars are found to be consistent with those of the Orion T Tauri stars. The mean V-band photometric variability of T Tauri stars, is found to be ~0.1 mag, significantly larger than the mean V-band variability of all stars, ~0.04 mag. The addition of one O star and seven B1–B2 stars reported here contributes to an 11% increase of the known OB population in the observed field. The 11 T Tauri stars are the first ever confirmed low-mass PMS stars in the Carina Nebula region.

ASI2016_550 Aruna Goswami 17:00-17:15 Oral

Aruna Goswami IIA Bangalore

Carbon-Enhanced Metal-Poor stars: evolution, nucleosynthesis, observations and the impact on cosmochemistry Carbon-enhancement phenomena appear in stars that exhibit four different heavy-element abundance patterns. The most numerous class is characterised by enrichments of neutron-capture elements with an abundance pattern compatible with the operation of the s-process in asymptotic giant branch (AGB) stars. Another class exhibits large overabundances of elements produced by s-process and also overabundances of elements whose origins are traditionally related to r-process. The Carbon-enhanced metal-poor stars (CEMP) that do not show enhancement of heavy elements form another class, and, there is yet another class of CEMP stars that are characterized by r-process enhancement, although this later class has only one confirmed example till now. I will discuss how the chemical abundances observed in these stars are employed to unravel a variety of details and their implications for cosmochemistry.

ASI 2016 – Abstract Book 8

ASI2016_653 Susmitha Rani Antony 17:15 – 17:30 Oral

Sivarani, T. -IIA Bangalore Ninan, J. P - TIFR, Mumbai Ojha, D.K- TIFR, Mumbai Giridhar, Sunetra- IIA Bangalore HESP team- IIA bangalore

Oxygen abundances in carbon enhance metal poor (CEMP) stars: Comparison between CO and [OI] lines

Carbon enhanced metal poor stars are metal poor stars with [Fe/H] < -2.0 and [C/Fe] > 1.0. The origin of carbon in these stars are either due to binary mass transfer from an AGB companion or from an ISM polluted by faint early supernovae that went through mixing and fall back. Oxygen is one of the key elements that help to differentiate between these two scenario and also to probe the masses of the AGB companion. However, oxygen abundance in these are notoriously difficult due to the faint [OI] line at 6300Ang. The CO lines in the NIR spectra provides a practical solution to derive oxygen abundance in CEMP stars. In this work we compare oxygen abundances derived from CO lines using TIRSPEC and [OI] 6300Ang lines using HESP instruments on the 2m HCT.

ASI 2016 – Abstract Book 9

ASI-2016 Parallel Session - Tuesday, 10 May, 2016

Time: 16:00 - 17:30 Venue: Ibn Khaldoon Auditorium

Extragalactic Astronomy-I [Chairperson: Somak Raychaudhury]

ASI2016_577 SOUMAVO GHOSH 16:00–16.15 Oral

Prof. Chanda J. Jog (IISc) Tarun Deep saini (IISc)

Effect of Dark Matter halo on spiral structures of different scales

Low surface brightness (LSB) galaxies are known to be dominated by Dark Matter (DM) halo, starting from the very inner radii. Hence, LSB galaxies naturally offer a place to probe the effect of DM halo on galactic dynamics. We have investigated theeffect of dark matter halo on spiral structures of different scales, using the input parameters of UGC 7321, a typical superthin, LSB galaxy. For the small-scale structures, we found that the dominant dark matter halo suppresses the smallscale spiral structures almost completely, thus providing a natural explanation to the lack of strong flocculent arms in LSB galaxies. Next we also studied global modes which we find are not much affected by DM halo, when the galactic disc is modelled as fluid. However, since these LSB galaxies reside at the edge of the voids, or in isolated places and consequently galaxy encounters are less likely to occur. Therefore, although technically, the global spiral modes are allowed in both stars only and stars embedded in DM halo , the lack of galaxy interactions makes it unlikely for the largescale spiral structures to happen in real galaxies. REFERENCES: • Ghosh S. & Jog C. J., 2014, MNRAS, 439, 929 • Ghosh S., Saini T. D. & Jog C. J., 2015,in press, MNRAS,

ASI2016_581 SUVENDU RAKSHIT 16:15–16.30 Oral

Suvendu Rakshit, Romain Petrov, Florentin Millour, Stéphane Lagarde, Martin Vannier, Alessandro Marconi and Gerd Weigelt

First spatially resolved black hole mass of quasar 3C273

Understanding the broad line region is critical to understand geometry and kinematics of the central engine, accretion mechanism and to estimate mass of central supermassive black hole (SMBH). Reverberation mapping (RM) estimates SMBH masses using virial relation, which relies on a poorly known scale factor that depends on geometry and kinematic of the BLR. Using “Blind mode observation” at AMBER/VLTI, for the first time it has been possible to resolve the BLR of quasar 3C273 in Pa-alpha. The first result shows a drop in differential visibility indicating an extended BLR much larger than RM prediction. A global fit to the 3C273 data shows that the Pa-alpha BLR is extended beyond the dust inner-rim, which is inclined close to face-on and has a spherical structure, where Keplerian rotation and macro-turbulent velocities have similar contribution. The mass of SMBH in 3C273 is found to be 4.8e8 solar mass and the scale factor to be about 3.

ASI 2016 – Abstract Book 10

ASI2016_524 Kartick C Sarkar 16:30–16.45 Oral

Kartick C Sarkar, Raman Research Institute, Bengaluru, India. Biman Nath, Raman Research Institute, Bengaluru, India. Prateek Sharma, Indian Institute of Science, Bengaluru, India. Yuri Shchekinov, P. N. Lebedev Physical Institute, Moscow, Russia.

Multi-wavelentgh emission from galactic winds and Fermi Bubbles

Modelling of emission from multiphase galactic outflows is important to decipher the feedback processes in galaxies. Fermi Bubbles (FBs) are excellent laboratories for such studies as they shine in radio, x-ray, gamma rays and also show kinematic signatures in UV absorption. Based on hydrodynamical simulations, we have studied the origin of FBs and related multi-band emissions. We show that a star formation rate (SFR) of 0.5 Msun/yr at the Galactic centre can give rise to the FBs over a time scale of ~30 Myrs. By modelling X-rays, we constrain the circum-galactic medium (CGM) density of our Galaxy to be ~2e-3 m_p/cc. Modelling of radio and gamma rays, using synchrotron and inverse Compton emission, shows that the magnetics field inside the bubbles is ~3\muG. Our model also provides explanation of the observed kinematics of absorption lines through the FBs. Not only from our Galaxy, X-rays from other star forming galaxies also can be related to the hot phase of the galactic wind. Recent observations show that diffused soft X-ray luminosity (Lx) \propto SFR^{1/3}, with large scatter at lower end of SFRs. We show that this relation can be well understood as the X-ray emission coming from the central star-forming region (Lx \propto SFR^2), and the CGM (Lx ~ constant). Our analysis shows that at higher SFRs (>~ few Msun/yr) the X-ray emission from the central region dominates, whereas, for lower SFRs (<~ 1 Msun/yr) the emission is dominated by the CGM. This approach naturally explains the observed stellar mass dependence of Lx and a large scatter at low SFR end.

ASI2016_763 Vikas Chand 16:45-17:00 Oral

1.A.R. Rao, 2.Rupal Basak, 1.TIFR Mumbai 2. Centrum Astronomiczne im. M. Kopernika PAN Warsaw, Poland

SPECTRAL STUDY OF GAMMA RAY BURSTS USING CZTI OF ASTROSAT

Astrosat captured a GRB on its first day. This GRB occurred on 06 Oct, 2015 and named as GRB151006A was also observed in Fermi and Swift satellites. We will be presenting the spectral time integrated, time resolved fitting of various GRB models to this GRB and also lightcurve fitting to models in different time cuts and energy bands. The results of simultaneous spectral analysis the CZT imager ( which is one of the instrument on-board Astrosat ) data along with Fermi and Swift missions instruments, will also be presented in a poster.

ASI 2016 – Abstract Book 11

ASI2016_773 Indranil Chattopadhyay 17:00-17:15 Oral

Seong Jae Lee, Rajiv Kumar, Dongsu Ryu, Hyung Siek

Simulation of accretion disc and multiple shocks

We simulate viscous, advecitve accretion disc around black holes. We show for large amplitude primary shock oscillation, the flow develops multiple inner, secondary shocks. This results in irregular oscillation and episodic mass outflow rates. As a result, we show that the mass outflow rate can be related with the QPO.

ASI2016_880 Rupak Roy 17:15 – 17:30 Oral

N/A

Luminous Supernovae : Implication of shock interaction on the observed properties

This is now established that the life of every massive star ends through a violent explosion, know as Core- Collapse Supernova (CCSN). In last couple of decades both theories and observational skills had been developed to understand the diversities of the CCSNe along with their origins and after-effects. In the most common scenario the core of such a star collapses under self-gravity and forms a compact object, while the outer shells are thrown away in the form of a cosmic catastrophic event. After the year 2005, dedicated surveys like CRTS, LOSS, ROTSE, PTF, PanSTARRS have discovered several events which have an average absolute Visual-band peak magnitude of about -21 mag, more than 2 mag brighter than CCSNe. These are Superluminous SNe (SLSNe). It seems that SLSNe are neither occurring in the nearby universe, nor are they hosted in massive-galaxies like our Milky Way. The mechanism for SLSNe is still not well understood. The circumstellar interaction or emergence of a magnetar after core-collapse or disruption of a massive star through pair production are the proposed scenarios. It is also not clear whether by origin the progenitors of CCSNe and SLSNe are same or are they different. Recent research revealed that there are few events which come in between these two classes. These gap-transients are important to constrain the nature of the progenitors of these two different populations as well as their environments and explosion mechanisms. In this contribution, we will discuss about the impact of circumstellar interaction on the observed properties of luminous supernovae. We will also discuss about the probability to detect such objects at early phases from the ground and space-based observatories and the importance of such study to understand the massive stars in the near and far universe.

ASI 2016 – Abstract Book 12

Wednesday, May 11, 2016

ASI-2016 Plenary Session

ASTROSAT- First Science Results [Chairperson: Swarna Ghosh]

Time: 9.30 am – 11.30 am Venue: Convocation Complex

ASI2016_640 S. N. Tandon 9.30 am - 9.54 am Plenary

Calibrations of UVIT and the first scientific results

UVIT (Ultraviolet Imaging Telescope) is a payload in ASTROSAT. It provides simultaneous imaging in FUV (130-180 nm), NUV(200-300 nm), and VIS(320-550 nm) over a field of ~ 28'. The spatial resolution of the ultraviolet images is < 1.8" and that of VIS images ~ 2.4". Slitless spectroscopy with a resolution of ~ 100 is also possible in the ultraviolet bands. ASTROSAT was launched on September 28, 2015, and UVIT started observing on November 30, 2015. Preliminary results from the initial observations for calibrations indicate that the primary parameters (e.g. spatial resolution and sensitivity) of the payload are matching the design- specifications. Detailed results of the calibrations and preliminary results from first scientific observations would be presented in talk.

ASI2016_630 K. P. Singh 9.54 am - 10.18 am Plenary

First Scientific Results from observations with the Soft X-ray imaging Telescope onboard ASTROSAT

Soft X-ray imaging Telescope (SXT) onboard the AstroSat is India's first X-ray imaging telescope. SXT was made fully operational on October 26, 2015. I will describe the characteristics of the SXT, and the first scientific results obtained from the observations carried out during the performance verification phase of the SXT.

ASI 2016 – Abstract Book 13

ASI2016_776 M. C. Ramadevi 10.18 am - 10.42 am Plenary

SSM on ASTROSAT: First Results

SSM onboard ASTROSAT is an X-ray sky monitor with a large FOV to scan the sky to detect and locate transient X-ray sources in the soft X-ray energy band of 2 to 10 keV. SSM comprises of 3 units of position sensitive proportional counters with 1D coced mask on each unit to do imaging. All three units are mounted on a platform capable of rotation so that the instrument sacns the sky in step and state mode. It stares at every FOV for 10 min and steps by 10 deg and thus capable of covering 50% of the sky in one full rotation of the platform. This talk will address the details of the instrument and the first results from the instrument onboard.

ASI2016_644 J. S. Yadav 10.42 am - 11.06 am Plenary

Large Area X-ray Proportional Counter (LAXPC) instrument onboard ASTROSAT

ASTROSAT India's first dedicated astronomy space mission was launched on September 28, 2015. The LAXPC instrument became fully operational on 19th October 2015 for the first time in space. The Large Area X-ray Proportional Counter (LAXPC) is one of the major payloads on ASTROSAT. A cluster of three co-aligned identical LAXPC detectors provides large area of collection of about 8000 cm2. The large detection volume (15 cm depth) filled with mixture of xenon gas (90(%) and methane (10%) at ~ 2 atmospheres pressure, results in detection efficiency greater than 50%, above 30 keV. The LAXPC instrument is best suited for X-ray timing and spectral studies over energy range of 3-80 keV. It will provide the largest effective area among all the satellite missions flown so far worldwide and will remain so during next 5-10 years for X-ray studies in the given energy range. GEANT4 simulation for LAXPC detectors was carried out to understand detector background and its response. We have performed detector calibration in orbit. The LAXPC instrument is functioning well and has achieved all detector parameters proposed initially. In this paper, we will describe LAXPC detector calibration in lab as well as in orbit along with results.

ASI2016_1031 S. Vadawale 11:06 am - 11:30 am Plenary

Initial results from Astrosat CZTI

The Cadmium Zinc Telluride Imager (CZTI) is a wide-field coded aperture mask instrument on Astrosat, sensitive to photons from 20 keV to over 150 keV. It is primarily designed for simultaneous hard X-ray imaging and spectroscopy of variety of celestial X-ray sources such as, black hole binaries, neutron star binaries, pulsars, AGNs and GRBs. The detector plane of CZTI consists of total 64 CZT detector modules arranged in four identical quadrants. Each detector module has an active area of 16 cm2 and further divided into an array of 16 ? 16 pixels, resulting in total 16384 pixels over entire detector plane. As an added advantage, the fine pixilated nature of the detector plane of CZTI is also helpful in extending useful energy range to ~250 keV as well as to measure polarization in hard X-rays, by identifying the X-ray photons interacting by means of Compton scattering. CZTI was the first scientific payload of Astrosat to be switched on after one week of the launch and was made operational during subsequent week. First phase of the CZTI performance verification observations consisted of deep imaging observations of the standard candle source, the Crab nebula as well as a black hole binary Cygnus X-1. Here I will discuss the in-orbit performance of CZTI and present preliminary results form the performance verification phase observations.

ASI 2016 – Abstract Book 14

ASI-2016 Parallel Session - Wednesday, 11 May, 2016

Time: 12:00 - 13:30 Venue: Ibn Khaldoon Auditorium

Extragalactic Astronomy-II [Chairperson: Suchetana Chatterjee]

ASI2016_744 Lijo Thomas George 12:00–12:15 Oral

K. S. Dwarakanath (RRI), M. Johnston-Hollitt (VWU), H. Intema (Leiden), N. Hurley-Walker (Curtin), L. Pratley (VWU) et al.

Low Frequency Study of Merging Galaxy Clusters using the MWA

Diffuse radio emission from galaxy clusters is seen in the form of central halos or peripheral arc-like relics. Clusters that exhibit signs of merging activity are more likely to host these halos and relics than those that don't. With a motivation to understand the formation of halos and relics in galaxy clusters we have studied 9 clusters using the data from the Murchison Widefield Array. Either double or single relics have been detected in these clusters from earlier higher radio frequency (1400 MHz) observations. In addition, radio haloes have also been detected in 4 of these clusters at 1400 MHz. We have analysed the images of these clusters from the GaLactic and Extragalactic All-sky MWA (GLEAM) Survey at 5 frequencies (88, 118, 154, 188 and 215 MHz). Furthermore, we have made a detailed comparison of the MWA images of these clusters at 154 MHz with those created by us from archival data of the 150 MHz GMRT Sky Survey (TGSS). We have estimated the spectra of all the relics in the frequency range 80--1400 MHz and are exploring the implications to the synchrotron lifetimes of the relics and to the dynamical timescales of the cluster merger. We have also detected the known halo emission in 4 of these clusters and established their spectra over the range 80--1400 MHz. Additionally, we have obtained stringent upper limits to the halo emission in the remaining clusters. We discuss these preliminary results and the implications of the spectra of the relics and the limits on the halo emission for cluster formation and merger history.

ASI 2016 – Abstract Book 15

ASI2016_862 Deovrat Prasad 12:15–12:30 Oral

1.Prateek Sharma, Indian Institute of Science, Bangalore, India 2. Arif Babul, University of Victoria, Victoria, Canada

Role of cooling and AGN jets in the evolution of cool-core galaxy clusters

The existence of cool cores with short cooling times in galaxy clusters is a long-standing puzzle. According to the classical cooling flow model, cluster cores with short cooling times are expected to cool catastrophically and to fuel star formation at a rate of 100–1000 M_sun/yr. However, cooling, dropout, and star formation at these high rates are never seen in cluster cores. AGN jets have been suggested as a possible solution for this puzzle as they have sufficient energy to replenish the cooling losses. We perform 3D and 2D (axi-symmetric) hydrodynamic simulations in spherical geometry, to study the evolution of cool cluster cores heated by feedback-driven bipolar active galactic nuclei (AGNs) jets. Since, Bondi Accretion is in-efficient, cold gas feedback emerges as the primary mechanism for feeding the central Super Massive Black Hole (SMBH). Condensation of cold gas, and the consequent enhanced accretion, is required for AGN feedback to balance radiative cooling with reasonable efficiencies, and to match the observed cool core properties. However, cold gas has angular momentum and settles down in torus around SMBH. We study the distribution of angular momentum of the cold gas and its implication on the cold feedback model.

ASI2016_659 Pradeep Chandra 12:30-12:45 Oral

P Chandra, K K Yadav, K K Singh, R C Rannot, A K Tickoo, A Goyal, K K Gour, N K Agarwal , H C Goyal, N Kumar, P Marandi, M Kothari, V K Dhar, N Chouhan, C Borwankar , B Ghosal, S Bhattacharyya, N Bhatt, S Sahayanathan, M Sharma, S Godambe, N Mankuzhiyil, K Chanchalani, K Venugopal, S Godiyal, R Koul, M K Koul, C K Bhat

VHE gamma-ray observations of Markarian 421 and B20806+35 using TACTIC during 2015-16.

The TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) is a gamma-ray telescope located at Mount Abu Rajasthan (1300 m asl) to explore the very high energy (VHE, E>100 GeV) gamma-ray sky with an energy threshold of ~ 850 GeV. In this work, we present results from VHE gamma-ray observations of two blazars namely Mrk 421 (z=0.031) and B20806+35 (z=0.083) with TACTIC telescope performed during 2015-16 campaign. We complement the results of TACTIC with near simultaneous data from Fermi-LAT (Large Area Telescope) observations of the above sources to understand the high energy gamma-ray emission in the energy range 100MeV-300GeV. We also include contemporary archival data from X-ray, optical and radio observations for multi-wavelength study of the above source.

ASI 2016 – Abstract Book 16

ASI2016_690 Rubinur Khatun 13:00 – 13:15 Oral

Mousumi Das Preeti Kharb Indian Institute of Astrophysics, Bangalore

Radio Observations of Candidate Dual Active Galactic Nuclei in Double Peaked Emission Line Galaxies

We present results from arcsecond-scale radio observations with the Expanded Very large Array (EVLA) of eight galaxies classified as double peaked emission line active galactic nuclei(DPAGN). Our main aim is to distinguish between dual AGN and jets or disks in these DPAGN. Dual AGN or supermassive black hole (SMBH) binaries are expected to form during galaxy mergers and minor accretion events. When the SMBHs are accreting, they become dual AGN. Double peaked emission lines can indicate the presence of two AGN, but can also be due to powerful bipolar jets or outflows or rotating nuclear disks. High resolution radio or X- ray observations are the best way to confirm the presence of binary AGNs. In our 6 GHz observation of the nuclei of eight DPAGN galaxies, we have detected two double core sources that appear to be dual AGN and four extended sources that are possibly radio jets associated with compact cores. The remaining two galaxies are single compact cores. We have used archival data at higher frequencies to do follow-up studies of one of the double core galaxies. Our results suggest that high resolution, multi-frequency radio observations are essential to detect dual SMBHs in our low redshift Universe.

ASI2016_695 Zahir Ahmad Shah 13:15 – 13:30 Oral

Pankaj Kushwaha (IUCAA), Sunder Sahayanathan(BARC Mumbai), Naseer Iqbal (Kashmir University), Ranjeev Misra(IUCAA)

Multi-Wavelength Study of 3C454 During August 2015 Flaring

Blazars are the most powerful, highly energetic and rapidly varying at all wave-band radio loud AGN‟s. They are known to posses the extremely collimated relativistic jets pointing towards the line of sight of observer, leading to the Doppler boosting of the Blazar jet emission. Blazars are classified as Bl-lacs and FSRQs based on the absence/weak or presence of emission lines in the optical band respectively. 3C454.3 is one of the most active, variable and powerful gamma ray emitter FSRQ (also catalogued as PKS 2251+158; z = 0.859). Over the years multiple episodes of gamma ray outbursts have been reported. A detailed study of recent flaring activity of Flat Spectrum Radio Quasar (FSRQ) 3C454 observed simultaneously in Gamma-ray, X-ray and Optical by various astronomical observatories during the period 2015 Aug 16- 2015 Aug 28 has been carried out during the period 2015 Aug 16- 2015 Aug 28. During this flaring highest flux of 1.8459162052×10−05 ±1.8198335927×10−06 photons/cm2/s was observed at MJD 57256.0625116 in a 3-hour binning. Also in the six hour binning we recorded a maximum gamma ray flux of 1.74111666309 × 10-05 ± 0.1306×10−05 photons/cm2/sec at MJD 57256.13. The multi-wavelength light curve obtained shows the source is highly variable and will help in diagnosing the location of emission region and physical mechanism responsible for the emission. Compared to one day binning light curve, where only one flaring event is visible, the six hour binning Fermi light curve being finer shows the outburst is composed of two consecutive flares characterized by rise and decay time scales of a day. These two successive flaring events are more visible in 3-hour binning light curve. We have selected three regions from the multi-wavelength light curve via Flaring region, Post flaring and quiescent region to have SED characteristic of the flaring during August 2015.

ASI 2016 – Abstract Book 17

ASI-2016 Parallel Session - Wednesday, 11 May, 2016

Time: 12:00 - 13:30 Venue: Biotechnology Auditorium

Sun and Solar System-I [Chairperson: Dipankar Banerjee]

ASI2016_785 K. Chenna Reddy 12:00–12:15 Oral

G Yellaiah Department of Astronomy, Osmania University, Hyderabad – 500 007

Strengths and limitations of the Gadanki MST radar for meteor observation

There is a increasing interest in the effects of meteors on the upper atmosphere and ionosphere. The use of narrow beam MST radar for detection of meteoric phenomena is a proven technique that has number of avenues to be explored. The use of MST radars allows us to study the meteor population which probably contributes the most extraterrestrial material to the Earth‟s upper atmosphere. In spite of its installation about two decades ago, only few meteor observations have been made at the Gadanki MST radar. The purpose of this paper is to highlight the strengths of the Gadanki radar for meteor observations. Since the transmitter output power of this radar is approximately 40 times higher compared to the output power of classical meteor radars, hence a direct probing with improved sampling resolution is possible. A better understanding of the limitations associated with narrow beam MST radar system is important for comparison studies of meteor activity with other observational instruments. In addition we present here characterisation of the meteor reflections process and the corresponding signal analysis for some of the echoes.

ASI 2016 – Abstract Book 18

ASI2016_452 Gurpreet Kaur 12:15–12:30 Oral

Prof. Sandeep Sahijpal, Panjab University, Chandigarh

Modelling the thermal evolution and differentiation of interior of Mars and Mercury

The small size of Mars and Mercury as compared to other terrestrial planets is a big puzzle in terms of theories developed earlier to study planet formation processes. Despite of small size of Mercury (radius ~ 2440 km), its unusual high density (~5.44 g cm-3) as compared to other terrestrial planets like Earth (~4.1 g cm-3) and Mars (~3.7 g cm-3) is still a mystery. The recent results of MESSENGER mission to Mercury have challenged the results of theories developed earlier to understand the high density of Mercury with large iron core at the center. In the present work, we have studied the thermal evolutionary criteria of Mars and Mercury in the initial 50 Ma (million years) of the formation of solar system by incorporating the heat produced due to short lived radio-nuclides 26Al and 60Fe along with long-lived radionuclides 40K, 235U, 238U and 232U. To study the thermal evolution of Mars, we assumed Mars to be formed from planetesimals with H-chondritic composition. Partial differential equation of heat transfer was solved numerically assuming radiogenic heat along with the accretion heat produced during the growth planet. The pressure dependent liqidus and solidus temperature of iron and silicate were calculated at each spatial point inside Mars. Stoke‟s law was used to calculate the descend velocity of metallic blobs to form iron core at the center. Apart from radiogenic and accretion heat, we have also parametrically incorporated the heat produced due to gravitational energy released during the core-mantle differentiation inside Mars. We also performed one simulation to understand the thermal evolution of Mars assuming a low value of (26Al/27Al)initial due to recent results showing the possibility of heterogeneity of 26Al in the solar nebula. From the results of thermal evolutionary study of Mars, we conclude that accretion energy alone cannot produce large scale heating, melting and differentiation of Mars. The results show that 26Al played the major role among all the heat sources in planetary scale differentiation of Mars within the initial ~1.5 million years. This seems to be consistent with the chronological records of Martian meteorites found on Earth. To study the thermal evolution of Mercury, we considered two types of models. In first type of model (Model A), we considered Mercury to be formed from accretion of planetesimals having Enstatite composition with final radius 2440 km. In the second model (Model B), we considered Mercury to be having radius comparable to radius of Mars(~3440 km) accreted from planetesimals with H-chondritic composition which subsequent to differentiation into iron core and silicate mantle, suffered impact induced stripping of its mantle leaving a large iron core at the center. The results of numerical simulations of Mercury show that heat produced due to short-lived radionuclides along with accretion energy could have resulted in the large scale heating and melting inside Mercury if Mercury accreted early during the formation of solar system. Acknowledgements: This work is supported by PLANEX (ISRO) research grant.

ASI 2016 – Abstract Book 19

ASI2016_793 Ayesha Maryam Mazarbhuiya 12:30-12:45 Oral

1.Parizath Deb Roy,Assam University 2.Himadri Sekhar Das,Assam University 3.Biman J. Medhi,Aryabhatta Research Institute of Observational Sciences

Imaging polarimetric study on Comet 32P/Comas-Sola

Imaging polarimetric study on Comet 32P/Comas-Sola A. M. Mazarbhuiya 1a , P. Deb Roy 1b , H. S. Das 1c and B. J. Medhi 2 1 Department of Physics, Assam University, Silchar 788011, India 2 Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263129, India a [email protected], b [email protected], c [email protected] d [email protected] Abstract Comets are the small celestial body several km in diameter constituted mainly of water, ice and rock. They spend almost all their time at great distances from the Sun. The cometary activity starts when it approaches towards the Sun. In some cases, it becomes brighter and spectacular with coma and tail. Imaging polarimetry of comets gives a well-defined idea about the basic physical properties of cometary dust grains which are present in the coma and undergo a continuous evolution with distance from the nucleus during the entire period of cometary activity. The measurement of polarization of scattered radiation from comets provides an excellent tool to study cometary dust properties. The study of the cometary dusts gives useful information about the leastprocessed and pristine materials of early solar nebulae from which the present-day solar system has been evolved. In this paper, a short periodic Comet 32P/Comas-Sola with an orbital period of 9.5 years is studied through imaging polarimetry .The inclination of the orbit is about 9o.9 with the ecliptic plane. The perihelion distance of the comet was 2.0 AU on 17th October 2014 and its aphelion distance was 7.02 AU. The optical polarimetric observations were carried out during its closest approach to the earth at a distance of about 1.35 au by using 1.04-m Sampurnanand Telescope of Aryabhatta Research Institute of Observational Sciences (ARIES),Nainital on 20 th February, 2015. The polarization values obtained for Comet 32P/Comas sola is found to be almost uniform with the change of aperture which is pointing towards significant dust domination that overpowers the influence of gas.

ASI 2016 – Abstract Book 20

ASI2016_649 Rohit 12:45 – 13:00 Oral

Rohit Sharma NCRA-TIFR, Pune Divya Oberoi NCRA-TIFR, Pune

Characterisation of non-thermal solar emissions at low radio frequencies.

Murchison Widefield Array (MWA) located in Western Australia is an excellent instrument for spectroscopic solar imaging at meterwavelengths (80-300 MHz). The MWA solar dynamic spectra show weak features, typically spanning order a MHz and lasting a few seconds. These features are seen even during periods of low solar activity and their short temporal and spectral spans imply a non-thermal origin. Their characteristics are unlike those of any of the usual known types of solar bursts, but come closest to being heavily scaled down versions of type III bursts. In 1963 Parker hypothesised the presence of nanoflares as a solution to the coronal heating problem. These nanoflares are small flare events arising from magnetic reconnection, and a large number of them are required to routinely take place in the twisted and tangled coronal magnetic field carpet. A statistically steady background arising from a large number of such weak flares is meant to provide the missing coronal heat flux. No direct observations of nanoflares have been made yet . We explore the possibility that the weak non-thermal emissions observed in MWA data are radio signatures of nanoflares. As a step towards this, we have developed a technique to quantify the frequency of occurrence of such emission and its strength. This technique takes as an input flux calibrated dynamic spectrum for a carefully chosen MWA baseline, and decomposes it into a thermal and non-thermal parts. We model the observed emission as comprising of a thermal and non-thermal components. For calibrated data, over short spectral and temporal spans, the thermal emission will follow a Gaussian distribution while the non-thermal emissions will fall outside this Gaussian. In order to quantitatively separate these two we use the Gaussian mixtures technique. This technique models the data as a sum of many Gaussians and associated a probability with each data point of it being a part of each of the Gaussians in the model. We present our results from applying this technique to an hour of solar data from 3 September, 2013 (03:40-04:40 UT).

ASI2016_865 Kumar Venkataramani 13:00 – 13:15 Oral

Kumar Venkataramani(PRL, IIT-Gn) Shashikiran Ganesh(PRL) U.C.Joshi(PRL) Satyesh Ghetiya(IIST, PRL) K.S.Baliyan(PRL)

Study of Molecular Gas Emissions from Cometary Coma

The cometary coma is a mixture of gas and dust particles. It is rich in carbon-chain molecules, amino group, molecular hydrogen, cyanide molecules, atomic oxygen and various other products. Cometary spectra in the visible region are dominated by the presence of strong emission lines from these molecules. By investigating these emission lines and estimating the production rates and scale lengths of these molecules, we can get a better understanding of evolution of the cometary coma as it travels in its orbit around the sun. The optical spectra of some of the long period comets e.g. C/2014 Q2(Lovejoy), C/2013US10 (Catalina) and C/2013 X1(PANSTARRS) were obtained using a low resolution spectrograph mounted on the 0.5m telescope at the Mount Abu Infra-Red Observatory. Observations were carried out at different epochs and hence different helio-centric distances. The spectra of these comets were studied to model the spatial distribution of the molecules. We would like to present some of the interesting results of this study.

ASI 2016 – Abstract Book 21

ASI2016_583 Avyarthana Ghosh 13:15 – 13:30 Oral

Durgesh Tripathi (IUCAA), G. R. Gupta (IUCAA), V. Polito (DAMTP, University of Cambridge, UK ) , H. E. Mason(DAMTP, University of Cambridge, UK )

Fan Loops Observed by IRIS, EIS and AIA

Fan loops (formed between 0.6 to 1 MK temperature range) are one of the most complex and longest-living features emanating from the edges of an active region. They play an integral role as conduits of mass and energy amongst the various layers of the solar atmosphere (from the photosphere to the upper corona). Hence, measuring the physical parameters at the points where these fan loops are rooted as well as along their length is important. Spectroscopic data from the EUV Imaging Spectrometer (EIS) and the Interface Region Imaging Spectrometer (IRIS) have been used to study the morphology and dynamics of the plasma in these loops. Further we have incorporated AIA and HMI images in this work.

ASI 2016 – Abstract Book 22

ASI-2016 Parallel Session - Wednesday, 11 May, 2016

Time: 14:30 - 16:00 Venue: Ibn Khaldoon Auditorium

General Relativity and Cosmology-I [Chairperson: N. Panchapakeshan]

ASI2016_668 ABHIRUP GHOSH 14:30 – 15:00 Oral

Archisman Ghosh, Nathan K. Johnson-McDaniel, and Parameswaran Ajith (ICTS,TIFR), Walter Del Pozzo (University of Birmingham), David A. Nichols (Cornell University), Yanbei Chen (California Institute of Technology)

Testing general relativity using golden black-hole binaries

Binary black hole (BBH) coalescences are among the most energetic events in the Universe, where a considerable fraction of the binary's mass and angular momentum is radiated as gravitational waves (GWs). A “golden” BBH is a system for which the inspiral, i.e, when the black holes are spiralling towards each other, and ringdown, when the final black hole is settling down to a stationary state, are both well in the band of the detector. If a GW signal from such a system, is observed with good enough signal-to-noise ratio, the masses and spins of the binary black holes can be estimated just from the inspiral part of the signal. Given the estimates of the initial parameters of the binary, the mass and spin of the final black hole can be uniquely predicted making use of numerical-relativity simulations. In addition, the mass and spin of the final black hole can be independently estimated from the ringdown part. If General Relativity is the correct theory of gravity, these independent estimates have to be consistent with each other. We describe a Bayesian implementation of such a test of General Relativity (GR) that would make use of upcoming GW observations. We also show that this test is sensitive to GR violations that are not constrained by observations of the double pulsar.

ASI 2016 – Abstract Book 23

ASI2016_658 Nisha Rani 15:00–15.15 Oral

Deepak Jain, Deen Dayal Upadhyaya College, University of Delhi, New Delhi 110015, India Shobhit Mahajan, Department of Physics & Astrophysics, University of Delhi, New Delhi 110007, India Amitabha Mukherjee, Department of Physics & Astrophysics, University of Delhi, New Delhi 110007, India Nilza Pires, Departamento de Física Teórica e Experimental, UFRN, Campus Universitário, Natal, RN 59072-970, Brazil

Parametric and nonparametric contraints on Transition redshift

The cosmokinematics approach is used to study the accelerated expansion of the Universe. This approach depends only on the assumption that Universe is described by the FRW metric and is homogeneous and isotropic at large scales. We parametrize the deceleration parameter, $q(z)$, to constrain the transition redshift ($z_t$) at which the expansion of the Universe goes from a decelerating to an accelerating phase. We parametrize $q(z)$ in three ways namely, $q_\I(z)=q_{\textnormal{\tiny\textsc{1}}}+q_{\textnormal{\tiny\textsc{2}}}z$, $q_\II (z) = q_\3 + q_\4 \ln (1 + z)$ and $q_\III(z)=\frac{1}{2}+\frac{q_{\textnormal{\tiny\textsc{5}}}}{(1+z)^2}$. A joint analysis of the age of galaxies, strong lensing and supernovae Ia data indicates that the transition redshift is less than unity. $z_t$ is further constrain using nonparametric method (LOESS+SIMEX). This also gives $z_t<1$. Value of $z_t$ from parametric and nonparametric method is consistent with each other.

ASI2016_700 Archisman Ghosh 15:30–15.45 Oral

Walter Del Pozzo (University of Birmingham); P. Ajith (ICTS-TIFR)

Prospects of estimating cosmological parameters from gravitational-wave observations of coalescing binary black holes. The measurement of cosmological expansion parameters relies crucially on the complex physics of electromagnetic sources like supernovae and it is significantly affected by the systematics of their calibration and detection. An independent measurement of these parameters will be of prime significance in testing the current cosmological paradigm. The expected observation of gravitational waves (GWs) with the second generation detectors opens up such a possibility. For GW signals from compact binary coalescences, one can estimate directly the luminosity distance to the source. If it is possible to associate the host galaxy of the merger event, one can use the redshift-distance relation to obtain the cosmological parameters. Recent work [arXiv:1108.1317 [astro-ph]] has shown that with few tens of observations of inspiral GW signals with a worldwide network of detectors, one can constrain the Hubble constant to an accuracy of a few percents. In this work, we estimate the expected constraints using future GW observations of the inspiral, merger and ringdown of binary black holes and try to lay constraints on the Hubble constant and the matter fraction of the universe.

ASI 2016 – Abstract Book 24

ASI2016_607 SHANKARANARAYANAN S 15:45-16:00 Oral

Jose Mathew (IISER-TVM)

Low scale Higgs Inflation with Gauss Bonnet Coupling

Recent LHC data provides precise values of coupling constants of the Higgs field, however these measurements do not determine its coupling with gravity. We explore this freedom to see whether Higgs field non-minimally coupled to Gauss-Bonnet term in 4-dimensions can lead to inflation generating the observed density fluctuations. We obtain analytical solution for this model and that the exit of inflation (with a finite number of e-folding) demands that the energy scale of inflation is close to Electro-weak scale. We discuss the constrains from PLANCK data.

ASI 2016 – Abstract Book 25

ASI-2016 Parallel Session - Wednesday, 11 May, 2016

Time: 14:30 - 16:00 Venue: EMMRC Auditorium

Stars, The Milky Way Galaxy and its Neighbours-II [Chairperson: G.C. Anupama]

ASI2016_925 Lalitha Sairam 14:30–14:45 Oral

Singh, K.P., Tata Institute of Fundamental Research Drake, S. A., NASA Goddard Space Flight Center Kashyap, V., Harvard-Smithsonian Center for Astrophysics

Magnetic activities in the outer atmospheres of RS CVn-type Binaries

The RS CVn binaries are a class of tidally locked, rapidly rotating close binaries typically composed of a chromospherically active G- or K-type star with a late-type subgiant or main-sequence companion. In my talk, I will present our results from a systematic and detailed study of coronal X-ray emission from the bright young pre-main-sequence RS CVn system -- HD 155555, using Chandra HETG/MEG gratings. This system is a triple star system composed of a G5 IV, K0 IV and M3V star. The G (HD 155555 A) and K stars (HD 155555 B) form a short-period binary system with an orbital period of 1.68 days, that has an M dwarf companion HD 155555 C 33'' away. Both HD 155555 AB and HD 155555 C are strong X-ray sources with log LX of 30.54 and 29.30 ergs/s, respectively. We have analysed the dispersed spectra of both HD 155555 AB and HD 155555 C using discrete temperature APEC models, and have constructed the emission measure distribution (EMD) using spectral line analysis (using the ATOMDB 2.0), We have also obtained the elemental abundances and discuss whether or not they exhibit the Inverse FIP effect typically seen in active stars. From an analysis of the He-like triplets of Si XIII, Mg XII and Ne IX, we have derived coronal electron densities of ~10E10 cm^-3. Finally, we compare our results for HD 155555 with those of other RS CVn systems, such as AR Lac, a much older binary system, and with TW Hya, which is a relatively younger single pre-main sequence star.

ASI2016_781 Arti Joshi 14:45–15:00 Oral

Arti Joshi and Jeewan C. Pandey Affliation- Aryabhatta Research Institute of observational sciencES, Nainital, 263002

Photometry and Polarimetry study of Cataclysmic Variables (CVs)

We present time-resolved photometry and linear polarimetry of the two cataclysmic variables 2MASS J01303186+6221324 and 2MASS J03451159+533514. We classify the system 2MASS J01303186+6221324 as a deeply eclipsing intermediate polar which exhibits a deep eclipse of 1.8 mag with orbital period of 3.58 hr. However, the orbital period of the system 2MASS J03451159+533514 is found to be 7.8 hr. We also report the polarimetric observations of these two systems, where the polarization data reveals same periods with those obtained from photometrically. The variations of linear polarization from ~1.0-6.0 per cent are seen over an orbital cycle, with a minimum around the time of eclipse for both system.

ASI 2016 – Abstract Book 26

ASI2016_508 Anindita Mondal 15:00-15:15 Oral

Prof. G. C. Anupama (IIA, Bangalore), Dr. U. S. Kamath (IIA, Bangalore), Dr. R. K. Das (SNBNCBS, Kolkata), Dr. Soumen Mondal (SNBNCBS, Kolkata).

Abundance analysis of the Recurrent nova RS Ophiuchi (2006 outburst)

We present an analysis of elemental abundances of ejecta of the recurrent nova RS Oph using optical and near- infrared spectra during 2006 outburst (12 February, 2006) taken from 2m HCT and 1.2m Mt Abu observatory. We took optical spectra of 10 epochs (21 & 24 Feb, 12 Mar, 3 Apr, 26 May, 19 Jul, 18 Aug, 17 Oct, 2006 and two quiscence period data on 5 Apr, 2005 & 26 Apr, 2007) and NIR spectra of 2 epochs ( 16 Mar & 2 Apr, 2006). We use CLOUDY photoionization code to generate synthetic spectra by varying several parameters. The model generated spectra are then matched with observed emission line spectra. We obtain the best fit model parameters through χ2 (chi-square) minimization technique. The best-fit model parameters are compatible with a hot white dwarf source with log(T_BB) of 4.45 – 6.4 K and roughly constant log(luminosity) of 36.9 – 37.1 erg s−1. From the analysis we find the following abundances (by number) of elements with respect to solar: He/He⊙ = 1.5 – 2.5, N/N⊙ = 10 - 12, O/O⊙ = 0.7 – 5.0, Ne/Ne⊙ = 0.5 – 2.0, Si/Si⊙ = 0.3 – 0.5, Fe/Fe⊙ = 0.7 – 3.8, Ar/Ar⊙ = 4.0 – 5.5, and Al/Al⊙ = 0.9 – 1.1, Ni/Ni⊙ = 1.5 – 2.0. We estimate an ejected mass in the range of 3.4 - 4.9 x 10−6 M⊙ which is consistent with observational results.

ASI2016_548 Mayukh Pahari 15:15 – 15:30 Oral

Ranjeev Misra, IUCAA, Pune J S Yadav, TIFR, Mumbai

Spectro-temporal analysis of X-ray binaries using LAXPC on-board ASTROSAT satellite

In this talk, I would like to present results from the energy spectral analysis of different X-ray binaries observed by Large Area X-ray Proportional Counter (LAXPC) on-board ASTROSAT satellite. The analysis includes identification of spectral states based on hardness ratio and fitted spectral parameters, identification of timing properties of the corresponding state and comparison of the spectral and timing properties of different X-ray binary systems with that observed from earlier mission like RXTE and contemporary mission like NuSTAR. Within the calibration and systematic uncertainties, the high energy LAXPC spectra, in the energy range 15.0-50.0 keV, shows significant improvement over RXTE spectra in the similar energy range. Along with its unprecedented timing capabilities, LAXPC clearly shows significant improvement in understanding the accretion and radiation mechanism during spectral state transition in X-ray binaries which I shall discuss in my talk.

ASI 2016 – Abstract Book 27

ASI2016_432 Gaurava K Jaisawal 15:30 – 15:45 Oral

Sachindra Naik (PRL, Ahmedabad) and Prahlad Epili (PRL, Ahmedabad)

Suzaku observations of the Be/X-ray binary pulsar GX 304-1

We studied the broad-band spectral and timing properties of Be/X-ray binary pulsar GX 304-1, using two Suzaku observations during its outbursts in 2010 and 2012. X-ray pulsations were detected at ~275 s during both observations. Pulse profiles of the pulsar were strongly energy dependent. Soft X-ray pulse profile was found to be multi-peaked (with absorption dips) which evolved into a single peaked profile at higher energies. Significant changes in pulse profiles were detected in hard X-rays. The pulse profiles above 35 keV show a sudden change in profile pattern with shifted (~0.3 pulse-phase) main dip. The broadband energy spectrum of the pulsar was well described with partial absorbed Negative and Positive Exponential cutoff (NPEX) continuum model with 6.4 keV iron emission line and a cyclotron absorption feature. The cyclotron absorption line was detected at ~53 and 50 keV during 2010 and 2012 Suzaku observations, respectively. We have found a marginal positive dependence between cyclotron line energy and luminosity during Suzaku observations. The phase-resolved spectroscopy was performed to study the changes in spectral parameters around the pulsar. It was found that the presence of additional matter at certain pulse phases of the pulsar cause the absorption dips or multi-peak structures in soft X-ray pulse profiles. The cyclotron energy and depth were significantly variable (<24 %) with pulsar-phases. The observed variation in the cyclotron line parameters during both observations can be explained as due to the effect of the viewing angle or role of the complicated magnetic field of the pulsar.

ASI2016_1066 Hyung Mok Lee 15:45 – 16:00 Oral

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Formation of Compact Binaries in Dense Star Clusters

The gravitational wave due to a coalescence of black hole binary was detected recently. Such binaries can be either formed via evolution of a binary system composed of two high mass stars or via dynamical interactions in dense star clusters. This talk focuses on the dynamical formation processes and the properties of such binaries.

ASI 2016 – Abstract Book 28

Thursday, May 12, 2016

ASI-2016 Plenary Session

Plenary session: Dynamical systems [Chairperson: K. Subramanian]

Time: 9.30 am to 11.00 am Venue: Convocation Complex

ASI2016_654 S. Sridhar 9.30 am - 10.00 am Plenary

The disruption of multiplanet systems through resonance with a binary orbit

Most exoplanetary systems in binary stars are of S-type, and consist of one or more planets orbiting a primary star with a wide binary stellar companion. It is observed that: (a) Planetary eccentricities and mutual inclinations can be large; (b) There are more single-planet systems than multiplanet systems. I will report on recent work in which we present a new mechanism that could explain items (a) and (b). This mechanism relies on a resonance between the binary orbital period and the orbital precession periods of the multiplanet systems. Resonant binary forcing results in dramatic outcomes ranging from the excitation of large planetary eccentricities and mutual inclinations to disruption of the multiplanet system until just one planet remains. Processes such as planetary migration can bring an initially non-resonant system into resonance. As it does not require special physical or initial conditions, binary resonant driving is generic and may have altered the architecture of many multiplanet systems.

ASI2016_635 J. S. Bagla 10:00 am - 10:30 am plenary

Gravitational clustering in an expanding universe

I will describe the equations of motion for non-relativistic matter in an expanding universe and discuss generic aspects of dynamics and clustering. With the use of quasilinear approximations and spherical collapse, we can understand the key features of large scale structure. I will discuss the impact of dark energy on dynamics and growth of perturbations. It may be possible to probe characteristics of dark energy by studying dynamics in the vicinity of clusters of galaxies.

ASI 2016 – Abstract Book 29

ASI2016_638 Farooq Ahmed 10.30 am - 11.00 am Plenary

Gravitational Clustering of Galaxies: Derivation of distribution function using statistical mechanics of cosmology many-body problem Our understanding of large scale structures in the universe is based on the distribution of galaxies which we estimate from the probability distribution function. Galaxies Cluster on very large scales under the influence of their mutual gravitation and characterization of this clustering is problem of current interest. The general conditions under which statistical mechanics may describe the cosmological many-body problem are closely related to those for the applicability of thermodynamics described in detail previously by Saslaw and Hamilton. The statistical mechanics of N-body system is based on the N-body Hamiltonian. From this the partition function is formed as a function of an N-dimensional integral that incorporates the effects of gravitational interaction among all particles. The analytical expression for the grand canonical partition functions of point mass and of extended structures ( e.g. galaxies with halos ) are derived. From the partition function the thermodynamic properties and distribution functions of galaxies are derived for both point mass system and extended structures. The results agree very well with the N-body simulation analyses and observed spatial galaxy distribution. Further the irreducible triplet contribution to galaxy clustering in the cosmological many - body problem is evaluated.

ASI 2016 – Abstract Book 30

ASI-2016 Parallel Session - Thursday, 12 May, 2016

Time: 11:30 - 13:00 Venue: Ibn Khaldoon Auditorium

Extragalactic Astronomy–III [Chairperson: Pushpa Khare]

ASI2016_836 R. Srianand 11:30-12:00 Invited

On the star formation in high-z DLAs

High redshift Damped Lyman alpha systems(DLAs) detected in the spectrum of distant QSOs contain most of the HI in the universe. Measuring the in situ star formation associated with these absorbers are very important for understanding the star formation rate density of the universe and its redshift evolution. The in situ star formation can be measure by directly detecting host galaxies of these absorbers or by carefully studying physical conditions in these absorbers. In this presentation I will summarise the results based on both these approaches and summarise our present understanding of high-z DLAs and their implications to galaxy formation in the early universe.

ASI2016_838 J. N. H. S. Aditya 12:00-12:15 Oral

Nissim Kanekar National Centre for Radio Astrophysics, TIFR

Cold Gas in High Redshift Galaxies

We have conducted a survey using Giant Metrewave Radio Telescope to search for “associated” redshifted HI 21 cm absorption from 76 active galactic nuclei (AGNs), selected from the Caltech-Jodrell Bank Flat-spectrum (CJF) sample. Out of 63 sources which have usable data 17 sources are at 0 < z < 0.5, 39 are at 1.1 < z < 1.5 and 7 are at z ~ 3.5. We have obtained detections of HI 21 cm absorption in 4 sources, out of which one is a tentative detection towards TXS 0604+728 at z = 3.53. If confirmed, this would be the highest redshift at which HI 21 cm absorption has been detected till date. Including 29 CJF sources with searches for redshifted HI 21 cm absorption in the literature, mostly at z < 1, we construct a sample of 92 uniformly-selected flat- spectrum sources. A Peto-Prentice two-sample test for censored data finds (at ≈ 3σ significance) that the strength of HI 21 cm absorption is weaker in the high-z sample than in the low-z sample; this is the first statistically significant evidence for redshift evolution in the strength of HI 21 cm absorption in a uniformly selected AGN sample (ref Aditya et al.2015, MNRAS). However, the two-sample test also finds that the HI 21 cm absorption strength is higher in AGNs with low ultraviolet or radio luminosities, at ≈ 3.4σ significance. The fact that the higher-luminosity AGNs of the sample typically lie at high redshifts implies that it is currently not possible to break the degeneracy between AGN luminosity and redshift evolution as the primary cause of the low HI 21 cm opacities in high-redshift, high-luminosity active galactic nuclei. We further plan to observe 36 sources of the CJF sample in 0.4 < z < 1.0, which have high AGN luminosities, using GBT (~21 hrs allocated), to break this degeneracy. Additionally, we have observed 13 Gigahertz peaked spectrum (GPS) sources, 9 at z < 0.4 and 4 at 1.1 < z < 1.5, using GMRT, to test if the same results are applicable in a total sample of 58 GPS sources (remaining 45 sources are selected from literature). The data analysis of these sources is in progress. ASI 2016 – Abstract Book 31

ASI2016_871 Charles Jose 12:15-12:30 Oral

Prof. Kandaswamy Subramanian, IUCAA, Pune Prof. Raghunathan Srianad, IUCAA, Pune Dr. Cedric Lacey, ICC, Durham Prof. Carlton Baugh, ICC, Durham

Non-linear clustering of high redshift galaxies

We investigate the spatial clustering of dark matter halos, collapsing from 1−4 σ fluctuations, in the redshift range 0−5 using N-body simulations. The halo bias of high redshift halos (z≥2) is found to be strongly non- linear and scale-dependent on quasi-linear scales that are larger than their virial radii (0.5−10 Mpc/h). However, at lower redshifts, the scale-dependence of non-linear bias is weaker and and is of the order of a few percent on quasi-linear scales at z∼0. We find that the redshift evolution of the scale dependent bias of dark matter halos can be expressed as a function of four physical parameters: the peak height of halos, the non- linear matter correlation function at the scale of interest, an effective power law index of the rms linear density fluctuations and the matter density of the universe at the given redshift. This suggests that the scale- dependence of halo bias is not a universal function of the dark matter power spectrum, which is commonly assumed. We provide a fitting function for the scale dependent halo bias as a function of these four parameters. Our fit reproduces the simulation results to an accuracy of better than 4% over the redshift range 0≤z≤5. We also extend our model by expressing the non-linear bias as a function of the linear matter correlation function. In particular we find that the non-linear bias significantly reshapes the correlation functions of high reshift LBGs on scales 10 ≤ θ ≤ 100 arcsec, providing remarkable agreement with observed data. We expect our results can be applied to the clustering of halos at any redshift, including those hosting early generations of stars or galaxies before reionizatio

ASI 2016 – Abstract Book 32

ASI2016_473 Katherine Rawlins 12:30-12:45 Oral

Gargi Shaw (UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Santa Cruz East, Mumbai 400 098, India), Raghunathan Srianand (Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411 007, India), Hadi Rahmani (Aix Marseille Universite, CNRS, Laboratoire d‟Astrophysique de Marseille UMR 7326, 13388, Marseille, France) & Rajeshwari Dutta (Inter-University Centre for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411 007, India) Multi-component $H_{2}$ absorption in a damped Lyman-$\alpha$ absorber at $z_{abs}$ = 2.054 - spectroscopic analysis & simulation Damped Lyman-$\alpha$ absorbers (DLAs) are quasar absorption line systems with very high column densities of neutral hydrogen, N(H I) ≥ $10^{20.3}$ $cm^{-2}$. They are inter-galactic clouds associated with star formation and are important to our understanding of galaxy formation and evolution. However, despite the large values of N(H I), $H_{2}$ is detected in only 10-15% of all DLAs. We perform detailed spectroscopic analysis & simulation of an $H_{2}$-bearing DLA at $z_{abs}$ = 2.054 towards the quasar J2340-0053. This system is spread over 14 components. Out of these, 7 components show $H_{2}$ absorption. Such multi- component molecular absorption features are rare, making this an interesting system to study. The spectrum was obtained using the Ultraviolet & Visual Echelle Spectrograph at the Very Large Telescope, Chile. We derive column densities for the various observed species - Al III, C II*, Al II, Si II, S II, Fe II, Ni II, Zn II, C I, Mg I and $H_{2}$ - using the Voigt profile fitting package VPFIT (http://www.ast.cam.ac.uk/~rfc/vpfit.html). $H_{2}$ is detected in the lowest six rotational levels of the ground vibrational state. We get a rough estimate of metallicity, dust-to-gas ratio, and the possible range of gas temperature and hydrogen density from the observed column densities. The spectral synthesis code CLOUDY (http://www.nublado.org/) is then used to simulate the prevailing physical conditions in the $H_{2}$ components individually. These well-constrained models for the $H_{2}$ components help us to deduce the physical structure of this DLA cloud accurately.

ASI 2016 – Abstract Book 33

ASI2016_481 Sonali Sachdeva 12:45-13:00 Oral

Dimitri Gadotti, ESO, Kanak Saha, IUCAA, H.P. Singh, University of Delhi

Evolution of disc galaxies for the past 8 Gyrs

Establishing relative role of internally and externally driven mechanisms responsible for disc and bulge growth is essential to understand the evolution of disc galaxies. In this context, we have studied the physical properties of disc galaxies without classical bulges in comparison to those with classical bulges since z~1. We find that accretion of external material has been a dominant mode of galaxy growth, where the circum-galactic environment plays a significant role.

ASI2016_406 Sandeep Rana 13:00-13:15 Oral

Dr. J.S Bagla, Dr. Jayram Chengalur

HI intensity mapping, co-adding and cross-correlation

We study the distribution of HI at low redshifts using the ALFALFA and SDSS surveys. We use these to understand the sensitivity required for observing the distribution of HI at intermediate redshifts using three different approaches: HI intensity mapping, cross-correlation, and, co-adding of signal. We also comment on information that we can extract in each of these modes.

ASI 2016 – Abstract Book 34

ASI-2016 Parallel Session - Thursday, 12 May, 2016

Time: 11:30 - 13:00 Venue: Biotechnology Auditorium

Instrumentation and Techniques–II [Chairperson: T. P. Prabhu]

ASI2016_789 Maheswar Gopinathan 11:30 – 12:00 Invited

Brijesh Kumar, Amitesh Omar ARIES

3.6m Devasthal Optical Telescope (DOT): Commissioning and early science

The Devasthal Optical Telescope (DOT) is a 3.6-meter astronomical research telescope capable of making observations at optical and near-IR wavelengths. The telescope is a two-mirror Ritchey-Chretien system with f/9 configuration and an alt-azimuth mount. The telescope will be able to support instruments at the main Cassegrain port and two side ports. An uncorrected field-of-view of 10 arc-minitue will be available at the main Cassegrain port. In this talk I will be presenting results of the commissioning tests and possible early science observations.

ASI2016_765 Sunetra Giridhar 12:00-12:30 Invited

Sunetra Giridhar, T.Sivarani et al. Indian Institute of Astrophysics, Bangalore

HESP: an echelle spectrograph for 2m HCT

A new echelle spectrograph has been commissioned for the 2m Himalayan Chandra Telescope (HCT) at Indian Astronomical Observatory(IAO), Hanle in 2015. The Hanle Echelle Spectrograph (HESP) has been designed as facility instrument to support a large number of astronomical programs requiring high spectral resolution. The key features of the spectrograph are (i) a large continuous spectral coverage (350-1000nm) in a CCD single frame, (ii) High throughput (22\%) at the 500nm (iii) very low scattered light (less than 1.5\% (iv) double fiber for simultaneously recording star+sky or star+arc spectra with inter-order spacing larger than 30 pixels (v) resolution of 30,000 in unsliced and 60,000 in sliced mode (vi) high mechanical stability. In this article we present the results from the first light and commissioning run. The preliminary results indicate that the instrument meets the technical specifications and hence can support the science goals such as astrochemistry, exoplanets, galactic evolution and study of late stage of stellar evolution.

ASI 2016 – Abstract Book 35

ASI2016_428 Prasanna Deshmukh 12:30-12:45 Oral

Prasanna Deshmukh, Padmakar Parihar

Simulator for Primary Mirror Control System of Segmented Mirror Telescope

Segmented mirror technology is slowly becoming a natural choice for new generation telescopes of mid to large sizes. The challenge with the segmented primary mirror telescope (SMT) is to maintain the alignment of mirror segments against gravity, thermal and wind induced disturbances. In order to accomplish this, each mirror segment is actively controlled using three actuators per segment and two edge sensors along each inter- segment gap. The conversion of sensor positions to required displacement in actuator space is carried out by using primary mirror control system (M1CS), which utilizes an interaction control matrix. As telescope size increases, control of segmented mirror telescope becomes more and more challenging due to its complexity and presence of high order system. Another factor which needs to be carefully studied is the effect of sensor/actuator noise. In the M1CS control, propagation of uncorrelated sensor noise gets reflected as different modes (surface distortion) in the primary mirror. We have developed a generic M1CS simulator for SMT using Matlab & Simulink. Our simulator, can handle, variable sizes of mirror segments and number of segment rings, different geometrical configurations of edge sensor and actuators, different noises sources, disturbances etc. Simulator generates a C code which can directly be implemented in M1CS processor. We have also developed a tool which interfaces simulator to ZEMAX for further optical analysis and performance evaluations. In this paper we will present different aspects of the M1CS Simulator for SMT along with its application to the Prototype Segmented Mirror Telescope (PSMT) which is a seven segment test bed telescope under design and development at Indian Institute of Astrophysics.

ASI2016_554 Vineeth Valsan 12:45-13:00 Oral

S. Sriram: IIA; N. K. Mishra: IIA; G. C. Anupama: IIA; J. P. Lancelot: IIA;

Development of Stressed Mirror Polishing Technology

Stressed Mirror Polishing (SMP) is a fast and low cost method to polish large off-axis aspherical mirrors. The mirror blank is warped by the application of moments and shear forces around the periphery of the mirror blank. There will be a Whiffletree system supporting the mirror blank from below. After the application of moments, the top-surface of the blank attains the profile, which will be the exact opposite to the required profile. This surface undergoes polishing to acquire a spherical profile, following which, the stresses are removed and the mirror deforms itself to achieve the required surface profile. There are four components of SMP. 1. Stressing forces: Applied through levers bonded around the outer periphery of the of the mirror blank; 2. Self adjusting back support to achieve Zero-G condition; 3. Lateral constrain: The segment must be supported against lateral (side) loads that would tend to shear the part radially off the fixture and against clocking (rotation) on the fixture; 4. Axial constrain: In order to limit the axial movement of the mirror blank. This work deals with the design of all these components. Also discussed are the methods for calculating the amount of stress that has to be applied to the levers, modelling the support points from below the mirror blank and also the axial and lateral constraints.

ASI 2016 – Abstract Book 36

ASI-2016 Parallel Session - Thursday, 12 May, 2016

Time:14:30-16:00 Venue: Ibn Khaldoon Auditorium

General Relativity and Cosmology-II [Chairperson: Jasjeet Bagla]

ASI2016_761 K. Subramanian 14:30–15:00 Invited

Kandaswamy Subramanian (IUCAA)

Origin of Cosmological magnetic fields: Primordial AND dynamos?

Inflation provides a natural setting for the generation of coherent primordial magnetic fields. However, one needs to overcome several challenges to do with the predicted strength of the field and the strong coupling problem. We discuss possible resolutions. Even if the origin were primordial, dynamos are essential for maintaining the field. We show that this can occur easily if the field were strong and helical. For non-helical or weak fields conventional dynamos are required. We review recent work which shows that fluctuation dynamos could indeed provide the degree of coherence needed for cluster fields, and that mean-field dynamos could indeed generate large-scale fields on saturation, even in the presence of strongly growing fluctuations!

ASI2016_594 Shishir Sankhyayan 15:05–15:15 Oral

Joydeep Bagchi (IUCAA, Pune)

Large Scale Structures and Clusters-Voids Cross-correlation

We report a high concentration of 43 clusters (mass >= 10^14 M_sun each) at z ~ 0.28. We call this concentration - "Saraswati Supercluster". The comoving extent of these 43 clusters is ~ 190 Mpc. It seems, though work is still in progress, that this high concentration of clusters is unusual in LCDM model. It is observed that high concentration of clusters are surrounded by voids. Voids surround the Saraswati Supercluster as well. The dark energy density in voids is higher than the average dark energy density of the Universe. This means that void regions must expand at higher rate than the mean expansion rate and this might be helping the clustering of dark matter on the edges of voids. In order to understand the role of dark energy helping in structure formation (atleast on the edges of the voids), we calculate the clusters-voids cross- correlation and see how this changes for very high concentration of clusters, like Sararwati.

ASI 2016 – Abstract Book 37

ASI2016_883 Rajesh Mondal 15:15–15:30 Oral

Rajesh Mondal, Department of Physics, Indian Institute of Technology Kharagpur

Statistics of the epoch of reionization 21-cm signal : Power spectrum error-covariance

The non-Gaussian nature of the epoch of reionization (EoR) 21-cm signal has a significant impact on the error variance of its power spectrum P(k). We have used a large ensemble of seminumerical simulations and an analytical model to estimate the effect of this non-Gaussianity on the entire error-covariance matrix C_ij . Our analytical model shows that C_ij has contributions from two sources. One is the usual variance for a Gaussian random field which scales inversely of the number of modes that goes into the estimation of P(k). The other is the trispectrum of the signal. Using the simulated 21-cm Signal Ensemble, an ensemble of the Randomized Signal and Ensembles of Gaussian Random Ensembles we have quantified the effect of the trispectrum on the error variance C_ii. We find that its relative contribution is comparable to or larger than that of the Gaussian term for the k range 0.3≤k≤1.0 Mpc^−1 , and can be even ∼200 times larger at k ∼ 5 Mpc^−1 . We also establish that the off-diagonal terms of C_ij have statistically significant non-zero values which arise purely from the trispectrum. This further signifies that the error in different k modes are not independent. We find a strong correlation between the errors at large k values (≥0.5 Mpc^−1 ), and a weak correlation between the smallest and largest k values. There is also a small anticorrelation between the errors in the smallest and intermediate k values. These results are relevant for the k range that will be probed by the current and upcoming EoR 21-cm experiments.

ASI2016_556 Asif Iqbal Ahangar 15:30 – 15.45 Oral

Asif Iqbal^1, Subhabrata Majumdar^2, Biman B. Nath^3 and Manzoor A. Malik^1 ^1 Department of Physics, University of Kashmir, Hazratbal, Srinagar, J&K, 190001, India ^2 Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai, 400005, India ^3 Raman Research Institute, Sadashiva Nagar, Banglore, 560080, India

Entropy excess and energy deposition profile in galaxy clusters up to virial radius

Recent studies have revealed that non-gravitational processes play important role in modifying the thermodynamic properties of the intracluster medium (ICM). It has also been observed that there is entropy enhancement in galaxy clusters which is believed to be a result of the non-gravitational feedback from active galactic nuclei, radiative cooling, supernovae etc. Here, we study the entropy and energy deposition profiles in galaxy clusters due to the non-gravitational processes by comparing the observed entropy profiles to the baseline simulated entropy profiles without feedback from both adaptive mesh refinement (AMR) and smoothed particle hydrodynamic (SPH) up to the virial radius. We find that energy per particle to be around 0.6-1.6 kev up to r500 in galaxy clusters. Moreover, in the outer regions which directly probe the feedback energy duo pre-heating era, we show that any significant preheating is ruled out.

ASI 2016 – Abstract Book 38

ASI2016_590 Bidisha Bandyopadhyay 15:45 – 16.00 Oral

Dominik R. G. Schleicher, Departamento de Astronom\'ia, Facultad Ciencias F\'isicas y Matemt\'icas, Universidad de Concepci\'on, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C, Concepci\'on, Chile

Can Annihilating Clumped Dark Matter lead to Helium Reionization?

Helium reionization is an important phenomenon during the course of the thermal evolution of the IGM. The mean free path of photons above 54.4 eV are affected by this process. Helium reionization is mostly driven by energetic photons from quasars at z<6. However, here we explore a different mechanism through which the reionization is achieved. In this work we have investigated how annihilation of dark matter inside halos during structure formation can contribute to reionization of helium at z>6. An important factor that influences the extent to which annihilation of dark matter is the degree of clumping. We study the effect of the dark matter clumping factor (which depends on the density profiles) in enhancing the annihilation rate at late times. We find that the clumping leads to an additional fraction of ionized helium as compared to the standard model.

ASI 2016 – Abstract Book 39

ASI-2016 Parallel Session - Thursday, 12 May, 2016

Time: 14:30 - 16:00 Venue: EMMRC Auditorium

Stars, The Milky Way Galaxy and its Neighbours–III [Chairperson: H.P. Singh]

ASI2016_568 Sharanya Sur 14:30-15:00 Invited

Evan Scannapieco (Arizona State University) Eve C. Ostriker (Princeton University)

Galaxy outflows without supernovae

High surface density, rapidly star-forming galaxies are observed to have ≈ 50 - 100 km/s line-of-sight velocity dispersions, which are much higher than expected from supernova driving alone. I will describe three- dimensional interstellar medium simulations that explore the impact of such high velocity dispersions, which arise from gravitational instabilities. The motions lead to strong global outflows, triggered by a thermal runaway caused by turbulent heating coupled with the inefficient cooling of > 105 K material. Our results suggests that in strongly, self-gravitating disks, outflows may be enhanced by, but need not be caused by, energy input from supernovae.

ASI2016_699 Naveen Yadav 15:00-15:15 Oral

Naveen Yadav, IISc Prateek Sharma, IISc Biman Nath, RRI Dipanjan Mukherjee, ANU

Dynamics of Supernova Driven Supershells we explore formation of superbubbles through energy deposition by multiple supernovae in the surrounding medium. We use total energy conserving 3-D hydrodynamic simulations to study the dynamics and energetics of superbubble formation. We study the scenario in which all the supernovae are correlated in space and time, occurring within a cluster of finite radius and lifetime. While isolated supernovae fizzle out completely by $\sim 1$ Myr, for a realistic cluster size it is likely that subsequent supernovae go off within the bubble and sustain the shock till the cluster lifetime, $\sim 30$ Myr, similar to the galactic dynamical timescale. We scan the parameter space of ISM density ($n_{\rm g}$), number of supernovae ($N_{\rm OB}$), and star cluster radius ($r_{\rm cl}$) to study the conditions for the formation of an over-pressured (super)bubble. For realistic cluster sizes, we find that the bubble remains over-pressured only if, for a given $n_{\rm g}$, $N_{\rm OB}$ is sufficiently large. While most of the input energy is still lost radiatively, superbubbles can retain up to $\sim 30\%$ of the input energy for several 10s of Myr. We find that radiative losses are enhanced (by $\approx 2$) in realistic 3-D simulations as compared to 1-D because of crinkling of radiative boundary layers. We compare the radius and velocity evolution of our shell with classic models and observations. We also confirm that a sufficiently large ($\gtrsim 10^4$) number of supernovae are required to go off in order to create a steady wind within the superbubble. We also briefly assess the influence of ISM density fluctuations on our results.

ASI 2016 – Abstract Book 40

ASI2016_527 Jayant Murthy 15:15-15:30 Oral

None

Modeling the diffuse ultraviolet background

Although an important part of our Galaxy, interstellar dust is difficult to characterize. Historically, most of our information about dust has come from observations of extinction curves against background stars but these are limited to those directions where there are suitable stars. Infrared observations of the thermal emission from dust heated by the interstellar radiation field fills the sky and has yielded considerable information about the properties and the distribution of the dust. Ultraviolet observations of the scattered light from the dust have been difficult and sparse until the launch of the GALEX mission. I will discuss my extraction of this diffuse light from the GALEX data and what it tells us about the properties of interstellar dust. My primary focus will be on the modeling I am now doing and on its successes and deficiencies.

ASI2016_790 Smitha Subramanian 15:30-15:45 Oral

Richard de Grijs Kavli Institute for Astronomy & Astrophysics, Peking University, Department of Astronomy, Peking University, Beijing China) Andres Piatti (Observatorio Astronómico, Universidad Nacional de Córdoba,, Argentina) Leo Girardi (Osservatorio Astronomico di Padova - INAF, Vicolo dell'Osservatorio 5Padova, Italy) Maria Rosa Cioni (University of Hertfordshire, Physics Astronomy and Mathematics, UK; Leibnitz-Institut für Astrophysik Potsdam, Germany) Jacco van Loon (Lennard-Jones Laboratories, Keele University, UK) Ningchen Sun (Kavli Institute for Astronomy & Astrophysics, Peking University, Department of Astronomy, Peking University, Beijing, China) Benjamin Tatton (Lennard-Jones Laboratories, Keele University, UK)

Signatures of a tidally stripped stellar population from the inner regions of the Small Magellanic Cloud

The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are satellite galaxies of the Milky Way and the closest pair of interacting galaxies. The signatures of their interactions are seen in neutral HI in the form of the so-called Magellanic Bridge(MB), Magellanic Stream and the leading arm. The Magellanic Bridge is mainly a gaseous feature connecting the two galaxies, with a small fraction of in situ formed young stars. The MB is believed to be composed of tidally stripped material from the SMC during its last encounter with the LMC, approximately 200-300 Myr ago. Although predicted by tidal models, the presence of a tidally stripped old/intermediate-age stellar population in the MB is not very evident. Some previous studies have found signatures of tidally stripped stars in the outer regions (at ~4 degrees from the centre) of the eastern SMC, which may be connected to the MB. We studied the magnitude distribution of the red clumps stars using deep,near-infrared Y- and Ks-band photometric data covering ~18 squaredegrees of the SMC, comprising the main body and the galaxy's eastern wing, based on observations obtained with the VISTA Survey of the Magellanic Clouds (VMC). From this analysis, we identified regions which show a foreground population (at ~10 kpc in front of the mainbody) in the form of a distance bimodality in the red clump distribution. The most likely explanation for the origin of this feature is tidal stripping from the SMC. The homogeneous and continuous VMC data traces this feature in the direction of the MB and,particularly, identifies (for the first time) the inner region (~2.5degrees from the centre) from where the signatures of interactions start becoming evident/detectable. This result has important implications for our understanding of the nature of the interaction and the physical properties of these galaxies.

ASI 2016 – Abstract Book 41

ASI2016_938 Samir Mandal 15:45-16:00 Oral

Samir Mandal IIST

Spectral properties of pair-plasma in disc-jet system around black hole

We calculate the thermal pair equilibrium solution in an accretion disc around black hole. We take into account different heating and cooling processes. We also study the radiation spectrum of the disc-jet system around black hole using the pair balance solutions and try to understand the spectral characteristic of pair production in an accretion disc.

ASI 2016 – Abstract Book 42

ASI-2016 Parallel Session - Thursday, 12 May, 2016

Time: 14:30 - 16:00 Venue: Biotechnology Auditorium

Sun and Solar System–II [Chairperson: Divya Oberoi]

ASI2016_664 Piyali Chatterjee 14:30-15:00 Invited

Viggo Hansteen Mats Carlsson

Mystery of repeatedly flaring delta sunspots

Delta sunpots - special kind of sunspots seen on the solar surface with North-South polarity regions appearing very close to each other - are known to flare repeatedly and are responsible for about 95% of the X-ray flares we observe on the Sun. Most energetic of these X-ray flares if Earth-directed have tremendous potential to affect our antropological activities that we take for granted e.g., electricity supply, GPs, radio communication, air flights etc. Here we present results from a computer simulation showing how, starting from a very simple initial condition, the interaction between solar magnetic fields and turbulent convection produces a pair of opposite polarity sunspots which collide and merge to form a delta sunspot. This delta-sunspot produces flares with energies comparable to those typically observed on our Sun during the simulation spanning four solar hours. The novelty of this work is that it captures various aspects of flare observations like the formation and eruption of hot and bright sigmoid-shaped structures, cool and dark filaments, as well as bipolar jets and their temporal correlation with the epoch of magnetic energy release.

ASI2016_842 Sreejith Padinhatteeri 15:00-15:15 Oral

Sreejith Padinhatteeri [1], Jack Cahalane[2], Paul A. Higgins [2], D. Shaun Bloomfield [2] and Peter T. Gallagher [2] [1] Manipal Center for Natural Sciences, Manipal University, Maipal, India [2] Trinity College Dublin, Dublin, Ireland.

Delta-sunspot groups and Solar Flares

Sunspot groups that contain opposite-polarity umbrae surrounded by a common penumbra are known as delta spots in the modified Mount Wilson classification scheme. These magnetically complex sunspot groups are associated with many major solar flares, so the formation of a delta spot can be a precursor of an active region's potential for major flaring. We have developed an algorithm (SMART Delta Finder; SMART-DF) to automatically detect delta spots from simultaneous continuum intensity and magnetogram observations. This tool can be used to analyse archive data as well as working with near-realtime observations. We have used this tool to analyse the past 15 years of data and investigate the correlation between solar flares and delta spots. In this talk, we present this new software package and results from the statistical study of delta spots and solar flares.

ASI 2016 – Abstract Book 43

ASI2016_810 Suruchi Goel 15:15-15:30 Oral

Sami K. Solanki (MPS, Germany), Natalie A. Krivova (MPS, Germany), Shibu K. Mathew (USO, PRL, India)

The statistical study of global properties of sunspots in SoHO/MDI continuum images over solar cycle 23.

A better understanding of inter-dependency of various sunspot parameters such as magnetic field, intensity, temperature, size etc., and also their variation with strength of solar activity cycle is important to understand the magneto-convection process involved in sunspot formation and evolution and hence useful to develop a consistent sunspot model. We have investigated global sunspot properties using parameters of sunspots identified from stray-light-corrected continuum images from SoHO/MDI spanning from years 1996 to 2011. We find that the non-linear relation between umbral core intensity and sunspot size is best represented by an exponential function. This non-linear relation shows that the umbrae of large sunspots are relatively darker and cooler than small spots, however it reaches an asymptotic value at 600MSH. For the first time we have also observed that the core intensity depends on shape of umbrae, i.e., circular umbrae are darker compared to the elongated ones. The core intensity also shows small variation with limb position; it increases slightly towards the limb. From our sunspots sampled from complete solar cycle 23 and the rising phase of cycle 24, we did not find any solar-cycle variation in umbral core intensity. Similar to the core intensity the umbral mean intensity decreases with the sunspot size, their relation is well represented by a quadratic function. The penumbra to umbra area ratio has slight dependence on the sunspot area; larger sunspots have relatively higher ratios. Leading and following sunspots usually have different morphological features, however in this study we did not observe significant differences in their core intensity and penumbra-umbra area ratio relation with sunspot area.

ASI2016_538 Vaibhav Pant 15:30-15:45 Oral

1.Sudarshan Sarnathan, Indian Institute of Astrophysics 2. Ankur Chauhan, Hansra College, Delhi University 3. Dipankar Banerjee Indian Institute of Astrophysics

Kinematics of fast and slow CMEs

We report the kinematics of slow and fast CMEs during cycle 23 and 24. We classify CMEs as slow and fast based on the speed of propagation. We find that slow and fast CMEs behave quiet differently in cycle 24 as compared to cycle 23. We also attempted to study the evolution of CME width with time and estimated the time and distance of width saturation. It has an interesting implications on the behavior of heliospheric magnetic field.

ASI 2016 – Abstract Book 44

ASI2016_651 Tanmoy Samanta 15:45-16:00 Oral

Tanmoy Samanta, Vaibhav pant and Dipankar Banerjee

Response of chromospheric jets in the corona

The solar chromosphere and transition region plays an important role in understanding the interaction between the relatively cool photospheric plasma and the hot multi-million degree corona. It is only beginning to be understood where and how the required energy is generated, transported and dissipated. It appears that the chromosphere and transition region plays a key role in the process. Dynamic jets as observed with high resolution Interface Region Imaging Spectrograph (IRIS) are currently being studied. We found that these jets are associated with coronal dynamics. This association between jets seen in the chromosphere and material heated to millions degree temperatures seen in the corona, suggests that they play an important role in supplying and also heating the plasma to maintain the corona. Our observations indicates that a common process which generates small-scale jets also generates propagating intensity perturbations in the corona. It is most likely that the observed PDs are magneto-acoustic waves which propagate to higher heights while the cool jet material falls back.

ASI 2016 – Abstract Book 45

Friday, May 13, 2016

ASI-2016 Plenary Session

Multi-messenger Astronomy [Chairperson: Ram Sagar]

Time: 9.30 am - 11.30 am Venue: Convocation Complex

ASI2016_797 Varun Bhalerao 9.30 am - 10.00 am Plenary

Einstein's messengers: gravitational wave sources and their electromagnetic counterparts

An advanced network of gravitational wave detectors are expected to obtain the first direct detections of gravitational waves within the next few years, opening up a exciting new window in multi-messenger astrophysics. The proposed LIGO-India interferometer will join this network as we approach the era of gravitational wave astronomy. While the interferometric detectors can yield certain parameters of gravitational wave sources, complementary studies in electromagnetic wavelengths are crucial for a complete astrophysical understanding. In this talk, I will talk about gravitational wave sources, their electromagnetic counterparts, and what we can learn from them. I will highlight why India forms a key node in this global effort, and discuss prospects of optical, radio and X-ray follow-up from India.

ASI2016_631 Amol Dighe 10.00 am - 10.30 m Plenary

Pauli's messengers: Looking at the sky in neutrinos

Neutrinos with energies ranging from meV to EeV pervade the universe, and act as messengers that bring signals of astrophysical events even from places from where light cannot reach us. Their presence and their mass has influenced cosmology, and they continue to play crucial roles in astrophysical phenomena like core collapse supernovae. This talk will briefly describe how future observations of neutrinos will enrich our knowledge of particle physics, astrophysics, and cosmology.

ASI 2016 – Abstract Book 46

ASI2016_704 Kuntal Mishra 10.30 am - 11.00 am Plenary

Optical Transients

Since the last decade new optical survey telescopes equipped with large format detectors have revolutionized the field of transient astronomy. This has resulted in discovery of slow to rapid transients opening up a wide range of astrophysical processes. In this talk I will discuss about the extragalactic transients (such as Gamma Ray Burst Afterglows and Supernovae) that mark the end stages of stellar evolution and are a result of catastrophic explosions. I will present a comprehensive data/modeling of a few of these transients, by combining the optical data with other wavelengths, which is used to explore the various physical processes involved in stellar explosions and to derive the physical parameters.

ASI 2016 – Abstract Book 47

ASI 2016 Thesis Presentations

Time: 11.30 am - 13.30 am

ASI2016_587 S. Rathna Kumar Thesis

Thesis Advisor: C. S. Stalin (Indian Institute of Astrophysics)

Determination of $H_0$ through monitoring of gravitationally lensed quasars

The Hubble constant at the present epoch ($H_0$), the current expansion rate of the Universe, is an important cosmological parameter on which all extragalactic distances and the age of the universe depend. Multiple approaches are needed to measure its value in order to be able to identify and eliminate unknown systematics present in any one approach. Strong gravitational lensing offers one method, which is based on measuring the differences in light travel-time between the multiple images of a variable background source which is strongly lensed by a galaxy which lies in close proximity to its line of sight. The time delays between the images of the background source can be measured by monitoring their brightness variations and comparing the variability features in their light curves. Converting measured time delays into $H_0$ also requires knowledge of the mass structure of the lensing galaxy as well as the source and lens redshifts. A sample of lensed quasars were photometrically monitored using the 2-m Himalayan Chandra Telescope as part of the COSMOGRAIL campaign, which aims to measure the time delays of most known lensed quasars in both hemispheres, using a network of medium-size optical telescopes. Since the angular separations between the images of lensed quasars are comparable to typical seeing values obtained in ground based telescopes, we made use of MCS deconvolution algorithm to carry out accurate photometry of the individual quasar images. Measurement of time delays between the light curves of quasar images is non-trivial due to the irregular temporal sampling of the light curves arising from telescope scheduling and weather constraints, the presence of seasonal gaps in the light curves spanning several months during non-visibility periods of the object, and the presence of uncorrelated brightness variations in the light curves that could arise due to microlensing of the quasar macro-images by stars in the lensing galaxy. Taking all these factors into account, we devised a technique for time delay measurement called “difference-smoothing”. The thesis presented the measurements of time delays of two doubly lensed quasars for the first time. We also analyzed the publicly available light curves of the 24 lensed quasars for which time delays had been reported in the literature in a homogeneous manner using the difference-smoothing technique and identified those systems for which the light curves were of sufficiently good quality to enable reliable measurement of time delays. Of those systems, we further selected a sub-sample for pixellated lens modeling using the publicly available PixeLens code to infer the value of $H_0$.

ASI 2016 – Abstract Book 48

ASI2016_686 Subramania Athiray Thesis

P. S. Athiray, Manipal Centre for Natural Sciences

Study of lunar surface chemistry using Swept Charge Devices

Studying the surface chemical composition of the Moon is of prime scientific importance as it preserves record of early geological history of the solar system. This thesis investigate the chemical composition of lunar surface through X-ray Fluorescence (XRF) technique, utilizing data from the Chandrayaan-1 X-ray Spectrometer (C1XS) on board Chandrayaan-1. C1XS experiment was designed to map the distribution of abundances of major rock-forming elements viz., Mg, Al, Si, Ca, Ti and Fe on the lunar surface. A detailed summary of entire C1XS observations, data selection methods and spectral analysis procedures are explained. This thesis demonstrate the first direct detection and quantification of moderately volatile element Sodium (Na) on the lunar surface. An independent XRF inversion algorithm 'x2abundance', that can convert XRF line intensities to elemental abundances is detailed. Validation of 'x2abundance' using laboratory XRF experiments and GEANT4 simulations with metal alloys and lunar analog rocks are explained in detail. Lunar surface elemental abundances are determined for the C1XS-observed regions using the inversion algorithm. New insights from C1XS results and its scientific significance on lunar surface studies are presented. The need for an improved global surface elemental mapping of the Moon and the development of Chandrayaan-2 Large Area Soft x-ray Spectrometer (CLASS) on board the upcoming Chandrayaan-2 mission have also been discussed. As the C1XS and CLASS experiments employ Swept Charge Devices (SCD) as X-ray detectors, a charge transport model is developed to better understand and predict the spectral redistribution function of SCD. Algorithm development, implementation and successful validation with C1XS ground calibration data are described. This Monte Carlo simulation will be quite useful during the calibration of X-ray detectors for the CLASS instrument. In the end, new developments with a few X-ray instrumental design aspects which can potentially improve surface investigation of Moon/airless planetary bodies in X-rays are discussed.

ASI 2016 – Abstract Book 49

ASI2016_543 Samyaday Choudhury Thesis

Study of evolved stellar populations in the Magellanic Clouds

The Magellanic Clouds (MCs), comprising of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are two nearby (~50 kpc), interacting galaxies to our Milky Way. In my thesis I have studied the sparse star clusters and metallicity distribution for one of the component of the MCs, the LMC. The study of sparse star clusters in the LMC is important in order to understand the cluster formation history of the LMC. The study aims to increase our understanding of sparse star clusters in the LMC, using deep Washington photometric data of 45 star clusters obtained from 4-m Blanco Telescope, CTIO. A systematic study was performed to estimate their parameters (radius, reddening, and age) using the main-sequence turn-off, as well as the evolved portion of the color- magnitude diagram (CMD). The basic parameters were estimated for 33 clusters, out of which 23 are identified as single clusters and 10 are found to be members of double clusters. The other 12 clusters are classified as possible clusters/asterisms. The sizes (~2-10 pc) and masses (~a few 100 - 1000 Msun) of these 45 inconspicuous clusters emphasises that the LMC has a significant population of clusters, which are similar to the open clusters in our Galaxy. To understand the metallicity distribution and gradient of the LMC, we estimated a metallicity map using the red giant branch (RGB) stars, from the Magellanic Cloud Photometric Survey (MCPS) and Optical Gravitational Lensing Experiment (OGLE III) photometric data. This is a first of its kind map of metallicity up to a radius of 4º - 5º , with good sampling of the bar region. The slope of the RGB is used as an indicator of the average metallicity of a subregion, and it is calibrated to metallicity using spectroscopic data for field and cluster red giants in selected subregions. The average metallicity of the LMC is found to be [Fe/H] = −0.37 dex (σ[Fe/H] = 0.12) from MCPS data, and [Fe/H] = −0.39 dex (σ[Fe/H] = 0.10) from OGLE III data. The bar is found to have an uniform and higher metallicity compared to the disk, and is indicative of an active bar in the past. Both the data sets suggest a shallow radial metallicity gradient up to a radius of 4 kpc (−0.049 ± 0.002 dex/kpc to −0.066 ± 0.006 dex/kpc ). This metallicity gradient of the LMC disk, though shallow resembles the gradient seen in spiral galaxies, and is also similar to that found in our Galaxy.

ASI 2016 – Abstract Book 50

ASI2016_458 K Sasikumar Raja Thesis

Supervisor: Dr. R. Ramesh, Indian Institute of Astrophysics, Bangalore, India

Radio Polarization Studies of the Solar Corona at Low-frequencies

The dedicated radio telescopes to continuously monitor the Sun and solar corona are limited. But such telescopes provide crucial information on coronal magnetic field strength, weak energy events, radio wave propagation in the corona, space weather and Earth's climate and different plasma parameters etc, which are further useful in understanding the unresolved mysteries of the solar corona. The electron density and hence the plasma frequency decreases in the solar corona with the radially outward increasing height. Also, different frequencies of observations correspond to different heights in the solar corona. Therefore, we designed and constructed a polarimeter, called Gauribidanur Radio Interference Polarimeter (GRIP) at Gauribidanur Radio Observatory, India, to monitor the corona in the Stokes I (total intensity) and Stokes V (circularly polarized intensity) modes which primarily operates in the bandwidth of 30-150 MHz. This operating bandwidth corresponds to the height approximately 1-2 R_sun above the photosphere. Note that the observations of the corona is difficult in this regime even with the `existing' space based coronagraphs because of the practical limitations. The GRIP consists of 40 log-periodic dipole antennas arranged in East-West direction in horizontal and vertical directions. After successful construction of the array, the observation of the Sun is being carrying out every day. In this talk, I will present the design and instrumental details of the GRIP and the observational results obtained with it. Some of them are observations of the weakest energy events in the corona (called picoflares) and their role in coronal heating, indirect methods of estimation of the magnetic field strength using the observations of quasi-periodic type III bursts in polarimetric mode, magnetic field strength associated with the coronal mass ejections (CMEs) and scattering studies using the Crab nebula occultation technique. I will conclude the talk by explaining the improved, newly designed/fabricated cross-polarized log-periodic dipole antenna system and the future scope.

ASI 2016 – Abstract Book 51

ASI2016_465 Drisya K Thesis

Prof. Aruna Goswami. Indian Institute of Astrophysics

Studies on Carbon-Enhanced Metal-Poor (CEMP) stars

Thesis Title: Studies on Carbon-Enhanced Metal-Poor (CEMP) stars Supervisor: Prof. Aruna Goswami Carbon-Enhanced Metal-poor (CEMP) stars are an important class of chemically peculiar stars; a large fraction of them show enhancement of carbon and heavy elements and are known to populate the halo of the Galaxy. They are population II objects formed from the ejecta of more massive population III stars. Hence chemical composition studies of CEMP stars are crucial to develop an understanding of the nature of the earliest stars formed in the universe, the nucleosynthesis events associated with them, as well as, to redefine the models of galaxy formation. Elements heavier than the iron peak are made via two principal processes: the rapid neutron-capture process (r-process) and the slow neutron-capture process (s-process). Among the CEMP stars, CEMP-s stars exhibit the presence of strongly enhanced s-process elements and CEMP-r stars are with strong enhancement of r-process elements. A number of CEMP stars, CEMP-r/s stars, exhibit enhancement of both r- and s-process elements. Insight into the astrophysical sites and the production mechanisms of neutron-capture elements can be obtained by studying chemical composition of stars that exhibit large enhancement of neutron-capture elements such as CEMP stars. According to certain spectral criteria carbon stars are again classified into different groups such as C-R, C-N, CH and C-J. Among these CH stars are most important because they are identified as the more metal-poor counter parts of CEMP-s stars and are believed to have a similar origin. The main goal of this thesis was to conduct detailed chemical composition study of a large sample of CEMP stars to understand the nucleosynthetic origin of the observed abundance patterns. We have carried out low-resolution spectroscopic analysis of a group of hundred and twelve CEMP stars to find potential CH (or CEMP-s) stars. High resolution spectroscopic analysis of a group of twenty two CH stars are also carried out to determine the detailed chemical abundances. A parametric model based study is conducted to understand the origin of the anomalous abundance patterns in them. From the high resolution spectroscopic analysis, we find eleven objects that exhibit enhancement of heavy elements also show radial velocity variations indicating their binary nature. Among these, seven objects show the characteristics of CEMP-s stars. The enhancement in heavy elements shown by the binaries are distinctly more compared to the other objects which do not belong to binary system. We have also noted an increasing trend of heavy element abundances with decreasing metallicity. In this talk, I will highlight some of these results and important conclusions drawn from this thesis work.

ASI 2016 – Abstract Book 52

ASI2016_591 Raja Bayanna Thesis

Shibu K. Mathew, Rohan E Louis, P.Venkatakrishnan, R. Sridharan, Brajesh Kumar, B. Ramyareddy

A Low-order Adaptive Optics System for Multi-Application Solar Telescope

Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope installed at the island site of Udaipur Solar Observatory (USO), India. Mean value of the Fried‟s parameter that characterises the atmospheric turbulence at this site is 4.5 cm. An Adaptive Optics (AO) system has been developed at USO for compensating image degradation, in order to achieve the telescope‟s diffraction limit. The main components of the system are (a) a stand-alone image stabilization system that compensates the global tilt of the distorted wavefront and (b) a Shack-Hartmann wavefront sensor along with a 37-Channel deformable mirror for sensing and correction of local tilts of the distorted wavefront. In this presentation, the AO system and the calibration of its various components will be described. We also present preliminary observations obtained with the MAST AO system.

ASI 2016 – Abstract Book 53

ASI2016_512 Archana Thesis

Dr. Maheswar G., ARIES, Nainital; Dr. Chang Won Lee, KASI, Republic of Korea; Prof. H. C. Bhatt, IIA, Bangalore

Investigation of galactic star forming regions and young stellar objects

The study of magnetic fields in molecular clouds formed in various environments have enormous potential towards understanding the underlying physics behind the role played by the magnetic fields in the formation of molecular clouds and the subsequent star formation. The closer and isolated molecular clouds provide the fascinating laboratories where the importance of magnetic fields can be explored towards ongoing activities like evolution of the cloud and star formation. The focus of this thesis is to explore the magnetic fields morphologies and strength in various environments of molecular clouds to understand the open issue of the role played by magnetic fields in interstellar medium (ISM). The regions where we have mapped the magnetic fields are broadly classified into the categories viz. triggered star forming and spontaneous star forming sites. In triggered star forming regions, we have chosen the multiple bright-rimmed clouds (BRCs) and cometary globules (CGs) associated to some HII regions surrounded by a high mass star in the center. The radiation driven implosion process explains the photoionization induced collapse of a dense, isolated cloud that is illuminated from one side by a source of ionizing radiation. In the presence of magnetic fields, the dynamical evolution of the globule and ionized gas streaming out of the globule surface get modified significantly depending on the strength and the orientation of the magnetic field. These HII regions are selected because of their structural simplicity and proximity to the sun. It has been widely accepted that the magnetic fields play an important role in the spontaneous star formation process. In a magnetic field dominated scenario for isolated low mass star formation, the cores are envisaged to gradually condense out of a magnetically sub- critical background cloud, through ambipolar diffusion. To understand the evolution of magnetic fields in the cores of different ages (ages deter- mined based onto the chemical evolution), we have studied the magnetic fields in a number of prestellar cores. Magnetic fields morphologies in some of the cores harboring very low luminosity objects (VeLLOs) have also been made in this thesis. These studies will help in understanding the standard models of low mass star formation and key role played by the magnetic fields in these processes. In order to understand the disk formation in the low mass stars, we have studied the magnetic field structure and following alignment/misalignment between the mean magnetic field direction and the rotation axis (the outflow axis is presumed to be the rotation axis of the core) in a core with a proto-brown dwarf candidate. Magnetic field strength have been estimated using the modified Chandrasekhar-Fermi (CF) relation. We have tried to constrain the standard models of low mass star formation through observations.

ASI 2016 – Abstract Book 54

ASI2016_681 V. Venkataraman Thesis

V.Venkataraman Physical Research Laboratory

Infrared investigations of circumstellar matter

Circumstellar matter enshrouds both the protostars which accrete from their surroundings as well as evolved stars which undergo significant mass loss, leading in both cases to an excess emission in the infrared (IR). The thesis presents infrared investigations of circumstellar matter around eruptive young pre-main sequence (PMS) stars and evolved low and intermediate mass stars. The eruptive events in PMS stars are believed to be caused by enhanced disk mass accretion. We report an unprecedented high cadence IR monitoring of V1647 Ori, an enigmatic eruptive variable star that attracted significant attention over the last decade. It experienced two episodes of outbursts during 2004 and 2008. The nature of the outburst and its similarity to the PMS eruptive events that are classified as FUors and EXors depending on the duration of the outburst makes it distinctive. The physical and circumstellar parameters obtained by modeling the spectral energy distribution (SED) during the outburst and quiescent phases showed marked differences. The disk mass and disk accretion rate during the outburst phase are significantly greater than those in the quiescent phase. The envelope mass and accretion rate are higher during quiescent phase. The second part of the thesis deals with the photometric and spectroscopic study of evolved stages of stars namely Asymptotic Giant Branch (AGB) and post-AGB (PAGB)/ Proto-planetary nebulae (PPNe) stages. The near-infrared (NIR) spectra of AGB stars showed CO vibration-rotation lines of first and second overtone bands. The equivalent width (EW) of the second overtone band of CO correlated with IR colors, suggesting a possible relationship with mass- loss processes. The NIR spectra of a sample of PAGB stars showed short-term spectral variability that is indicative of ongoing episodic mass loss. Cooler PAGB stars showed variation in CO first overtone lines, while hotter stars showed variability in HI lines. The mid-IR spectra of AGB stars obtained from the infrared space observatory (ISO) archives showed the presence of silicates either in absorption or emission. Also, the spectra showed the absence of polycyclic aromatic hydrocarbons (PAHs) in all our sample stars. The mid-IR spectra of PAGB/PPNe candidates obtained from the Spitzer data archive showed different spectral features that include emissions from PAHs. A trend of dependency was noticed between the EWs of various vibrational modes of PAHs and their photospheric temperature obtained by modeling the SED. The PAGB/PPNe mass loss rates obtained from the SED models are higher than the AGB mass loss rates. The significant difference between the AGB and PAGB/PPNe candidates lies in the SED of these sources where PAGB/PPNe sources have detached shells leading to a double humped SED while AGB candidates show a smooth SED due to the on-going mass loss. A few transition objects with low-excitation line emission of [NeII] were identified among PAGB/PPNe sample, which indicates their advanced stage of evolution. IR vibration modes of fullerenes (C60) were detected for the first time in the PAGB star IRAS 21546+4721 making it one of the very few evolved stars that showed the presence of fullerenes. Thesis supervisor: Prof. B.G.Anandarao

ASI 2016 – Abstract Book 55

ASI-2016 Poster Presentations

Sun and Solar System

SSS-1 ASI2016_383 Dipankar Banerjee Poster

Digitization team

Kodaikanal Digitized Archive and long term study of the Sun

The Sun has a magnetic field which oscillates with the 11yr sunspot cycle. We have direct systematic measurements of the Sun‟s magnetic field only from about the mid-1970s. There are, however, indirect proxies which give us information about this field at earlier times. I will present a summary of recent results as obtained from the Kodaikanal digitized archive at IIA. The archive hosts white light, Ca K and H-alpha images for the past century. These images have now been digitized with 4k × 4k CCD and have higher resolution (∼0.86 arcsec) than the other available historical data sets. We have calibrated all these time series and obtained new results which will provide new perspectives.

SSS-2 ASI2016_389 Urmi Doshi Poster

Urmi Doshi(M.P.Birla Institue of Fundamental Research, Bangalore & The Maharaja Sayajirao University of Baroda, Baroda), Ramesh K.B.(Indian Institute of Astrophysics, Bangalore) and Babu G.S.D.(M.P.Birla Institute of Fundamental Research, Bangalore)

On the geomagnetic storms associated with isolated halo CMEs

In the present study, we have analyzed the behavior of 23 moderate to intense geomagnetic storms with Dst (Disturbance Storm Time) ≤ -50 nT that have clearly identifiable Sudden Storm Commencement (SSC) and are specifically associated with isolated halo CMEs (Coronal Mass Ejections) erupted during the years 1997 to 2011. Our analysis with the CME parameters such as speed of the CME (V), latitude & longitude of the source region and the duration for which the Bz (z–component of the Interplanetary Magnetic Field) was southward during the storm phase indicated that the southward turning of Bz before the main phase of the storm plays a vital role in deciding the intensity of the storm, rather than the consistent southward Bz during the actual main phase,. Also, a weak correlation has been noticed between the linear CME speed (V) and the peak amplitude of the storm which may imply that not all intense storms are associated with large CME speeds. Further, we find that helio-latitude regions arethough the CMEs arising from the +/- 30 generally effective in causing the storms, the source regions of CMEs as such do not seem to play a critical role in deciding the strength of the storms.

ASI 2016 – Abstract Book 56

SSS-3 ASI2016_400 Dr. Subhash Kaushik Poster

Karn Singh Parihar School of Physics Jiwaji University

Dynamics of the Geophysical Plasma Events and Their Interplanetary Consequences

In the present study we have analyzed the interplanetary plasma / field parameter, which have initiated the complex nature intense and highly geo-effective events in the magnetosphere. It is believed that Solar wind velocity V. interplanetary magnetic field (IMF) B and Bz are the crucial drivers of these activities. However, sometimes strong geomagnetic disturbance is associated with the interaction between slow and fast solar wind originating from coronal holes leads to create co-rotating plasma interaction region (CIR). Thus the dynamics of the magnetospheric plasma configuration is the reflection of measured solar wind and interplanetary magnetic field (IMF) conditions. While the magnetospheric plasma anomalies are generally represented by geomagnetic storms and sudden ionosphere disturbance (SIDs). The study considers 220 geomagnetic storms associated with disturbance storm time (Dst) decreases of more than -50 nT to -300 nT, observed during solar cycle 23 and the ascending phase of solar cycle 24. These have been analyzed and studied statistically. The spacecraft data acquired by various space missions and those provided by SOHO, ACE and geomagnetic stations like WDC-Kyoto are utilized in the study. It is observed that the yearly occurrences of geomagnetic storm are strongly correlated with 11-year sunspot cycle, but no significant correlation between the maximum and minimum phase of solar cycle have been found. It is also found that solar cycle-23 is remarkable for occurrence of intense geomagnetic storms during its declining phase. The detailed results are discussed in this paper.

SSS-4 ASI2016_405 Pramod Kumar Poster

1. Raj Kumar Choudhary, Affiliation: Space Physics Laboratory, VSSC, ISRO, Trivandrum, India 2. Yogesh C. Bhatt Affiliation: Jagan Nath University, Jaipur 3. Yadvendra S. Shisodiya Affiliation: Jagan Nath University, Jaipur

Statistical analysis of thermal X-ray emission (> 13keV) observed from the X class Solar flares

We present a statistical analysis of thermal X-ray emission (>13 keV) of eight (08) X-class solar flares observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) space craft during 2002-2011. The temporal evolution of each flare in 3-6, 6-12, 12-25, 25-49, 49-100, and 100-250 keV energy bands were analyzed. We find that in most of the flares, there was a gradual rise of X-ray flux in 3-25 keV energy bands. The sudden rise of X-ray flux above ~ 25 keV was observable during the impulsive phase of the flare. This shows that the solar flare plasma has a distribution which in thermal and non-thermal in nature and originates from the thermal and non-thermal X-ray emissions. The cross over energy was found to exist above ~ 25 keV. Further, we carried spectral analysis of each flare using spectral model fitting method over the spectra with reduced chi- square (χ^2) < 3. The spectrum of each flare was divided in 1 minute interval to achieve statistical reliable X-ray spectra. The thermal and non-thermal components of the each spectrum were fitted with the isothermal and thick target models using OSPEX software (consisting CHIANTI and fit function data base). From the fitting, we obtained set of values of plasma temperature, emission measure and non thermal electron flux parameters. Finally we simulated set of plasma parameters using Monte Carlo method and fitted the plasma temperature histogram with the normal distribution function, emission measure and non-thermal electron flux histograms with the exponential distribution functions. We find that most probable plasma temperature lies in ~ 30 MK, emission measure lies in ~ 0-1 x 10^49 /cm3 and non-thermal electron flux lies in ~ 0-500 x 10^35/s bins. ASI 2016 – Abstract Book 57

SSS-5 ASI2016_412 Malik Abdul Waheed Poster

Parvaiz A Khan A.K. Gwal

Effect of solar radiation fluxes on the ionosphere during low and high solar activity

In this study we have studied and compared the response of ionosphere to different solar fluxes during the low and high solar activity periods. For carrying out this study we have a mid latitude station namely Okinawa, Japan (26.3N, 127.8E) and taken the critical frequency of F2 layer (foF2) derived from ionosonde observations to compare the variability of ionosphere during low solar activity period 2007 and high solar activity period 2003. From our analysis, we found that the values of foF2 were low during 2007 and extremely high during 2003, showing that ionospheric activity has a direct relationship with the solar activity. We then took three solar proxies namely F10.7 cm, EUV flux (26-34nm) and X-ray flux (1-8Å) and probed the association of foF22003 and foF22007 with these solar proxies during the minimum and peak of cycle. We found that EUV flux and X-ray flux correlate with the foF22003 and foF22007 much better than F10.7cm, during both the phases of the cycle. Therefore we conclude that EUV and X-ray Flux are better solar proxies than F10.7 which have been widely used in previous studies. Moreover, the correlation of both fluxes (EUV and X-ray) is stronger with fof22003 than with fof22007.

SSS-6 ASI2016_415 Dr Parvaiz Ahmad Khan Poster

Ritesh Yadav A.K. Gwal

The variability of the GPS positional error during quiet and disturbed geomagnetic conditions

The ionosphere, which is considered to be heterogeneous, is the main source of signal transfer medium, which brings about the possibility of radio communication over large distances by making use of one or more ionospheric reflection. Therefore estimating the ionospheric conditions in the real time would be of great use to communication and navigation system operators, since ionospheric disturbance can adversely affect radio propagation through attenuation, fading, absorption, noise, or signal velocity change. Due to such changes the navigation system miscalculates the distance of the signal path, creating navigational error. In the present study we have studied the behaviour of the positional error during geomagnetically quiet and disturbed conditions. In our investigation we have used the data collected at a high latitude Indian station, Maitri (70.4° N, 11.4° E), Antarctica during the low solar activity period i.e. 2006. We then selected five most disturbed days as well as five quiet days of the month. For each disturbed and quiet day we calculated the absolute positional error in meters. The dilution of precession parameters namely PDOP were also derived for each day. We found that the value of absolute positional error and PDOP is significantly increased during the disturbed days.

ASI 2016 – Abstract Book 58

SSS-7 ASI2016_416 Nishtha Sachdeva Poster

Prasad Subramanian Indian Institute of Science Education and Research (IISER), Pune.

Propagation of Coronal Mass Ejections

We aim to understand the contributions of driving and drag forces on Coronal Mass Ejections (CMEs) ejected from the Sun. Observations of CME kinematics are derived from STEREO data fitted to the Graduated Cylindrical Shell (GCS) model. We use a physical prescription for the aerodynamic drag experienced by CMEs as they travel from the Sun to the Earth. We find that the kinematics of relatively slow CMEs are dominated by solar wind drag only beyond 15--50 solar radii. They are likely propelled by Lorentz forces below these distances. We attempt to understand the details of these Lorentz driving forces using the popular torus instability model. Taken together, our work will form the basis of a comprehensive, physics-based model for the dominant forces responsible for Sun-Earth CME propagation.

SSS-8 ASI2016_422 Bhupendra Kumar Tiwari Poster

B.K.Tiwari Department of Physics A.P.S.University, Rewa (M.P.)INDIA

Heliospheric Modulation of Galactic Cosmic Rays during Solar Minimum of solar cycle 23/24

Heliospheric Modulation of Galactic Cosmic Rays during Solar Minimum of solar cycle 23/24 B. K. Tiwari Department of Physics, A. P. S. University, Rewa (M.P.), [email protected] Galactic cosmic rays (GCRs) flux at earth is modulated by the heliosphereric magnetic field and the structure of the heliosphere, controls by solar outputs and their variability. Sunspots numbers (SSN) is often treated as a primary indicator and 10.7 cm solar radio flux are an important gauge of solar activity (SA). GCRs entering the helioshphere are affected by the interplanetary magnetic field (IMF) and solar wind speed, their modulation varies with the varying solar activity. The observation based on data recoded from Omniweb data Centre for solar- interplanetary activity indices and monthly mean count rate of cosmic ray intensity (CRI) data from neutron monitors of different cut- off rigidities(Rc) (Moscow Rc=2.42GV and Oulu Rc=0.80GV). During minimum solar activity period of solar cycle 23/24, the sun is remarkably quiet, weakest strength of the IMF and least dense and slowest, solar wind speed, whereas, in 2003, highest value of yearly averaged solar wind speed (~568 Km/sec) associated with several coronal holes, which generate high speed wind stream has been recorded. It is observed that GCRs fluxes reduces and is high anti-correlated with SSN (0.80) and IMF (0.86). Modulation in CRI produces by a strong solar flare, however, CME associated solar flare produce more disturbance in the interplanetary medium as well as in geomagnetic field. It is found that count rate of cosmic ray intensity and solar- interplanetary parameters were inverse correlated and solar indices were positive correlated. Keywords- Galactic Cosmic rays (GCRs), Sunspot number (SSN), Solar activity (SA), Coronal Mass Ejection (CME), Interplanetary magnetic field (IMF)

ASI 2016 – Abstract Book 59

SSS-9 ASI2016_463 mahender aroori Poster

G. Yellaiah K. Chenna Reddy Department of Astronomy Osmania University Hyderabad

CORRELATION STUDIES BETWEEN SOLAR RADIO FLUX IN DIFFERENT FREQUENCIES AND SUNSPOT NUMBERS DURING THE SOLAR CYCLE 23, 24 The 11-year solar cycle is characterized by the changes in the sunspot numbers. The relationship between solar radio flux at 10.7 cm (2800 MHz) and the sunspot numbers during the solar activity cycle has been quantified by many authors. Here we present the correlation studies between the monthly mean solar radio fluxes at 15400 MHz, 8800 MHz, 4995 MHz, 2800 MHz (10.7 cm), 2695 MHz, 1415 MHz, 610 MHz, 410 MHz and 245 MHz with the sunspot numbers during the solar cycles 23 and 24, using the 'Solar Indices Bulletin' data which provides the solar flux along with the sunspot numbers. This is the most widely used indices of solar activity. These studies would help in understanding the general trend during the current solar cycle activity and further explain the future solar cycles.

SSS-10 ASI2016_486 Megha A Poster

A. Megha(2), K. Sankarasubramanian(1, 2), , Jagdev Singh(2), M. Sampoorna(2), and K. N. Nagendra(2) (1) Space Astronomy Group, ISRO Satellite Centre, Bengaluru (2) Indian Institute of Astrophysics, Koramangala, Bengaluru

Coronal Plasma Diagnostics using Visible and Near-IR Coronal Emission Lines

Solar Corona consists of high temperature dynamics plasma (of the order of Million degree). The physical parameters of the coronal plasma (viz. Temperature, densities, magnetic field etc.) are dynamic. Though it is well known that the average temperature of the plasma is about Million degree, it changes drastically during eruptive events like flares and CMEs. Even during quiet period, the volume of plasma is considered to be multi-thermal (i.e., more than one temperature inside the volume). Simultaneous spectroscopy of multi spectral line is the best diagnostic method in order to study such a dynamic plasma. The physical parameters of the plasma are derived using line ratio methods. In this work, we incorporate a forward modeling technique for the observed data using the CHIANTI databases and its spectral synthesis capabilities. The motivation behind this work is to study the feasibility of generating an inversion procedure for spectral lines formed in solar coronal plasma like it is carried out for the photospheric and chrmospheric spectral lines. This study includes the derivation of the major plasma parameters - Temperature, densities and Emission Measures. This study would also discuss the forward modeling for coronal magnetic field observations and hence help with the data from the upcoming Aditya mission. The sailent advantages and disadvantages of this methodology would also be brought out in this study.

ASI 2016 – Abstract Book 60

SSS-11 ASI2016_494 Akshay Suresh Poster

Akshay S. (1), Rohit Sharma (2), Srijan B. Das (3), Divya Oberoi (2) and Victor Pankratius (4) 1 - IISER Pune, India 2 - NCRA-TIFR, Pune, India 3 - IISER Kolkata, India 4 - MIT Haystack Observatory, MA, USA

Statistical analysis of weak solar bursts seen with the Murchison Widefield Array

Numerous short-lived low, narrowband weak radio solar bursts have been identified in data from the Murchison Widefield Array (MWA), even during quite solar conditions. These emission features must come from non-thermal processes and their appearance in the dynamic spectra is unlike that of the well-established classes of radio bursts. We have been investigating the possibility of these emission features being electromagnetic signatures of the so called "nanoflares" hypothesised as a solution to the coronal heating problem. Given the large data volumes and rates of occurrence of these features, an automated approach is essential for their characterisation. Here we use wavelet decomposition approach to develop a technique to quantify the nature of these emission features and apply it to MWA data. This work builds on earlier work by the members of this collaboration to achieve a reliable flux calibration in a computationally efficient manner, and also allows us to characterise the slow variations in the solar thermal background emission.

SSS-12 ASI2016_505 Ajay Kumar Tiwari Poster

Ajay Tiwari,IISER PUNE Vaibhav Pant, IIA Bangalore, Rakesh Mazumdar,IIA Bangalore and Dipankar Bannerjee IIA Bangalore.

standing oscillations in coronal loops and plumes as seen from AIA/SDO

We report standing oscillations in coronal loops and plumes as seen from AIA/SDO. We find that oscillations are triggered by the incoming shock wave generated from nearby flare. The incoming shock hit and compress the plasma inside the coronal loop and the plume, thereby triggering the standing slow wave. We also find that these oscillations are damped. We performed the DEM analysis and estimated the temperature and density inside these structures. This phenomena is ubiquitous and if initial conditions are right then these structures can support standing slow waves. Some initial observational results and simulations will be presented.

ASI 2016 – Abstract Book 61

SSS-13 ASI2016_526 Avijeet Prasad Poster

Magnetic helicity and force-free properties of astrophysical magnetic fields

The Thesis applies novel techniques and formulae for magnetic helicity and non-linear force-free field (NLFFF) to two different astrophysical settings: the solar corona and disc galaxies. The solutions obtained in the solar case provide alternate and verifiable means to calculate the structure and energetics of active regions (ARs). Further the topological methods provide a deeper understanding of the sources of coronal heating. In the case of the disc galaxies, our analytic treatment provided a transparent and powerful use of eigen-functions that yielded a full global solution to the galactic dynamo and its route to saturation. Complementing these solutions with future numerical models can give further insight and drive us to better models in both cases. The specific novel results are: We provided a new formulation for relative helicity in arbitrary geometries using the toroidal-poloidal representation. In the case of the solar corona, we solved linear and NLFFF equation using photospheric boundary conditions to obtain simple axisymmetric magnetic field configurations in spherical geometry and applied it to the AR 10930 and we confirmed in both models a substantial decrease in free energy and relative helicity after the flare, which is in agreement with those obtained from other numerical methods. We tested a model of self-organized criticality for the distribution of coherent braid sequences by comparing the resulting distribution of peak-flare energies with those obtained from NLFFF extrapolation. The results indicate that a significant component of the energy budget for coronal heating can potentially be supplied by nano-flares during reconnection of magnetic braids in the case of the active Sun. For the galactic dynamo, we have introduced the following novelties: building a three-dimensional model of the global field of the disc and corona using a simplified treatment of reconnecting the small-scale field to describe a large-scale force-free coronal field and balancing the global helicity by the use of gauge-free descriptions of absolute helicity and incorporated the radial dependence in the supernovae and MRI- driven turbulence parameters under a common formalism. The time-dependent solution is expressed in a separable form, with the radial part in terms of the steady-state counterparts. These global analytic solutions allowed us to calculate the field structure and evolution of relative helicity for both the disc and the corona. The resulting saturated quadrupolar magnetic field is of the order of its equipartition value (the 99% value is reached in about a Gyr, which is faster than the timescales reported in previous simulations) and proportional to the advective and diffusive fluxes.

SSS-14 ASI2016_541 SAMRAT SEN Poster

A. Mangalam, Indian Institute of Astrophysics

Model of a flux tube with twisted magnetic fields

We assume a single open magnetic flux tube spanning the solar photosphere and the lower corona in magnetohydrostatic equilibrium within a realistic stratified atmosphere subject to solar gravity. We explore variants of the self-similar sunspot model with twisted magnetic fields. The analytical solution of the variation of magnetic field strength with the depth is used to derive the run of plasma density and pressure. The aim is to apply this model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona taking realistic inputs of field strength and pressure distribution observed in the lower solar atmosphere.

ASI 2016 – Abstract Book 62

SSS-15 ASI2016_595 Rahul Yadav Poster

Shibu K Mathew (Udaipur Solar Observatory/PRL)

The relation between Umbral Dots and phase of Sunspot

Understanding the stability and decay of the sunspots is a major problem in modern solar physics. The properties of umbral dots (UDs), which are important part of the sunspot structure, play a crucial role in this direction. UDs are dot-like bright features observed in almost all sunspot umbrae and pores. Based on their location, UDs are classified as peripheral umbral dots (PUDs) and central umbral dots (CUDs). They are thought to be manifestations of magnetoconvection in sunspot umbrae. Objective of this work is to determine if there is a relationship between UDs properties and phase of sunspot. We employ high-resolution G-band filtergrams observed for six regular isolated sunspots from the Solar Optical Telescope (SOT) on board Hinode at the spatial resolution of 0.0541 arcsec/pixel. We examine the decay rate and phase of sunspots from SoHO/MDI 6-hrs full disk continuum images. The MDI continuum images are first corrected for the limb- darkening, stray-light and then flat-fielded prior to determine the decay rates of sunspots. We apply an image segmentation method and object tracking algorithm on a series of the G-band filtergrams in order to analyse the UD properties. It is found that the decay rates of sunspots vary from 0.023 to 0.06 million km 2 /hr and the effective diameter value of CUDs and PUDs is 0.22 (0.042) arcsec and 0.33 (0.04) arcsec, respectively. Further we observe that there is no clear correlation between decay rate and effective diameter of UDs. However, we notice correlation between the decay rate and UDs density.

SSS-16 ASI2016_599 Tomin K James Poster

Prasad Subramanian, IISER Pune

Elemental electron acceleration at sun

We aim to estimate the energy involved in elemental electron acceleration episodes in the solar corona. We fit the observed electron distribution to a Kappa distribution function, which seamlessly integrates thermal and non-thermal characteristics. Using a steady-state Fokker-Planck equation to describe the stochastic acceleration of electrons, we find that the energy involved in each electron acceleration spike normally around 10^21 ergs/s. To understand the acceleration of the energetic particles at the acceleration site we compare hard X-ray photon spectra observed by RHESSI with the near-earth electron spectra of the associated events measured using the EPAM experiment aboard ACE spacecraft. We find a positive correlation, suggesting same physical mechanism responsible for the acceleration process of the HXR producing electrons and the electrons escaping from the acceleration site.

ASI 2016 – Abstract Book 63

SSS-17 ASI2016_639 Gopal Hazra Poster

Mark Miesch, High Altitude Observatory,Boulder

A Three-Dimensional Babcock-Leighton Solar Dynamo Model with Non-Axisymmetric Subsurface Flow

The study of photospheric magnetic field evolution is very important because it is the only observable part of the Babcock-Leighton dynamo models and it sets the boundary condition for the coronal and heliospheric magnetic fields. Observationally it is evident that the solar photospheric magnetic fields is mostly transported by the large scale and small scale surface flows i.e, Differential Rotation, Meridional Circulation and Convective flows ( granular and supergranular flows ). Presently most of the Babcock-Leighton Models use only the axisymmetric flows of sun. We are now incorporating the non-axisymmetric convective flows in our model also which are based on the observation of doppler measurement of the solar photosphere. From observation we have only the velocity measurement of the photosphere which is mainly horizontal flows on the surface but our model is a 3D model so we have extrapolated the horizontal surface flows radially below the photosphere inside the convection zone assuming that the mass flux is divergenceless. Since we have incorporated large scale and small scale velocity field simultaneously, the evolution of radial magnetic field on the surface of the sun more closely matches the observation. Convective velocity fields are mostly responsible for diffusive transport of flux on the solar surface also, so at last we run some simulations varying the diffusivity of the surface so that we can have some estimate of the diffusion co-efficient which reproduce the results including the convective flow fields.

SSS-18 ASI2016_665 Jishnu Bhattacharya Poster

Shravan M. Hanasoge, Tata Institute of Fundamental Research

Strategies in seismic inference of supergranular flows on the Sun

Observations of the Solar surface reveal the presence of flows spanning tens to hundreds of mega-meters, commonly referred to as supergranules. Inferring the sub-surface flow profile of supergranules from measurements of the surface and photospheric wavefield is an important challenge faced by helioseismology. Traditionally the inverse problem has been approached through linear kernels (Gizon et al., 2002; Dombroski et al., 2013); however it is believed that an iterative approach would perform better than single-step, linear inversions (Hanasoge, 2014). In this paper, we simulate `observed wavefield' starting from a specific 2- dimensional supergranule profile (Duvall et al., 2013), and use the SPARC code (Hanasoge et al., 2007) to update our model of the flow by iteratively reducing the travel-time misfit between the `observed wavefield' and the one predicted by our model. We investigate the impact of strategies such as spatio-temporal and spectral filtering on the accuracy and speed of convergence of the inversion. We show that the inversion proceeds through correcting surface layers before deeper layers, and that large-distance measurements or equivalently high-order p-modes are necessary to infer the profile of the flow beyond the depth of a mega- meter. We demonstrate that limited depth sensitivity leads to inaccurate estimation of velocity magnitudes, especially for vertical component of velocity.

ASI 2016 – Abstract Book 64

SSS-19 ASI2016_734 Arshiya A Poster

Authors: A. Arshiya1, M Nuthan1 & B. Ravindra2 Affiliation: 1 Christ University, Bengaluru 2 Indian Institute of Astrophysics, Bengaluru

Short and Long term periodicity in sunspot area and number

Apart from 11 year periodicity, the sunspot area and number exhibits short and long term periodicity. Using 140 years of sunspot area and number data we identify several periodicity in the northern and the southern hemisphere of the sun. Along with 160 day periodicity we found 1-year, 2-year and longer time period periodicity in both the hemisphere. In this poster we show the results of different periodicity observed in the sunspot area and number data of both the hemisphere of the sun. These results could be useful for understanding the underlying mechanisms of the observed periodicity.

SSS-20 ASI2016_775 SUDIP Poster

D. Banerjee, Indian Institute Of Astrphysics, E. Scullion, Northumbria University, V. Fedun, University of Sheffield, S. Regnier, Northumbria University

DYNAMICS OF A GIANT SPIRAL

Study of magnetic field configuration and its evolution, is an important aspect towards understanding the various solar activities happening in the solar atmosphere . In this context, We study a spiral like magnetic structure, observed with 1-meter Swedish Solar Telescope (SST) which shows counter streaming flows on different 'spines'. Also, a classical 'X' like null point is present at the heart of this structure which beautifully manifests the complexity of this configuration. We analyse this high spatial and temporal resolution data to better understand and model such magnetic configuration and their evolution over time.

ASI 2016 – Abstract Book 65

SSS-21 ASI2016_798 Divya Oberoi Poster

Rohit Sharma, NCRA-TIFR Alan E. E. Rogers, MIT-Haystack Observatory, Westford, MA, USA

Estimating the flux density and the brightness temperature of the Sun using a sky brightness model

The new generation interferometric arrays are very well suited for spectroscopic imaging studies of the Sun. However the processing of these data with the high time and frequency resolution needed to capture the variations in solar radio emission is prohibitingly expensive in terms of both human and computational effort involved. Already the Murchison Widefield Array (MWA) project has amaased about 1.8 PB of solar data. There is, hence, a strong motivation to develop an automated and computationally lean analysis technique capable of extracting physically interesting information from these voluminous data. To meet this objective we have developed an approach to arrive at a flux density of the Sun using a sky model using the normalized cross-correlations (visibilities) measured on a low resolution interferometric baseline. This technique makes use of the fact that the MWA is a fairly well characterised instrument and the availability of a detailed and reliable model for the sky brightness distribution. Here we apply this technique it to data from the MWA and establish its robustness and reliability at determining solar flux density and average brightness temperatures. The ability of this technique to be able to estimate solar flux reliably with the native time and frequency resolution of the data provides us a very useful tool for studying the energetics of the weak short lived and narrow band emission features seen in the low radio frequency data. Some of its applications will be presented elsewhere in this meeting.

SSS-22 ASI2016_897 Aabha Monga Poster

Dr. Wahab Uddin, ARIES Nainital Dr. Ramesh Chandra, DSB Campus, Kumaun University, Nainital

Spatial and Temporal enhancements in Eruptive events

In this paper, I have analyzed the region AR 12437 where C 2.1 class flare occurred in the South-West area of the Sun observed on October 26, 2015. From the morphological studies, flare eruption shows the Three ribbon structure. This region was least complex with the complexity α. Filament was associated with this flare. Besides the circular ribbon, an inner and an outer (remote) ribbons are often found. To explore the driver of instability leading to this highly energetic flare, we study the morphological evolution of the AR employing multi-wavelength observations from Solar Dynamic Observatory (SDO) and STEREO. I do not found any signature of the CME associated with this flare. I have also done its spectral analysis for the This study is also characterized with the X-ray emission to study the energy release processes. I have also used ARIES Hα data and velocity Dopplergrams for the Photospheric study of the region AR11748 for the Intensityvelocity relations.

ASI 2016 – Abstract Book 66

SSS-23 ASI2016_930 Rakesh Chandra Narwa Poster

Rakesh Chandra N MJCET, Hyderabad. G. Yellaiah Osmania University, Hyderabad

Statistical analysis of meteoroid fragmentation during the Geminid and Leonid Meteor showers

Meteoroid mass is deposited in the upper atmosphere either through fragmentation or through differential and simple ablation mechanisms.Each mechanism deposits the flux in different form ( dust/ smoke - fragmentation, atomic form - ablation). Our observations using MST Radar (at NARL,Gadanki, India), disclosed an important out come that during the Geminid Meteor shower (parent body - Phaethon 3200) the percentage of meteoroid fragmentation (12%) is lower than that observed during Leonid meteor shower(24%)(parent body - comet 55P/ Tempel - tuttle). This outcome is thought provoking as their parent bodies are different, the first shower being asteroid originated and the later being comet originated. The two parent bodies has different chemical constituents. The mass of the meteoroids observed during each of the above showers are different. We may conclude that percentage of meteoroid fragmentation is different for different showers and also depends on the mass of the incoming meteoroids. These results will also contribute in improving current meteoroid disintegration/ablation models.

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ASI 2016 – Abstract Book 67

ASI-2016 Poster Presentations

Stars, The Milky Way Galaxy and its neighbours

SG-1 ASI2016_384 Ranjan Gupta Poster

D.B. Vaidya Ex-Gujrat College, Amdavad

Light Scattering tools to understand effects of dust in astrophysical environments

The talk will describe the basics of light scattering phenomena in the context of observations of astrophysical dust and its consequence. Several tools are now available to explain the astrophysical observations of extinction; polarization and NIR emission and these tools will be inter-compared for their benefits when applied to a dust environments.

SG-2 ASI2016_409 KALYANI BAGRI Poster

Ranjeev Misra (IUCAA),J.S.Yadav (TIFR),S.K.Pandey (PTRSU,Raipur)

A systematic analysis of the low/hard state RXTE spectra of GX 339-4 to constrain the geometry of the system

One of the popular models for the low/hard state for Black Hole Binaries is that the standard accretion disk is truncated and the hot inner region produces via Comptonization, the hard X-ray flux. This is supported by the value of the high energy photon index which is often found to be small ~1.7 < 2, which implies that the hot medium is seed photons starved. On the other hand, the suggestive presence of a broad Iron line during the hard state would indicate that the accretion disk is not truncated but extends all the way to the inner most stable orbit. In such a case, it is a puzzle why the hot medium would remain photon starved. The broad Iron line should be accompanied by a broad smeared reflection bump at ~30 keV and it maybe that this additional component makes the spectrum hard and the intrinsic photon index is larger, i.e. > 2. This would mean that the medium is not photon deficient, reconciling the presence of a broad Iron line in the hard state. To test this hypothesis, we will analyze the RXTE observations of GX 339-4 during the 2002-2003 outburst and identify the observations when the system was in the hard state and showed a broad Iron line. We will then attempt to fit these observations with models which include smeared reflection to understand whether the intrinsic photon index can indeed be large. We will present the results of this analysis and other correlations between spectral parameters such as the flux, ionization level, Equivalent Width of the line, etc.

ASI 2016 – Abstract Book 68

SG-3 ASI2016_418 Krishna Kumar Kowshik Poster

Komala S, Aahut Chandwani, Sujatha S. Babu G.S.D M.P.Birla Institute of Fundamental Research

Mass Function of open clusters NGC 2254 and Kronberger 1

We present the results of the UBVRI CCD photometry combined with the analysis of 2MASS JHKs archival data of the open clusters NGC 2254 and Kronberger 1 situated in the Galactic anti-center region. NGC 2254 and Kronberger 1 are located in the direction of Monoceros and Auriga constellations with a radial extent of 4 and 3 arcmin respectively. From the analysis of the two-colour diagrams the colour excess E(B-V) for NGC 2254 is estimated to be 0.53±0.05 mag while for Kronberger 1 it is 0.445±0.05 mag. The ZAMS and isochrones of solar metallicity were used to fit the main-sequence of the colour-magnitude diagrams to determine the distance and the log (age) of the clusters. The log (age) of the clusters NGC 2254 and Kronberger 1 are estimated to be 8.45 and 7.65 while they are placed at a distance of 2.57±0.5 kpc and 2.511±0.5 kpc respectively. The slope of mass function for NGC 2254 is found to be -2.45±0.3 and -2.62±0.18 for Kronberger 1, which are in fair agreement with the Salpeter value.

SG-4 ASI2016_419 Komala S Poster

Sujatha S, Krishna Kumar K, Babu G.S.D. M.P.Birla Institute of Fundamental Research.

First UBVRI CCD photometry of the open cluster Mayer 2

In this paper we present deep UBVRI CCD photometry of the not-so-well studied open cluster Mayer 2. This cluster, with a radial extent of 3 arcmin, is located at a distance of 4.46 ± 0.5 kpc in the direction of Camelopardalis constellation. The interstellar extinction E(B-V) in the line of sight of the cluster is estimated to be 0.645±0.5 mag. From the appropriate theoretical isochrones of solar metallicity, the log (age) of the cluster is found to be 8.55. To substantiate the results obtained through optical data we have compared them with the near infrared 2MASS archival data and they are found to be in good agreement. The luminosity function was constructed using the likely and probable members and it indicates the common trend of the number of stars increasing towards the fainter magnitudes.

ASI 2016 – Abstract Book 69

SG-5 ASI2016_431 Shruthi S Bhat Poster

Shruthi S Bhat, Christ University Paul K. T., Christ University Annapurni Subramaniam, Indian Institute of Astrophysics

High resolution spectroscopy of Classical Be stars

We present the preliminary results of high resolution spectroscopic study of 17 Classical Be stars observed using the echelle spectrograph at 2.3m Vainu Bappu Telescope, VBO, Kavalur. All the stars were observed in the wavelength range of 4100 - 10800 Å during 2010 and 2011. We obtained a total of 44 spectra of resolution ~27000. Classical Be stars are known to show emission due to the circumstellar disk formed by the ejection of mass from the central star. All the selected Be stars showed Hα emission line. Other emission lines seen in the spectra were Hβ, Hγ, HeI, OI and CaII. From the spectra, different emission line parameters and stellar parameters have been deduced. We discuss the correlations between different pairs of these parameters with a view to understand the emission line characteristics in Be-stars.

SG-6 ASI2016_433 Priyanka Chaturvedi Poster

Abhijit Chakraborty (PRL, Ahmedabad) B.G. Anandarao (PRL, Ahmedabad)

Detection of two M dwarfs in F+M detached eclipsing binary systems with radial velocity measurements from PARAS

Stellar systems gravitationally bound to each other where the orbital plane is inclined in a way that one component passes in front of the other causing variations in brightness are known as eclipsing binaries (EBs). Accurate determination of masses, radii, age and chemical composition of stars is possible to be studied in EBs which is important to study stellar structure and evolution. M dwarfs (having masses less than 0.6 M_sun) are studied poorly due to their relative faintness in the visible bands. A vast majority of M dwarfs have reported a higher value for radius determined observationally by 10 - 20 % in comparison with the theoretical models, an issue termed as 'M dwarf radius problem'. This discrepancy is more prevalent in the mass range of 0.3 - 0.4 M_sun, which forms a boundary between completely convective and partially radiative stars. M dwarfs which occur as companions to bright F, G and K type stars can be studied with radial velocity (RV) and transit photometry for determination of masses and radii at high accuracies with an aim to resolve the M dwarf radius problem. We report one such study of two EBs (STEREO-PARAS 2 and SWASP-PARAS 2) shortlisted from STEREO and SuperWasp (SW) photometry catalogues consisting of F type main sequence primaries and putative M dwarf secondaries. The RV measurements for both the sources have been made by the indigenously built spectrograph, PARAS (Physical Research Laboratory Advanced Radial velocity Abu Sky search), an optical fiber-fed high-resolution spectrograph coupled with the 1.2 m telescope at Mt. Abu, India. The photometry data for STEREO-PARAS 2 have been retrieved from SW. Based on high resolution spectroscopy and photometry measurements, the mass and radius for the M dwarf secondary is 0.393 M_sun and 0.449 R_sun respectively derived at an accuracy of 7 - 8 % indicating that the secondary is a M3 dwarf. The value of radius determined from observation is around 15% higher than the value predicted from theoretical models. For the second EB, SWASP-PARAS 2, the mass of the M dwarf is 0.254 M_sun. The estimated radius value based on SW photometry is 0.12 R_sun which is half the value from theoretical predictions. Noisy SW photometry may have led to erroneous determination of radius. We aim to follow this source in future for accurate determination of radius. The F+M EBs, STEREO-PARAS 2 and SWASP-PARAS 2 have periodicity of 1.686 days and 4.242 days respectively and peculiar eccentricity of around 0.25 and 0.3 respectively which are atypical for EBs in short orbital periods. The observations, analysis methods and interpretation of results for this EB system will be presented along. ASI 2016 – Abstract Book 70

SG-7 ASI2016_440 Akshaya Subbanna M S Poster

Akshaya Subbanna M S, Christ University, Bengaluru Ravichandran. S, Christ University, Bengaluru Jayant Murthy, Indian Institute of Astrophysics, Bengaluru

Modelling of the dust scattered halos observed around bright stars

Interstellar dust plays a major role in the formation of stars and the evolution of a galaxy. However, various properties of interstellar dust grains are poorly understood. The optical properties of the interstellar dust grains are mainly described using two parameters - the albedo (a) and the phase function asymmetry factor (g). We have derived these properties using the halo observed around bright stars, which is due to the scattering of starlight by dust located between us and the star. A thorough analysis of such halos around bright stars can yield useful information regarding the properties and distribution of dust grains in our Galaxy. We selected four stars which were known to have UV halos and modelled the UV emission around them. The brightness and the extent of the observed halos depend on a number of parameters such as, the intrinsic luminosity of the star, optical properties of the grains, the distance between the star and the dust, the density of dust grains in the scattering layer and scattering cross section of the grains. UV data from the Galaxy Evolution Explorer (GALEX) and IR data from Infrared Astronomical Satellite (IRAS) and Planck were used for the halo modelling. We present here the derived optical properties and the distribution of the dust grains obtained from the modelling of the four stars.

SG-8 ASI2016_442 Ranjani.L.Kandi Poster

(2) K T Paul, Christ University, Hosur Road, Bangalore 560029,[email protected] (3)Annapurni Subhramaniam, Indian Institute of Astrophysics, Bangalore 560034,[email protected] (4)Shruthi Bhat ChristUniversity,Hosur Road, Bangalore560029, [email protected]

Long term variability of Hα emission line profiles in selected Be-Stars

A Be star is a non-super-giant B type star whose spectrum has, or had at some time, one or more Balmer lines in emission. It is widely accepted that Be stars are rapidly rotating stars surrounded by disks or ring-like envelopes in the equatorial region, where the emission lines are formed. These disks are formed due to the decretion of mass from the central star. Investigation of Hα emission line reveals important information about the circumstellar disk parameters and their variability over a period of time. The Be-phenomenon or the B <-> Be phase is not yet understood very clearly. Long term and gradual variations of the circumstellar emission & absorption lines are common to all Be stars. In addition, there is also more rapid (short-term) variability observable both in photometry and spectroscopy. The most common emission line profile seen for the Be stars is the double-peaked Hα line. For these type of profiles, V/R variations are the most common type of variability. The V/R variations are said to be periodic on a long term basis. We present a set ofspectroscopic study of 25 program stars of double peaked emission line profile, available in the BeSS database. This database contains the complete catalog of classical Be stars and Herbig Ae/Be-stars, and assembles spectra. The required spectroscopic parameters such as EW, FWHM, V/R will be obtained for each of the stars, using which the disk radius will be calculated in terms of the stellar radius. The period of long term variability will also be determined and correlations between the spectroscopic parameters will be established.

ASI 2016 – Abstract Book 71

SG-9 ASI2016_443 Preethi K Poster

K. Preethi 1, Jayant Murthy 2, S. B. Gudennavar 1, S. G. Bubbly 1, Noah Brosch 3, 1 Department of Physics, Christ University, Bengaluru 560 029, Karnataka, India, 2 Indian Institute of Astrophysics, II Block, Koramangala, Bengaluru 560 034, Karnataka, India, 3 The Wise Observatory and the School of Physics and Astronomy, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel

White Dwarf Catalogue & Extinction Map

A study of the interstellar medium (ISM) enables us to understand the structure, dynamics and energetics of our Galaxy while also affecting astronomical observations. We now have many observations from space-based and ground-based telescopes. Our goal is to compile and analyse these data, study the ISM on a larger scale and make the database available to the scientific community for further investigations. We have extracted photometric data from Galaxy Evolution Explorer (GALEX) General Release 6 (GR6) and Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) for over 1.67 million point sources classified as stars by SDSS based on their point spread function. Our preliminary analysis showed 80% of these point sources to be extragalactic and that a colour-cut based method cannot distinguish between stars and galaxies/quasars. We instead adopted a model based approach to classify all sources by type, determine the distance towards the Galactic objects, photometric redshift towards galaxies and quasars, and line of sight extinction. Our model fitting gave us 0.40 million white dwarfs, ~60,000 main-sequence stars, ~20,000 red-giants, 0.34 million quasars and 1.19 million galaxies. Of these, we only included white dwarfs brighter than 22 magnitudes in all bands and with 90% confidence in chi square. We also excluded all sources outside the white dwarf (u−g, g−r) colour space to eliminate any horizontal-branch and blue straggler stars giving us a sample of 35,379 white dwarfs which is the focus of this work. The number and spatial distribution of these white dwarfs were studied and their thin-disk scale height estimated to be 349 pc and 286 pc, above and below the Galactic disk respectively. Based on this catalogue of white dwarfs, we have derived three dimensional extinction maps of our Galaxy in distance steps of 100 pc and in bins of 1 square degree. The map extends to a distance of 800 pc and covers an area of 13,441 square degrees (~32% of the sky). The extinction as a function of Galactic latitude and distance was studied. We have compared our results with the integrated extinction map by Schlegel et al. (1998). We find our extinctions to be underestimated at low latitudes and overestimated at high latitudes as compared to that from Schlegel et al. (1998) and find the median in the difference to be 0.025 mag.

ASI 2016 – Abstract Book 72

SG-10 ASI2016_451 Apara Tripathi Poster

Brijesh Kumar* U.S. Pandey** S.N.Tiwari** * Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263129, India ** Department of Physics, Deen Dayal Upadhyaya Gorakhpur University, Gorakhpur, Uttar Pradesh 273009, India

A homogeneous photometric catalog of Eight Open star Clusters

Open star clusters are excellent targets to understand issues related to galactic structure, stellar population, dynamical evolution, and star formation process in the Galaxy. We present new UBVRI photometric catalog for eight open star clusters, i.e. for NGC 6793, NGC 6800, NGC 1027, NGC 2129, NGC 1502, NGC 6531, King 12 and NGC 2467. Many of these clusters are poorly studied. The data is collected from 104-cm Sampurnanand Optical Telescope, ARIES Nainital, using 2kx2k CCD which covers about 13x13 arcmin square field on sky. The data reduction is done in homogeneous manner and a global catalog of all the stars in the observed field have been generated. We are able to reach down to ~ 21 mag in V band. Variability data as well as Hα have also been taken for few clusters. The study aims to determine member stars of clusters using the present catalog as well as the archival astrometric catalog. This homogeneous set of data will help us to determine the fundamental parameters (distances and ages) and the mass function of clusters.

SG-11 ASI2016_457 NAVEEL AHMAD WANI Poster

Naveel Ahmad Wani, Ranjeev Misra and Naseer Iqbal

Effect of Multi-stochastic Perturbations on the behaviour of Accretion Discs

We want to study the structural changes which occur in the accretion disc in the x-ray binaries on the basis of standard α-disc model. In x-ray binaries, x-rays are emitted from the inner regions while uv emission could arise from the relatively cooler outer parts of the disc. There is now increasing evidence that the variability of the x-rays is caused by stochastic fluctuations in the accretion disc at different radii. These stochastic fluctuations arising in the outer parts of the disc, but on propagating inwards gives rise to x-ray variability and thus naturally relates the x-ray and uv variability. There are analytical expressions to qualitatively understand the effect of these stochastic variabilities, but quantitative predictions are only possible by a detailed hydrodynamical study of the global time dependent standard accretion solution. In this direction, we developed a numerically efficient code to incorporate the various effective process of the disc like gas pressure and stochastic fluctuations with the boundary effect of the last stable orbit. The code has been tested for numerical stability.

ASI 2016 – Abstract Book 73

SG-12 ASI2016_461 Sowgata Chowdhury Poster

Sowgata Chowdhury, Student, Department of Physics, Christ University Dr. Santosh Joshi, Scientist D, ARIES, Nainital Dr. Yogesh C. Joshi, Scientist D, ARIES, Nainital Prof. K. T. Paul, Professor, Christ University Prof. C. A. Engelbrecht, Professor, University of Johannesburg, South Africa

Pulsation and Rotation of A-K type stars in the Kepler field

We present the results of time-series photometric analysis of about 15000 A-K type stars observed by the Kepler space mission. We measured starspot rotation periods of 2373 active stars as a function of spectral type and also discuss the distribution of their amplitudes. We examined the period-color relationship for all the Kepler field rotational variables ranging from spectral type K7 to A0 and interestingly found that the same relationship holds true for both early-F and A type stars. This result is not consistent with the very foundation of the PtM relationship. Through visual inspection of the light curves and their corresponding frequency spectra, we identified 16 stars with solar-like oscillations that had previously been classified in the literature as red giants. In addition, we found 71 new candidate solar-like oscillators not previously reported in the literature. The basic physical parameters such as masses, radii and luminosities of these solar-like oscillators were also derived using asteroseismic relations. We have characterized several non-radial pulsating variables such as δ Sct, γ Dor and hybrid stars. The relationship between two newly constructed observables, ‟Energy‟ and ‟Efficiency‟ was also studied for the large sample of non-radial pulsators. Our results also support the idea that the present observational instability strip should be extended to accommodate the newly discovered pulsators.

SG-13 ASI2016_462 Nayana A J Poster

Poonam Chandra (NCRA-TIFR) Subhashis Roy (NCRA-TIFR)

Discovery of 325 MHz and 610 MHz radio counterpart of Supernova Remnant HESS J1731-347 a.k.a SNR G353.6-0.7 Supernova shocks are suggested as probable candidates of cosmic ray acceleration sites, through a mechanism called Diffusive Shock Ac- celeration (DSA). A TeV source associated with Supernova Remnant (SNR) becomes an interesting laboratory in this context. HESS J1731-347 is a TeV source first seen in HESS galactic plane survey with unidentified counter- parts and later had a likely association with a SNR G353.6-0.7. So far there are only five SNRs which has significant resolved shell type morphology at gamma ray energies and HESS J1731-347 is the latest among them. This source is an ideal candidate to study the particle acceleration mechanism in SNR shocks. Studying the radio morphology of the remnant and constrain- ing the spectral index is crucial to understand the acceleration mechanism. We observe the remnant using Giant Metre Wave Radio Telescope (GMRT) and discover the 325 MHz and 610 MHz counterpart. This is the first detec- tion of G353.6-0.7 at these low frequencies. The complete shell is revealed in the GMRT map and we compare the resolved shell structure with the faint structures seen in other galactic plane surveys. We compare the GMRT maps with various dust maps and further confirm the likely association of HESS J1731-347 with the radio shell. The radio maps are compared with the HESS maps to see the correlation between high energy emission with radio emission. We find that the spectral index at the filaments are consistent with the non thermal feature as expected.

ASI 2016 – Abstract Book 74

SG-14 ASI2016_475 Kishalay De Poster

Gabriele Ponti (MPE, Garching), Teo Munoz-Darias (Instituto de Astrofisica de Canarias; Departamento de astrofisica, Univ. de La Laguna, Tenerife), Luigi Stella (INAF, Rome) and Kirpal Nandra (MPE, Garching).

The puzzling orbital period evolution of the LMXB AX J1745.6-2901

The orbital period evolution of X-ray binaries provides fundamental clues to understanding mechanisms of angular momentum loss from these systems. We present an X-ray eclipse timing analysis of the transient low mass X-ray binary AX J1745.6-2901. This system shows full eclipses and thus is one of the few objects for which accurate orbital evolution studies using this method can be carried out. We report on XMM Newton and ASCA observations covering 30 complete X-ray eclipses spanning an interval of more than 20 years. We improve the determination of the orbital period to a relative precision of 2 x 10^{-8}, two orders of magnitudes better than previous estimates. We determine, for the first time, a highly significant rate of decrease of the orbital period \dot{P}_{orb}=-4.03\pm0.32\times10^{-11}$~s/s. This is at least one order of magnitude larger than expected from conservative mass transfer and angular momentum losses due to gravitational waves and magnetic breaking, and might result from non-conservative mass transfer. Imprinted on the long term evolution of the orbit, we observe highly significant eclipse leads-delays of 10-20 s, characterised by a clear state dependence in which, on average, eclipses occur earlier during the hard state.

SG-15 ASI2016_476 HARIS U Poster

Jayant Murthy(2), and Ulysses J. Sofia(3) (2) Indian Institute of Astrophysics, II Block, Koramangala, Bangalore , Karnataka - 560 034, India (3) Department of Physics, American University, 4400 Massachusetts Avenue, NW, Washington, DC 20016

Interstellar abundances and depletions along Galactic sight line

The Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) has enhanced our understanding many aspects of interstellar medium of our galaxy. The wavelength coverage of FUSE ans HST is of great astrophysical importance. We use FUSE and HST data for interstellar abundances studies of some important atomic species, such as sulphur and silicon. We report the newly derived column densities by measuring the equivalent widths of several ultraviolet absorption lines. Comparisons of observed depletions and grain properties with existing dust models will be discussed.

ASI 2016 – Abstract Book 75

SG-16 ASI2016_518 Shantanu Rastogi Poster

Rashmi Singh, DDU Gorakhpur University

Study of astrophysically relevant phenyl substituted aromatic phenanthrene

Polycyclic Aromatic Hydrocarbons (PAHs) have been considered as an essential, ubiquitous species of the interstellar medium (ISM). PAHs are responsible for mid-IR emission bands that are most prominent at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.6 micron (3030, 1610, 1300, 1160, 890 and 790 cm-1). These bands are called Aromatic infrared bands (AIBs) because of aromatic nature of carrier molecules. The profile of these emission bands exhibit definite variations from source to source. The composite model spectra of mixtures of PAHs show uncertainty in matching the 6.2 micron feature. This emphasizes the need to consider a larger varieties of PAHs and PAH derivatives for simultaneous match of all AIBs. In this work, we illustrate the theoretical IR spectra of neutral and ionised PAH, phenanthrene substituted on the side with a phenyl group at different positions. The aim is to study their suitability, in terms of intensity, peak position and profile, for explaining the astrophysical AIBs. In particular, the optimized structures and vibrational spectra of 1-,2-,3-,4-, and 9- phenylphenanthrene are obtained using DFT/B3LYP functional in conjugation with 6-31Gd basis expansion. The moderation in the principle PAH features and additional bands that appear due to the phenyl group addition are studied. The feasibility of incorporating phenyl substituted PAHs in modelling astrophysical spectra is discussed.

SG-17 ASI2016_534 SATHYANARAYANAN Poster

Jayant Murthy (IIA, Banglore), Narayanankutty K (Amrita University, Kerala), Sujatha N.V (St. Xavier's College, Kerala)

Diffuse Ultra-Violet Radiation from Taurus Molecular Cloud

We analysed diffuse ultra-violet radiation from the Taurus Molecular cloud (TMC) at two different wavelengths (1500A, 2300A) with the latest Galaxy Evolution Explorer (GALEX) observations . We confirmed the observed anti correlation in the region between the diffuse radiation and the dust extinction by Hurwitz 1990; Lee et al. 2006 and Lim et al. 2013. As part of analyzing dust scattered radiation in this region, we studied dust distribution in TMC and observed that the Planck's reddening map (Planck Collaboration et al. 2011) is a better option over the most widely used Schlegel et al. 1998 map and the recently released 3D dust map by Green et al. 2015. Our Monte Carlo dust scattering code shows very little radiation originate behind the cloud. The total flux in the region is contributed by a number of stars and the level of scattered radiation is insensitive to the phase function asymmetry factor 'g'. We claim that the observed anti-correlation is not due to shadowing by thick molecular cloud, but purely coincidental.

ASI 2016 – Abstract Book 76

SG-18 ASI2016_549 Madhuri Gaikwad Poster

Madhuri Gaikwad (NCRA), Ishwara Chandra CH (NCRA) and Paula Benaglia (Insitituto Argentino de Radioastronomia)

GMRT Survey of Cygnus region.

Hundreds of gamma-ray detected sources go unidentified with no counterparts at any other wavelengths despite significant improvement in the sensitivity and resolution of high energy telescopes. Most of the identified sources emit at radio waves. The most accepted argument for this close relation between radio and VHE band is production of VHE emission through inverse Compton scattering by the same relativistic electrons responsible for radio emission. Existing major radio catalogs and surveys such as NVSS, FIRST and WENSS do not have sufficient angular resolution or sensitivity to uniquely identify counterpart for UNIDS. The northern-sky Cygnus region is extremely rich in stellar objects and contains many unidentified VHE sources, and there are no radio surveys with enough angular resolution and sensitivity to study the sources at the radio bands. In 2014, we initiated a GMRT survey at 325 and 610 MHz along the region, to find counterparts to high-energy sources through radio observations. We have completed the 325 MHz imaging of about 8 square degree region with rms noise of about 100 microJy and with an angular resolution of ~ 10 arcseconds. Here we present some of the results from the wide area survey of the region.

SG-19 ASI2016_555 Aishwarya Ashok Poster

Sujatha S M P Birla Institute of Fundamental Research

Fundamental parameters of the neglected open cluster Waterloo 1 in the galactic second quadrant

In this paper, we present the fundamental physical parameters of the not-so-well studied open cluster Waterloo1 located in the direction of Camelopardalis constellation. We have used the UBVRI CCD photometric data obtained through the LN2 cooled 2-m Himalayan Chandra Telescope and the near-infrared data in the JHK¬s filters acquired from the 2 Micron All Sky Survey. The radial extent of the cluster is found to be 3.5 arcmin. By way of plotting the regular two colour diagram (B-V) vs (U-B) the colour excess E (B-V) along the line of sight of the cluster is 0.95 mag. From the colour-magnitude diagrams, the distance and log (age) of the cluster have been estimated as 3.467 ± 0.5 kpc and 7.15 respectively indicating it to be a young enough cluster of solar metallicity, which could be chosen as a spiral arm tracer of the Galaxy.

ASI 2016 – Abstract Book 77

SG-20 ASI2016_562 Subhajeet Karmakar Poster

Jeewan C. Pandey, Aryabhatta Research Institute of observational Sciences (ARIES), Nainital Kuntal Misra, Aryabhatta Research Institute of observational Sciences (ARIES), Nainital

X-ray Superflare on CC Eri

We present an in-depth study of X-ray Superflare detected on an active binary system CC Eridani with the Swift telescope. The event triggered the Burst Alert Telescope (BAT) in the hard X-ray band on 2008 October 16 at 11:22:52 UT with X-ray luminosity of 5.54 x 10^{31} erg s^{−1}at 14-50 keV energy band - a superflare, by comparison with energies of typical stellar flares on active binary systems. The peak X-ray luminosity in 0.3-10 keV energy band reached to a value of 3.01 x 10^{32} erg s^{−1}, which is 792 times more than that of the quiescent state. Spectral analysis indicates a presence of three temperature corona with first two plasma temperatures remain constant during the flaring event at ~3 and ~10 MK. The flare temperature peaked at 139.3 MK, which is ∼ 3.5 times more than the quiescent level. The peak stellar abundances was derived to be 2.02 times more than solar abundances, which is also 7.2 times more than that of the quiescent abundance observed on CC Eri. The Emission Measure followed the flare light curve and peaked at a value of 12.73 × 10^{54} cm^{−2}, which is ∼ 1383 times more than the quiescent value. We derive a loop length of 5.6 $\pm$ 0.7 $\times$ 10$^10$ cm, which is an order larger than the previously observed largest flare on CC Eri. We also investigate the emission mechanism responsible for producing the 6.4 keV Kalpha feature which was clearly visible till 200 s from the peak of the superflare. This feature is difficult to interpret using the pure fluorescence hypothesis.

SG-21 ASI2016_564 Shylaja B S Poster

Venketeshwara Pai R School of EEE, SASTRA University, Thanjavur - 613401

Star Catalogue from texts on Indian Astronomy

It is well known that the 27 nakshatra system was used in India for the purpose of fixing the positions of the sun, moon and the planets. After several attempts these 27 stars have been identified in the sky though there is some ambiguity on the fainter ones. Here we have compiled all the bright stars listed in various texts; Suryasiddhantha onwards up to Siddhantha Darpana of Chandrashekhara Samantha totalling to about 100. The study reveals that a scale similar to the magnitude scale of brightness also was in vogue. The coordinates listed along with the stars help in fixing the epoch; the names like “Yesu nakshatram” reveal the influence of Arabic and European texts. The names used by fishermen, not listed in the Sanskrit texts are also included in the compilation.

ASI 2016 – Abstract Book 78

SG-22 ASI2016_574 Prasun Dhang Poster

Co -Authors: 1. Prateek Sharma(IISc) 2. Banibrata Mukhopadhyay(IISc)

Dichotomy between Black Hole and Neutron Star Accretion: Effect of Hard Surface

Estimates of accretion rate on to compact objects have been explored based on the well-known, spherically symmetric, inviscid, steady-state solution given by Bondi. This solution assumes that there is a sink of mass at the center - which in case of a black hole (BH) corresponds to the advection of matter across the event horizon. Other stars, such as a neutron star (NS), have surfaces and hence the infalling matter has to come to rest at the surface. We study the initial value problem in which the matter distribution is uniform and at rest at t=0 with two different inner radial boundary conditions: outflow boundary condition valid for a BH; and a reflective boundary condition for a NS. We obtain a similarity solution for the flow in the two cases (assuming a cold ambient medium) and compare with numerical simulations of the Euler equations. Numerical simulations show that spherical accretion on to NSs, and hence the energy released due to accretion, can be suppressed by orders of magnitude compared to BHs. These differences should be reflected in the observed luminosities of NS transient and BH transients when they are in quiescent states.

SG-23 ASI2016_582 neelam panwar Poster

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Low-mass young stellar content of the cluster IC1805

The W4 is a giant HII region ionized by more than 15~OB stars of the cluster IC~1805. It is an excellent laboratory for studying the feedback effect of massive stars on the surrounding material. However, the low- mass stellar content of the IC~1805 cluster remained very poorly studied till now. With the aim to unravel the low-mass stellar population of the cluster, deep optical data obtained with the Canada-France-Hawaii Telescope, infrared data from $Spitzer$ Space Telescope and X-ray data from Chandra Space Observatory have been used. We identified $\sim$ 500 young stellar objects (YSOs), thereby improving the YSO statistics of the cluster compared to the previous observations. These identified YSOs help us determine the age of the cluster which seems to be in the range of 0.1 - 5 Myr, with a mean age of $\sim$ 2.5 Myr. The mass-function of our YSO sample is close to the Saltpeter value; consistent with those YSO mass-function of massive star- forming complexes. We found that the diskless sources are relatively older when compared to disk bearing YSO candidates. The spatial distribution of YSOs, and the distribution of gas and dust of the complex indicate that IC 1805 could have formed in a filamentary cloud.

ASI 2016 – Abstract Book 79

SG-24 ASI2016_615 Richa Kundu Poster

Richa Kundu, Harinder P. Singh, Shashi M. Kanbur.

Examining empirical metallicity-Fourier parameter relations for RR Lyrae stars

RR Lyrae stars are tracers for the old stellar populations present in various environments. They are quite numerous. They have characteristic light curves which are relatively easy to observe due to their short periods and large amplitudes. They are useful in determining the galactic and extragalactic distances and for studying the structure of the Milky Way and other galaxies. RR Lyrae variables are radially pulsating horizontal branch stars, with periods in the range of 0.2–1.0 d and are classified into three main types according to the mode in which they pulsate: fundamental-mode RRab stars, first-overtone RRc stars and double-mode RRd stars.Determination of spectroscopic metallicities for these stars is expensive. Attempts have, therefore, been made to determine metallicities of RRab stars by relating these with the light curve structure through the Fourier parameters (Jurcsik & Kovacs, 1996; Nemec et al. 2013). We examine these empirical relations by using archival photometric and spectroscopic data.

SG-25 ASI2016_625 Nazma Islam Poster

Biswajit Paul, Raman Research Institute, Bangalore

Orbital evolution and search for eccentricity and apsidal motion in the eclipsing HMXB 4U 1700-37

In the absence of detectable pulsations in the eclipsing High Mass X-ray binary 4U 1700--37, the orbital period decay is necessarily determined from the eclipse timing measurements. We have used the earlier reported mid- eclipse time measurements of 4U 1700--37 together with new measurements from long term light curves obtained with the all sky monitors RXTE-ASM, Swift-BAT and MAXI-GSC, as well as observations with RXTE-PCA, to measure the long term orbital evolution of the binary. The orbital period decay rate of the system is estimated to be ${\dot{P}}/P = -(4.7 \pm 1.9) \times 10^{-7}$ yr$^{-1}$, smaller compared to its previous estimates. We have also used the mid-eclipse times and the eclipse duration measurements obtained from 10 years long X-ray light curve obtained with Swift-BAT to separately put constraints on the eccentricity of the binary system and attempted to measure any apsidal motion. For a reasonable rate of apsidal motion for this binary system, the eccentricity is found to be less than 0.008, which limits our ability to determine the apsidal motion rate from the current data. We discuss the discrepancy of the current limit of eccentricity with the earlier reported values from radial velocity measurements of the companion star.

ASI 2016 – Abstract Book 80

SG-26 ASI2016_634 GAUTAM SAIKIA Poster

Gautam Saikia, Tezpur University, Assam. Dr. P. Shalima, Regional Institute of Education Mysore, Karnataka. Dr. Rupjyoti Gogoi, Tezpur University, Assam.

Probing the source of FUV diffuse emission in Orion

Dust scattering is the main source of diffuse emission in the Far Ultraviolet (FUV). For several locations near M42, Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has observed diffuse radiation in the FUV as scattering of starlight from the Trapezium stars by dust in front of the nebula. The dust grains are known to be anomalous in Orion with RV = 5.5 and these are the first measurements of the FUV optical properties of the grains outside of “normal” Milky Way dust. Infrared (IR) emission features at 8 micron are generally attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules, while emission at 24 micron are attributed to Very Small Grains (VSGs). We compare the FUV diffuse emission with the mid-infrared (IR) and far-IR diffuse emission observed by the Spitzer Space Telescope (SST) and the Akari satellite for the same locations. The intensity ratios in the different mid-IR and far-IR bands for each of the locations will enable us to determine the type of dust contributing to the diffuse emission as well as to derive a more accurate 3D distribution of stars and dust in the region. This, in turn, may be used to model the FUV scattering in the Orion nebula.

ASI 2016 – Abstract Book 81

SG-27 ASI2016_636 MRIDUSMITA BURAGOHAIN Poster

Amit Pathak, Department of Physics Peter Sarre, The University of Nottingham

Vibrational spectra of deuterated PAHs: C-H out-of-plane vibrations

Mid-infrared emission lines popularly known as 'Aromatic Infrared Bands' are one of the most commonly observed features in the interstellar medium (ISM). Since its fist discovery in 1973, these bands have frequently been detected towards a diverse astrophysical source indicating its widespread presence in the ISM (Tielens 2008). Observations show prominent emissions lines at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 µm in the AIB spectrum whereas several minor bands are identified recently in the 3-20 µm regions. Three decades ago, Léger and Puget proposed Polycyclic Aromatic Hydrocarbon (PAH) molecules responsible for producing such emission lines in the ISM (Léger and Puget 1984). PAH molecules show IR spectra that are consistent with characteristic frequencies of the AIBs. According to the PAH-AIB hypothesis, an interstellar PAH molecule illuminates in IR due to the vibrational relaxation after absorbing a background UV photon (Allamandola et al. 1989). Despite the wide acceptance of the PAH-AIB hypothesis, identification of exact form of PAH molecules still faces major challenges. Extensive studies on PAHs, both laboratory and theoretical present a wide range of interstellar PAH family that strongly account for some of the observed bands, if not all. A recent study proposes PAH molecules with deuterium content (PADs) as AIB carrier that may explain the observed features in the 4-5 µm regions (Peeters et al. 2004). 11.2 µm features is one of the most distinctive band in the AIB spectrum and has been assigned to the C-H out of plane (OOP) bending mode in a neutal PAH that contains a solo C-H group (Hudgins & Allamandola 1999). This work reports a Density Functional Theory (DFT) study on PAH molecules with a solo C-D group to study the vibrational modes present in such molecules and to see the effect of deuteration on the 11.2 micron feature. DFT calculation has also been carried out for PAH molecules with duet, trio and quartet C-D groups to see the variations in the IR spectra. We present a detailed analysis of the IR spectra of these molecules and discuss the possible astrophysical implications. References: 1. Tielens, A. G. G. M., 2008, ARA&A, 46, 289. 2. L´eger, A. & Puget, J. L., 1984, A&A, 137, L5. 3. Allamandola, L. J., Tielens, A. G. G. M., & Barker, J. R., 1989, ApJS, 71, 733. 4. Peeters, E., Allamandola, L. J., Bauschlicher, Jr., C. W., Hudgins, D. M., Sandford, S. A., & Tielens, A. G. G. M., 2004, ApJ, 604, 252. 5. Hudgins, D. M. & Allamandola, L. J., 1999, ApJ, 516, L14.

SG-28 ASI2016_643 Dr. Umesh C Joshi Poster

U. C. Joshi, S. Ganesh., K. S. Baliyan Physical Research Laboratory, Ahmedabad INDIA

Polarimetry of R Aquarii - An Exploding Nearby Star

Abstract: R Aquarii is a nearby unique symbiotic star. The most notable observation is that R Aqr varies in brightness over the course of 387 days, going from an 11th magnitude star to a 6th magnitude star. Apart from this, it show peculiar polarization behaviour. Our earlier study on this source showed strong wavelength dependence of polarization and position angle which also showed strong time dependence. The variation in polarization in U-band was found to be much larger compared to that in longer wavelengths. To understand the long term polarization behaviour, we have been carrying out polarimetry on this source since 1995 from Mt Abu IR Observatory, India. Details on the polarization behaviour of this peculiar star will be presented.

ASI 2016 – Abstract Book 82

SG-29 ASI2016_657 Bari Maqbool Poster

1. Ranjeev Misra, IUCAA, Pune 2. Naseer Iqbal, Kashmir University 3. Naveel Ahmad, Kashmir University

Time dependent spectrum of an X-ray irradiated accretion disc with stochastic perturbations

The X-rays emitted by the inner regions of the accretion disk induce structural changes in the outer regions of the disk. We study here how the effective temperature and hence the corresponding spectrum of the disk is altered by stochastic perturbations in the outer regions and thereby try to study the long term variability which has been observed in some X-ray binaries. We use a time dependent global hydrodynamic code to study the variations in the effective temperature of the disk in response to sinusoidal accretion rate perturbations introduced at different radii and with different time periods. To quantify the results, we calculate the root mean square effective temperature at different radii and the root mean square flux at different frequencies. We also calculate the time-lags in accretion rate, effective temperature and the different frequencies.

SG-30 ASI2016_679 Rahul Kumar Anand Poster

Shantanu Rastogi Department of Physics, D.D.U. Gorakhpur University, Gorakhpur - 273009 Brijesh Kumar ARIES, Manora Peak, Nainital (Uttarakhand) - 263002

Infrared emission bands in some late carbon stars and correlation with other archival data

Observations from space telescopes, particularly infrared telescopes (IRAS, ISO and Spitzer), indicate ubiquitous presence of the mid infrared emission features at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 µm in nebular spectra. These features are attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules pumped by background UV radiations and are popularly known as Aromatic Infrared Bands (AIBs). In order to understand the origin and variation of these features in different objects, a study is performed on late type stars: IRC+10216, NGC7027 and BD30°3639, which are well known for their mid-infrared excess. Analysis of the information available in archival data for these objects in different wavelength windows is made. Attempt is made to identify any correlation that may exist between the AIB features and other bands. IRC+10216, also known as CW Leonis, is a carbon-rich evolved star in the AGB phase and is one of the most prominent and best-studied near-infrared (NIR) sources in the sky. NGC7027 and BD30°3639 are planetary nebulae. Due to its proximity, NGC7027 has a high surface brightness at all wavelengths. It has a very rich atomic and molecular spectrum. BD30°3639 is an optically bright, round, highly symmetric low-excitation nebulae. The AIB features in these objects have been classified as close to „B‟ class feature, related to benign conditions, which are considered to be locations for PAH formation and evolution. Study of the HST and other Space Telescope archival data in visible and UV regions is also done for these objects. Understanding of variations in band features and their correlations can be related to the different chemistry of PAH formation and evolution in the circumstellar medium.

ASI 2016 – Abstract Book 83

SG-31 ASI2016_680 Malu S Poster

Malu S., Sriram, K. and Vivekananda Rao P., Department of Astronomy, Osmania University, Hyderabad

KP103285: A Low Mass Ratio Overcontact Binary System

Over contact binary systems are considered to be an extremely vital tool to understand many important astrophysical phenomena including merger, the underlying mechanisms of the stellar dynamo process and stellar evolution. Their light curves show totalities at their minima which is indicative of the fact that they are low mass ratio systems. These systems are short period binaries (< 0.8 days) that often show systematic period variations caused due to mass transfer from one component to the other. Another striking feature presented by these systems are their low angular momentum configuration which is possibly due to the presence of a third component. We present the R band photometric analysis and the period variation study of the contact binary system KP103285. The CCD photometric observations of this system were performed at the IGO 2m telescope located at Pune, during January 2015. Along with our obtained times of minima, we have also collected the times of minima for the system from Pepper et al (2008), the NSVS and ASAS databases for over a duration of 16 years. The R band photometric solution of the system was obtained using the Wilson-Devinney (W-D) code. The obtained solution suggests that this system has a low mass ratio of 0.16 and an inclination of ~89°. The O-C diagram shows a systematic period variation (parabolic in nature) which is indicative of mass transfer from the secondary to the primary component. A secular increase is observed in the period of the binary system at the rate of dP/dt ~ 0.0948 sec/yr. Residuals obtained after removing the parabolic term in the O-C diagram show a quasi sinusoidal variation of period ~ 10.94 years which has an amplitude of 0.0069 days. This could be an indication of the possible presence of a third body. Further observations can help in verifying and confirming the obtained result.

SG-32 ASI2016_682 NAFISA AFTAB Poster

NAZMA ISLAM [ RAMAN RESEARCH INSTITUTE, INDIAN INSTITUTE OF SCIENCE] BISWAJIT PAUL [RAMAN RESEARCH INSTITUTE]

Variability study of the High Mass X-ray binary IGR J18027–2016 with Swift–XRT

We report the results from pulsations and spectral analysis of a large number of observations of the HMXB pulsar IGR J18027–2016 with Swift–XRT, carried out at different orbital phases. We found a significant intensity variations in the system at different orbital phases, higher than the orbital intensity modulation. In some orbital phases, as seen in different XRT observations, the X-ray intensity is found to vary by a large factor, of about ∼50. In all the observations with sufficient number of source X-ray photons, pulsations have been detected around the reviously known pulse period of ∼140 sec, consistent with the source being a persistent pulsator. The pulse profiles, however, show a significant change from a double peaked pulse profiles in most cases to a singled peaked pulse profiles in some observations. The nature of the pulse profiles are found to be independent of the X-ray intensity. In some of the observations, a 6.4 keV Fe Kα emission line is detected with a high equivalent width (∼1 keV). The absorption column density is found to be large before and after the eclipse, consistent with most of it being due to the stellar wind of the companion star. Such X-ray intensity variations outside the X-ray eclipse and associated spectral properties indicates a variable accretion onto the neutron star, which could be caused by a clumpy nature of the stellar wind of the companion star.

ASI 2016 – Abstract Book 84

SG-33 ASI2016_701 Avrajit bandyopadhyay Poster

Ms Susmitha Rani Antony,IIA Dr. Sivarani Thirupathi , IIA Dr. Sunetra Giridhar, IIA

Metal poor weak-G-band stars in the halo and globular clusters: exploring the common origin

Despite the globular clusters being old stellar systems in the halo, their chemical abundances have many differences with those of the halo stars. Here we shall present the study of Weak G band stars in the Galactic halo and compare their properties with members of some Galactic globular clusters. Abundance inhomogeneities like C-N,O-Na and Mg-Al anti-correlation is observed in all massive globular clusters. Such peculiarities are rare among halo stars. This abundance peculiarity is one of the important tools for identifying stars in the halo that were born inside a globular cluster. To understand the connection between the Globular cluster and the Milkyway halo stars, high resolution spectra of stars with weak G band has been observed, using the newly commissioned Hanle Echelle spectrograph. Such carbon depleted stars are ideal candidates to test for the C-N anomaly observed in clusters and its possible origin using high resolution spectroscopy of bright halo stars.

SG-34 ASI2016_702 Prasanta Kumar Nayak Poster

A. Subramaniam (Indian Institute of Astrophysics, Bangalore), S. Choudhury (Indian Institute of Science), G. Indu (Indian Institute of Astrophysics, Bangalore), Ram Sagar (Indian Institute of Astrophysics, Bangalore) STUDY OF STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUDS USING OGLE III SURVEY DATA The Large Magellanic Cloud (LMC) is a neighbouring galaxy (d $\sim 50$ kpc) to the Milky Way. It hosts a large number star clusters which are ideal tools to study stellar evolution, star formation history, cluster formation and dissolution processes in the galaxy. The most recent catalogue of star clusters in the LMC is by Bica et al. (2008), in which they have listed the preliminary information (coordinates and sizes) for ~ 3000 clusters. Only $\sim$ 30 \% of these catalogued clusters have information about their parameters like reddening and age (Pietrzynsky and Udalski 2000, Glatt et al. 2010, Popescu et al. 2012). A large fraction of star clusters are thus either not well-studied or are unstudied due to shallow photometric depth. A more precise determination of cluster parameters of larger sample is required to understand the star and cluster formation history of the LMC. In an effort to fill this gap, we have used one of the recent, and relatively high spatial resolution and deep optical photometric survey, the Optical Gravitational Lensing Experiment (OGLE) III survey for the LMC. We identified and estimated the ages and reddenings of over 1000 star clusters in LMC, which includes $\sim$ 600 clusters whose ages and reddenings are estimated for the first time. In our study the ages of the clusters are found to be in the range, log(t)= 6.80 - 9.4 (6.6 Myr - 2.3 Gyr), with an uncertainty of ± 0.20, better than previous age estimations. The colour excess in (V - I) lie between 0.013 to 0.57. We shall present and discuss these preliminary results.

ASI 2016 – Abstract Book 85

SG-35 ASI2016_705 Snehalata Sahu Poster

Annapurni Subramaniam and Indian Institute of Astrophysics

Galactic Globular Clusters: Revealing the UV properties using GALEX and HST Observations

We have selected four globular clusters(GCs) NGC 1851, NGC 5466, M5 and M10 to study the UV properties of Blue Straggler stars (BSS) and Horizontal Branch Stars (HB). These clusters have unique horizontal Branch and differ in their BSS population. Since identification of BSS in GCs are hampered by crowding due to main- sequence stars and red giants, switching to UV wavelength helps in detecting BSS in the central regions. We present the UV color-magnitude diagrams (CMDs) of four clusters which is obtained by doing the PSF photometry on the GALEX FUV and NUV images. By combining these with HST ACS observations, we have obtained the color magnitude diagrams in FUV, NUV and V, for the first time. The comparison of the UV CMDs with optical CMDs shows a variety of horizontal branch and blue straggler morphologies.

SG-36 ASI2016_706 Supriyo Ghosh Poster

Supriyo Ghosh$^{1}$, Soumen Mondal$^{1}$, Ramkrishna Das$^{1}$, Ashok N. M.$^{2}$, Banerjee D. P. K.$^{2}$ \affil{$^{1}$ S. N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata-700 098, India \\$^{2}$Physical Research Laboratory, Navrangpura, Ahmedabad-380 009, India } Spectro-photometric Studies of MASTER Optical Transient J183012.04+093342.6 : a OH/IR star in the Constellation Ophiuchus We present here optical/near-IR photometric and spectroscopic observations of the MASTER bright optical Transient J183012.04+093342.6 - a OH/IR star, using the NICMOS-3 on the 1.2m IR Telescope at Mt. Abu, and HFOSC and TIRSPEC on the 2m Himalayan Chandra Telescope (HCT) at Hanle. The presence of atomic/molecular features like NaI, CaI, TiO, VO, CO overtone and water bands in optical/near-IR spectra signify that the object is a cool M-type star. We study the phase-dependent optical/near-IR spectral variability of the source and determined fundamental parameters like temperature, luminosity class at different variability phases. In this presentation, we shall discuss our spectro-photometric observations and results on this OH/IR star.

ASI 2016 – Abstract Book 86

SG-37 ASI2016_715 SOMNATH DUTTA Poster

Soumen Mondal - S. N. Bose National Centre for Basic Sciences, Kolkata, India S. Joshi - Aryabhatta Research Institute of Observational Sciences, Nainital India J. Jose - Kavli Institute for Astronomy and Astrophysics,Peking University, Yi He Yuan Lu 5, Haidian District, Beijing 100871, China R. Das - S. N. Bose National Centre for Basic Sciences, Kolkata, India S. Ghosh - S. N. Bose National Centre for Basic Sciences, Kolkata, India

A census of variable stars in the young cluster NGC 2282 from differential photometry

We report preliminary results of CCD {\it I} time series photometry of the young cluster NGC 2282 using two optical telescopes in India. The deep {\it I}-band ($\sim$ 20 mag) analysis enables us to probe the study of variability towards low-mass end of pre-main sequence (PMS) stars. The technique of differential photometry has been used to identify photometric variable stars, which provides high photometric precision, even in the central crowded nebulous region. Additionally, large rms deviation of magnitudes from normal trends and significant periods in a Lomb-Scargle analysis were also considered as signatures of variable stars. A total of 49 stars were found as photometric variable. The PMS members associated with the region were identified using infrared (IR) data from UKIDSS and {\it Spitzer}-IRAC. Based on the optical and NIR color-magnitude diagram analyses, the age of the probable PMS variable sources has been estimated to be in the range of 1$-$5 Myr. Masses of these PMS variable stars were found to be $\sim$ 0.15$-$3.0 M$_\odot$ and these could be T Tauri stars. Majority (85\%) of the variable T Tauri stars have periods less than 15 days, such periodic variability are proposed to be the results of rotational modulation by hot or cool stellar spots on the star surface.

SG-38 ASI2016_717 Anirban Bhowmick Poster

Dr. Gajendra Pandey, Associate Professor, IIA (Indian Institute of Astrophysics)

Determination of $^{16}O/^{18}O$ ratios in carbon rich hydrogen deficient stars from their infra-red spectra

The formation and evolutionary connections of carbon rich hydrogen deficient stars viz. R Coronae Borealis stars (RCBs), Hydrogen deficient Carbon stars (HdCs), DYPer and DYPer candidates are not clearly known. Till now two possible scenarios have been proposed for the formation and evolution of these stars: 1) Merging of two white dwarfs and 2) Final Helium shell flash in a post AGB (Asymptotic Giant Branch) star. Till date in some of the known RCB/HdC stars the $^{16}O/^{18}O$ ratios are observed to be very low whereas $^{16}O/^{18}O$ in the solar neighbourhood is $\sim$ 500. Thus the $^{16}O/^{18}O$ ratios are one of the potential clues for determining their formation and evolutionary scenario. Hence we observationally investigate low resolution (R $\sim$ 1200) H and K band spectras of a group of RCBs, HdCs and DYPer and DYPer candidates using TIRSPEC on HCT 2m telescope, Hanle, to look for the near IR transitions of CO and its isotopes for determining $^{16}O/^{18}O$ ratios.

ASI 2016 – Abstract Book 87

SG-39 ASI2016_721 Eeshan Hasan Poster

1.Eeshan Hasan, University of Hyderabad, Hyderabad 2. Priya Hasan, Maulana Azad National Urdu University, Hyderabad

Star Formation and its progress in Serpens

We present the results of a deep near-infrared imaging survey of the Serpens Cloud made with FLAMINGOS at the 2.1 m telescope at Kitt Peak National Observatory. We modify the algorithms used to identify clusters. The conventional Nearest Neighbor Method may exclude stars from the cluster edge. Hence we propose necessary modifications for the algorithm. We propose the use of a modified Nyquist box to calculate and represent cluster parameters as well. We study the distribution of young embedded sources using the nearest neighbor method applied to a carefully selected sample of near-infrared excess (NIRX) stars that trace the latest episode of star formation in the complex. Our analysis finds the existence of six clusters, of which three are new in the molecular cloud. The new cluster identified were verified using the UKIDSS data, was missed also by c2D. We study the distribution of Class 0/I, II and III sources in the cloud and using ratio maps study the progress of star formation in the cloud using Spitzer c2D data. We determine a median age for the cluster to be 1-2 Myr at a mean distance of 300 pc.We construct extinction maps for the Serpens star cluster. We study the overall star formation in Serpens by comparing the properties of individual clusters with those of the Rosette Cloud and others.

SG-40 ASI2016_731 HARIKRISHNA SRIPADA Poster

Sriram, K.

MERGER AT CRITICAL MASS RATIO IN CONTACT BINARIES

Theoretical studies indicate that contact binaries ultimately form rapidly rotating single-stars merging possibility at (critical mass ratio) q = 0.05-0.09. We accumulated a sample of 143 contact binaries with their mass-ratio, orbital period and filling factor in order to constrain the critical mass-ratio. Our studies show that the critical mass-ratio (q) lies at 0.02 which is much lower than the predicted one. We study the possible consequences of the observed critical mass ratio in the context of merger phenomenon.

ASI 2016 – Abstract Book 88

SG-41 ASI2016_740 Priya Hasan Poster

Scott Wolk^2, Hans Moritz Günther^3, S Thomas Megeath^2, R A Gutermuth^4 2. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 3. Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, NE83-557 Cambridge, MA 02139, USA 4. Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA

An Xray Survey of the Young Stellar Population of NGC 281

NGC 281 (the Pac Man Nebula) is a complex region of star formation. At a distance of about 2 kpc is lies a remarkable 300 pc above the galactic plane. It is generally divided into 2 subregions, east and west, based on the $^{12}$CO distribution (Elmegreen \& Lada 1978). In the western part of NGC 281, is a large bubble H\II~ region prominent features include a young open cluster of stars (IC 1590), and a large lane of obscuring gas and dust. To the east, along the ionization front is a smaller, less stressed, embedded cluster. The cloud seems to be under active stress from the H\II~ region. The Pac Man Nebula, NGC 281, was observed with Chandra for 100 ksec using the Advanced CCD Imaging Spectrometer (ACIS) supported by data from the Spitzer IRAC and MIPS instruments. NGC 281 was observed with Chandra in 2005 for almost 100 ks with the ACIS in three sets of observations. This work involves identification of point sources in NGC 281, photometry and spectroscopy of brighter sources to separate them from the diffuse emission. We find the Xray luminosity function and study its completeness and estimate the number of missing sources and their energy and energy distribution. We also use Spitzer data to study the Young Stellar Population and the spatial distribution of Class I, Class II and Class III sources.

SG-42 ASI2016_769 Gayathri Raman Poster

Author 1: Gayathri Raman, Raman Research Institute Author2: Chandreyee Maitra, IRFU CEA, Saclay, France Author 3: Biswajit Paul, Raman Research Institute

Timing and spectral studies of the dipping source XTE J1710-281

Timing and spectral studies of eclipsing and dipping Low Mass X-ray Binary (LMXBs) sources are useful to probe the structures in the accretion disk and the material surrounding it. Structures present on the accretion disk aroound compact objects lead to absorption signatures from many highly-ionized species and also neutral material that usually are responsible for the X-ray dips occurring at different orbital epochs. XTE J1710-281 is a transient Low Mass X-ray Binary (LMXB) with an inclination angle i ~75-80 degrees. It shows periodic X- ray eclipses every 3.28 hours. This LMXB also exhibits X-ray intensity dips that are phase-locked, indicative of obscuration by a thickened accretion disk at the outer regions. We have carried out a multi-mission timing and spectral study of this dipping source using Chandra and Suzaku archival data. We have obtained timing signatures that indicate the presence of accretion disk structures that may be evolving at orbital times-scales of a few hours. We also detect a number of interesting features in the Suzaku spectra. We also present the similarities and differences in the the timing and spectral properties of this source and another well-studied eclipsing source, EXO 0748-676.

ASI 2016 – Abstract Book 89

SG-43 ASI2016_795 Pankaj Sanwal Poster

Dr. Brijesh Kumar

Broad-band photometric survey of zenith sky at Nainital

We present preliminary results of a deep broadband photometric survey of zenith sky at latitude (29.4 deg) of Nainital. The aim of the survey is to generate fainter standard stars in the 30 arcmin strip of the zenith sky. This data can be used for a wide variety of astronomical topics as well as technical characterization of telescope and instruments. This limited zenith sky survey is being done at broad-band VRI filters using 1k x 1k CCD mounted with the 104-cm telescope, the work involves observation-calibration of the photometric images, classification of objects (point source and extended source), the sensitivity determination of zenith sky and preparation of a unique standard catalog. In this contribution, we describe strategy for this survey.

SG-44 ASI2016_805 Abhisek Mohapatra Poster

Ananta C. Pradhan (National Institute of Technology, Rourkela, Odisha 769008, India) D. K. Ojha (Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India) A. C. Robin (Institut Utinam, CNRS UMR 6213, Universite de Franche-Comte, France) S. K. Ghosh (National Centre for Radio Astrophysics, Pune 411007, India)

Study of Structure of Our Galaxy Using Ultra-violet Star Counts of GALEX Survey.

We have analyzed the entire GALEX catalog to identify the UV stellar point sources by using the IR colour cut method (J-W1 < 1.2, W1 is a WISE band at 3.4 micron and J is a 2MASS band) (Pradhan et al. 2014). We compared the observed star counts with Besancon model of stellar population synthesis. We then identified the white dwarf candidates (WDs) of the disk and blue horizontal branch star candidates (BHBs) of halo from the observed sample by selecting suitable UV colour (FUV - NUV) ranges. We have produced catalogs and made quantitative estimates of the space densities of these objects in our Galaxy. The Besancon model has also been developed to predict star counts in the UV passbands of the UVIT which will be very useful to separate out different stellar populations and to estimate the structural parameters of the Galaxy with better precision.

ASI 2016 – Abstract Book 90

SG-45 ASI2016_815 Susmita Das Poster

Susmita Das(Department of Physics & Astrophysics, University of Delhi, Delhi 110007, India.) Anupam Bhardwaj(Department of Physics & Astrophysics, University of Delhi, Delhi 110007, India.) Shashi M. Kanbur (State University of New York, Oswego, NY 13126, USA.) Marcella Marconi(INAF-Osservatorio astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy) Harinder P. Singh (Department of Physics & Astrophysics, University of Delhi, Delhi 110007, India.)

Multi-wavelength Analysis of Theoretical light curves of RR Lyrae

We present an analysis of the theoretical light curves of the fundamental and first-overtone mode RR Lyrae variables using the Fourier decomposition technique. The light curves were adopted from nonlinear, time- dependent convective hydrodynamical pulsation models of RR Lyraes for a wide range of the metal abundances (metal-poor Z=0.0001 to solar metal abundance Z=0.02) in the optical (UBVRI) and near- infrared(JKL) bands. We determined the variation of Fourier Parameters as a function of period, wavelength and metallicity. We find that Fourier amplitude parameters decrease as function of wavelength while Fourier phase parameters increase with wavelength for a given period. We observe a distinct separation in the pattern around 0.6 days in most of the Fourier parameters as a function of period at multiple wavelengths. We also analysed the Period-Color and Amplitude-Color relations for RR Lyraes as function of pulsation phase and period over different wavelength and metallicities. The P-C relation for RR Lyrae at minimum light is flat at multiple wavelengths and is consistent with observed P-C relation in Bhardwaj et al. (2014). The P-C and A-C relations also provide evidence of a linear dependence on the metal abundance and are consistent with the theoretical explanation based on the stellar photosphere and the hydrogen ionization front.

ASI 2016 – Abstract Book 91

SG-46 ASI2016_819 Devansh Agarwal Poster

Devansh Agarwal (IISER-Thiruvananthapuram), Kishalay De (IISc-Bangalore) and Yashwant Gupta (NCRA- TIFR, Pune)

Multi-frequency profile evolution of Millisecond Pulsars

Though Millisecond Pulsars (MSPs) differ significantly from normal pulsars in periods, period derivatives, magnetic field strengths and evolutionary history, there are interesting comparisons in their emission properties. In particular, it is instructive to compare pulse profiles and their evolution with observing frequency. Kramer et al. (1998) did the first and to date the most comprehensive study of the frequency evolution of MSPs with a sample of 18 objects. However, very low-frequency observations were not included in this study. The high sensitivity of the GMRT at low frequencies makes it the ideal instrument to probe aspects of millisecond pulsar emission in this regime, and extend the existing database of MSP profiles to lower frequencies. We present results from a comprehensive study of 40 MSPs to investigate the frequency evolution of their profiles. We used existing data from the GMRT, along with the newly developed coherent dedispersion pipeline, to observe these MSPs at 2 to 4 frequency bands and constructed their average profiles. Subsequently, the average profiles were collated with existing profiles available in the EPN pulsar database and the literature, to assemble an extensive data set of MSP profiles over a broad range of frequencies. The profiles were aligned, normalised, and stacked for comparison. To quantifying the evolution of profiles with observing frequency, their widths ($w_{50}$) and peak to peak component separation (for multi-component) MSPs were calculated as a function of radio frequency. The standard radius to frequency mapping model (Cordes 1978) for normal pulsars describes that the profiles become wider, and separation between individual emission components increases. In this paper, we show that the RFM model does not apply very significantly to MSPs. We show few cases where the component separation increases (or increases and then saturates) with increasing frequency. Such deviations might be able to reveal interesting facts about the emission mechanism of these pulsars, and we discuss possible implications of these.

ASI 2016 – Abstract Book 92

SG-47 ASI2016_833 Nagendra Kumar Poster

Prof. Ranjeev Misra

Inferring the possible geometry of the Comptonizing system in NS LMXBs & Time-lags associated to Comptonization process, a Monte Carlo study. The observed soft lags of kHZ QPOs in neutron star (NS) low-mass X-ray binaries (LMXBs) is explained, generally, in thermal Comptonization (TC) model when one consider the affect of some fraction of Comptonized photons ($\eta_e$) which impinge back to the source. This fraction depends naturally on the geometry of the system and this involves, tracing photons as the scatter in space. A Monte Carlo (MC) method is developed for the thermal Comptonization process. We computed the fraction $\eta_e$ for different geometries as well the fraction of photons which will impinge back on the accretion disk $\eta_{irr}$. Three geometries were considered: (i) where the corona is a spherical shell covering the input source along with the possibility that there is a gap between the two i.e. a hollow shell, (ii) where the corona is in the form of a boundary layer and (iii) where the corona exists above the accretion disk. We find that the $\eta_e$ obtained from these geometries roughly correspond to the constraints obtained in the TC models for the first two geometries. In Comptonization, the high energetic photons is generally scattered more comparison to softer ones, so the “hard lag” should be observed. The observed both type of lag `hard' & 'soft' lag associated to X- ray variability are explained due to oscillations in temperature either of seed-photon source ($T_b$), or medium ($T_e$), or combination of them, in TC model. These lags can be explained in a MC methods. We find that when a less then half cycle of temperature is changed during photons crossing time, the lag is hard lag and for more then half cycle the lag is soft.

SG-48 ASI2016_904 Sneh Lata Poster

A. K. Pandey (ARIES), Neelam Panwar (DU), W. P. Chen (IANCU, Taiwan), M. R. Samal (AMULAM, France), J. C. Pandey (ARIES)

Variable stars in young open star cluster NGC 7380

We present time series photometry of 57 variable stars in the cluster region NGC 7380. The membership of these variable stars to the cluster NGC 7380 has been established on the basis of two colour diagrams and colour-magnitude diagrams. Seventeen stars are found to be main-sequence variables, which are mainly B type stars and are classified as slowly pulsating B stars, β Cep or δ Scuti stars. Some of them may belong to new class variables as discussed by Mowlavi et al. (2013) and Lata et al. (2014). Present sample also contains 14 pre-main-sequence stars, whose ages and masses are found to be mostly ≲ 5 Myr and range 0.60 ≲M/M⊙≲ 2.30 and hence should be T-Tauri stars. About half of the weak line T-Tauri stars are found to be fast rotators with a period of ≲ 2 days as compared to the classical T-Tauri stars. We have also detected some of the variables belonging to the field star population.

ASI 2016 – Abstract Book 93

SG-49 ASI2016_929 Ekta Sharma Poster

Dr.Maheswar Gopinanthan(ARIES),Dr.Archana Soam, Neha Sharma, Piyali Saha (ARIES)

Optical polarimetry towards L1157 molecular cloud

In this work, we present the preliminary study of the optical polarisation measurements of the stars projected on L1157 molecular cloud which contains a low mass class 0 protostar associated with the prominent bipolar outflows. Light from the stars, while passing through the dust grains that are aligned with their minor axis parallel to the external magnetic fields, gets linearly polarised. Polarisation measurements in the optical wavelength can trace the plane-of-sky component of the magnetic field in the core envelope. It has been widely accepted that the magnetic fields play an important role in the spontaneous star formation process. In a magnetic field dominated scenario for isolated low mass star formation, outflow axis is considered as the proxy of the rotation axis of the core. With the help of the optical polarisation study by us (in the cloud envelope) and the literature available on the sub-mm polarisation measurements (in the cloud core) in the vicinity of the outflow, we will examine how the magnetic field morphologies are correlated to the outflows and the flattened structure right from the core to the envelope of L1157. Our preliminary results towards this cloud will be discussed in this poster at ASI.

SG-50 ASI2016_946 Sarmistha Banik Poster

1.Krishna Prakash Nunna BITS Pilani Hyderabad Campus 2. Prasanta Char Saha Institute of Nulcear Physics, Kolkata

Deformation properties of rotating neutron stars with exotic equation of state with density dependent couplings

Pulsars are rotating neutron stars with period ranging from seconds to sub -milliseconds. A small degree of asymmetry arises as a consequence of their rapid rotation. This asymmetry in the spherical mass distribution, in turn creates a distortion in the gravitational field outside the star [1]. The moment of inertia (I), rotational to gravitational energy ratio (T/|W|) and quadrupole moment tensor (υ) are some of the parameters that lead to explore the deformation properties of the neutron stars. The exceptionally dense cores of neutron stars led scientists to believe that apart from neutrons, protons and electrons, these stars are also composed of other sub- atomic strange particles such as hyperons, pion and kaon condensates [2]. Usually, the strangeness degree of freedom softens the Equation of state (EoS), lowering the maximum mass of the compact stars. However, it was shown in Ref [3], that the DD2 models[4] have scope to accommodate strange hyperons and anti-kaon condensates within the observational mass limit. We consider a phase transition from hadronic to anti-kaon condensed matter and study its effect on the bulk properties such as quadrupole moment, moment of inertia and the ratio of rotational energy to gravitational energy for the rotating neutron stars. References: 1.N. Stergioulas, Living Review, 6 (2003), 3. 2. N.K. Glendenning, Compact stars, (Springer, New York, 1997). 3.P. Char, & S. Banik. Phy RevC, 90, 015801 (2014). 4.S. Typel and H. H. Wolter, Nucl. Phys. A656, 331 (1999).

ASI 2016 – Abstract Book 94

SG-51 ASI2016_951 Siddhartha Gupta Poster

Siddhartha Gupta(1,2), Biman B. Nath(1), Prateek Sharma(2), Yuri Shchekinov(3); (1) Raman Research Institute, Bangalore, India (2) Indian Institute of Science, Bangalore, India (3) P. N. Lebedev Physical Institute, Moscow, Russia

Effect of radiation pressure on superbubbles in dense medium

Feedback mechanisms are crucial in understanding the evolution of galaxies. A large contribution of such feedback comes from superbubbles that are driven by massive young star clusters. Using hydrodynamic simulations, we study the role of radiation pressure on the dynamics of superbubbles. We show that the concept of the cooling time scale of the shocked wind region estimated from the adiabatic model is not applicable in dense medium (density greater than ~100 mH/cc) and can bring different conclusions in understanding the role of driving mechanisms. We also show that the effect of radiation pressure may be dynamically important in pushing out the surrounding gas at the early stages of bubble evolution. We compare our results with the giant HII region 30 Doradus in Large Magellanic Cloud, and conclude that the radiation pressure might have a significant role at the early stage (< 2 Myr) of its evolution.

SG-52 ASI2016_956 Indulekha Kavila Poster

Anu Babu, School of Pure & Applied Physics, Mahatma Gandhi University, P D Hills PO, Kottayam 686560 KERALA

Implications of Star Cluster Formation Scenarios for the IMF

The stellar Initial Mass Function (IMF) is an important input into our study of the universe, the low mass end contributing long lived, low luminosity objects to their parent galaxies and massive stars leading short but spectacular lives, producing large and lasting changes in their environments, driving evolution. The universality or otherwise of the IMF is a hotly debated question which gives varying answers between ddifferent samples and different locations. The IMF shows the following general feature - a rise from the lower masses changing, beyond a turnover, into a drop best fitted by a power law, at the high mass end. Universality is proscribed for the IMF on the grounds of the scale-free nature of the physical processes that are thought to be decisive in the process of star formation -viz turbulence and gravity. Explorations of turbulent fragmentation scenarios also do produce results that share some universal features -like a Salpeter like slope at the high mass end and a turnover mass that is seen to be dependent on the Jeans' mass of the system. Given the observations and the results of various analyses of the IMF, we examine the implications of various scenarios for the formation of bound stellar clusters (like a density dependent Star Formation Efficiency for example) for the nature of the IMF.

ASI 2016 – Abstract Book 95

SG-53 ASI2016_957 Subhashis Roy Poster

Sabyasachi Pal (ICSP)

Nature of a transient source near Galactic centre

From our observations of a region about a degree away from the Galactic Centre with the GMRT about a decade back, we report discovery of a small angular sized source which has been found to be in the on and off state in time scale of a few years. This object G359.1+1.0 is seen within the supernova remnant G359.1+0.9. From our 325 and 610 MHz observation with the GMRT, its spectral index is found to be steep. Its measured value is -0.9 +/- 0.2. Its flux density at 325 MHz is about 50 mJy and is extended along North-South with an angular size of 30"x10". However, this source is undetected in the NRAO VLA sky survey (NVSS) at 1.4 GHz, the observation for which was sometime between 1993-1996 implying the source was more than a factor of 5 fainter than expected based on its metre wavelength spectral index. From the archival Very Large Array data, this source was not detected in 1984 at 1.6 GHz, but is detected in October 1990 at the same frequency. From these observations, we find the shortest variability timescale of about 5 years. Equating it to the ratio of source size to the velocity of light, indicates the object is of size about 1 pc. Considering its angular size, the distance of this object is ~11 kpc, indicating it to be Galactic in origin. We argue that this object is unlikely to be a pulsar, pulsar wind nebula, radio star, Herbig-Haro object or part of any supernova remnant. This source could be a newly detected microquasar.

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ASI 2016 – Abstract Book 96

ASI-2016 Poster Presentations

General Relativity and Cosmology

GRC-1 ASI2016_1012 N. Udaya Shankar Poster

Mayuri Sathyanarayana Rao (Raman Research Institute, Bangalore & Australian National University, Canberra) Ravi Subrahmanyan (Raman Research Institute, Bangalore), N Udaya Shankar (Raman Research Institute, Bangalore), Jens Chluba (Kavli Institute for Cosmology, Cambridge)

Modeling the Radio Foreground for detection of spectral distortions from the Epoch of Reionization

Cosmological Reionization results in additive spectral features in the cosmic microwave background (CMB) at low frequencies. A detection of these spectral features arising from the Epoch Of Reionization or EoR ($30\lesssim z \lesssim 6$) would provide clues to the thermal history of the baryons and the nature and timing of the first collapsed objects. There are global, all-sky isotropic spectral features as well as angular variations in spectral structure, embedded as tiny additive components in the radio background. Galactic and Extragalactic radio emission is the dominant foreground in the radio band; together with the CMB these are orders of magnitude brighter than the EoR signatures. Therefore, detection requires methods for precise modeling of foregrounds. Since telescope beams average over foreground sources along line of sight and over beam area, and foreground radio sources have a spread in their emission spectral indices, the functional form for the foreground detected by telescope beams is a priori unknown. Conventional methods adopt polynomial forms of higher orders for modeling foregrounds with greater accuracy, inevitably confusing the foreground with the embedded weak EoR signatures. Here we investigate the radio foreground for the global EoR signal and present a physically motivated sky-model. Using this sky-model we generate synthetic sky-spectra as observed by an ideal instrument and investigates methods to detect the global EoR signal, distinguishing it from the bright foreground, without compromising signal integrity. We also provide results of statistical tests on the simulated sky-spectra to determine the confidence in detection of the global EoR signal with various methods of foreground subtraction.

GRC-2 ASI2016_395 Ophelia Fabre Poster

J.Kovoor, S.Shankaranarayanan

Signature of primordial magnetic fields in the CMB with Faraday rotation

The origin of large coherence-length magnetic fields in the Universe remains currently unknown. Different mechanisms have been proposed to explain them, and we focus here on seed magnetic fields produced in the early Universe, and then amplified by dynamo effect in galaxies. We show that the Cosmic Microwave Background (CMB) polarization is efficient to constrain these primordial magnetic fields thanks to Faraday rotation. Faraday rotation is the modification of the polarization of an incoming electro-magnetic wave in a medium where free electrons and a magnetic field are already present. We present different models of primordial magnetic fields and their characteristic Faraday rotation signatures in the CMB power spectra. We finally discuss their detectability with regards to Planck data.

ASI 2016 – Abstract Book 97

GRC-3 ASI2016_398 Soham Bhattacharyya Poster

Dr. S Shankaranarayanan HoD, SOP IISER TVM

Investigation of scalar hair in f(R) black holes using numerical techniques

The debate about the presence (or absence) of scalar hair has been going on for long. Uniqueness theorems, Birkhoff's theorem, Bekensteins' V theorem all showed that a static, asymptotically flat black hole solution in G.R. cannot have scalar hair. Hence f(R) theories have become a testing ground for the no scalar hair hypothesis. f(R) vacuum perturbations have two tensor and one scalar mode of freedom. Upon a suitable conformal transformation of the metric it is possible to decouple the scalar degree of freedom into a scalar field with a potential. Numerical simulations make it possible to solve the dynamical conformally transformed field equations. As a simple case we let a massless scalar field collapse in a spherically symmetric spacetime and observe the values of this scalar field at different time and distances. We also investigate the black hole horizon formation around the time and place it starts to form. This study provides us with clues as to whether we can detect scalar modes of gravitational waves in GW detectors.

GRC-4 ASI2016_468 Reju Sam John Poster

Surajit Paul, Dept. of Physics, University of Pune and Associate faculty IUCAA, Pune Luigi Iapichino, Zentrum fur Astronomie der Universitat Wurzburg, Institut fur Theoretische Harish Kumar, Dept. of Physics, PEC, Pondicherry University

Manufacturing cosmic rays in the evolving dynamical states of Galaxy clusters

Galaxy clusters are the biggest object that evolved through continuous accretion and violent mergers. These mergers are the known most energetic event in this universe with an energy release of as high as $10^{64}$ ergs. Such events are thus capable of pumping up the energy of the particles present in the ambient medium through Diffusive Shock Acceleration (DSA) and fills the Intracluster Medium (ICM) with energetic cosmic rays (CRs). But, such acceleration doesn't happen through out the merging process that spans to almost 4 Giga years. Our study reveals that such conversion of thermal to non-thermal CR acceleration takes place at certain dynamical state. For this purpose, using virial theorem as the yard stick, we have divided the whole merging process in to three distinct dynamical states and observed that only state i.e. when the system starts dominating by kinetic energy, Cosmic Ray production suddenly shoots up creating a flashing moment. Such state stays only for a Giga year or so and makes it difficult for observer to pin point such moments. Structure formation being a many body problem, are best studied numerically. For this study we thus modelled the Galaxy cluster formation using ENZO Dark Matter plus hydrodynamic code with millions of particles and additional heating and cooling physics to make it more realistic. In this work, for the first time we also reveal distinct scaling laws for mass and CR luminosity for merging and non-merging systems. We will also discus a unique method to determine the dynamical state of any Galaxy clusters using some easily observable segregation parameters.

ASI 2016 – Abstract Book 98

GRC-5 ASI2016_482 Priyanka Singh Poster

Sandeep Rana, IISER, Mohali. Jasjeet S. Bagla, IISER, Mohali. Biman B. Nath, RRI, Bangalore

Suppression of galactic outflows by cosmological infall/circumgalactic medium

Galaxies undergo feedback processes such as supernovae and active galactic nuclei giving rise to outflows carrying metal enriched gas into the galactic halo and intergalactic medium (IGM). At the same time, galaxies accrete matter from the IGM. We study the suppression of outflow velocity by the infalling gas. The reduction in the outflow velocity due to the infall depends on the mass and redshift of the galaxy. We find that in the presence of infall, the upper mass limit beyond which there are no outflows, decreases approximately by a factor of two, independent of the redshift of the galaxy. In addition to infall, the existence of hot circumgalactic medium (CGM) in massive galaxies also decelerates the outflows. Together, infall and the hot CGM give a mass limit separating the galaxies with and without unsuppressed outflows. We investigate the relative importance of these two outflow suppression processes as a function of redshift and discuss their impact on the enrichment history of the galaxy and its environment.

GRC-6 ASI2016_495 Anirban Ain Poster

Sanjit Mitra, IUCAA

Fast Mapping of Stochastic Gravitational Wave Background Using Data Folding

Gravitational Waves (GW) are propagating distortions of spacetime predicted in Einstein‟s general theory of relativity. Various types of sources are expected to emit GWs of different frequencies and durations, which may contain important astrophysical information not accessible to traditional electro-magnetic astronomy. A stochastic GW background (SGWB) is one such source created by a large number of unresolved astrophysical sources and phenomena in the early universe like cosmic inflation. Probing an anisotropic SGWB is best achieved by employing the GW radiometer algorithm using ground-based interferometric detectors. It maps the GW sky using cross-correlation of data from pairs of detectors. Exploiting a temporal symmetry in the radiometer algorithm we have developed and implemented a technique to fold cross-spectral data for the whole observation period to only one sidereal day without any loss of precision. Folding thus makes data analysis more than two orders faster, making it possible to perform searches which have been computationally prohibitive. Being only about a gigabyte in size, folded data offers enormous portability and convenience in handling. Folding incorporates most of the details involved in preprocessing, alleviating many dirty steps otherwise involved in the main analysis. In summary, folding has enabled us to perform a full fledged search for an SGWB on a laptop computer!

ASI 2016 – Abstract Book 99

GRC-7 ASI2016_509 Raghunath Ghara Poster

Tirthankar Roy Choudhury (NCRA-TIFR, Pune), Kanan K. Datta (Presidency University, Kolkata)

21-cm signature of the first sources in the Universe: Prospects of detection with SKA

Currently several low-frequency experiments are being planned to study the nature of the first stars using the redshifted 21-cm signal from the cosmic dawn and epoch of reionization. Using a one-dimensional radiative transfer code, we model the 21-cm signal pattern around the early sources for different source models, i.e., the metal-free Population III (PopIII) stars, primordial galaxies consisting of Population II (PopII) stars, mini- QSOs and high-mass X-ray binaries (HMXBs). We investigate the detectability of these sources by comparing the 21-cm visibility signal with the system noise appropriate for a telescope like the SKA1-low. Upon integrating the vis- ibility around a typical source over all baselines and over a frequency interval of 16 MHz, we find that it will be possible make a ∼ 9 − σ detection of the isolated sources like PopII galaxies, mini-QSOs and HMXBs at z ∼ 15 with the SKA1-low in 1000 hours. The exact value of the signal to noise ratio (SNR) will depend on the source properties, in particular on the mass and age of the source and the escape fraction of ionizing photons. The predicted SNR decreases with increasing redshift. We provide simple scaling laws to estimate the SNR for different values of the parameters which characterize the source and the surrounding medium. These calculations will be useful in planning 21-cm observations to detect the first sources.

GRC-8 ASI2016_520 nomaan Poster

Sumati surya and Raman Research Institute

Some Ideas in Causal set Quantum Gravity

Using the causal set theory, an expression for the propagator for a massive KG field inside a small causal diamond in (1+1) dimensions in curved spacetime is obtained. This propagator is shown to match exactly with the corresponding continuum case in the appropriate limit. The idea of an covariant definition of a vacuum (called the SJ vacuum) is presented and applied to the above case.

GRC-9 ASI2016_579 KINJALK LOCHAN Poster

Suratna Das (IIT Kanpur), Angelo Bassi (University of Trieste)

Constrainting Quantum theory from CMBR and Standard Cosmology

Modification of quantum theory is motivated from various theoretical/phenomenological considerations. Typically such modifications are tuned such that they survive experimental scrutiny in labs. However, cosmology provides another arena to study and constraint the parameters of such distortions. We will discuss certain modified quantum theories and constraints from considering several cosmological scenarios like evolution of CMBR, expansion history or inflation in the early universe. Ref : Phys. Rev. D 86, 065016 (2012) , Phys. Rev. D 88, 085020 (2013)

ASI 2016 – Abstract Book 100

GRC-10 ASI2016_650 Sk Javed Rana Poster

Akshat Singhal, Varun Bhalerao, Sukanta Bose IUCAA, Pune-411007

Optimizing Method to Localize the Gravitational Wave Sources Using Electromagnetic Follow-up within a Setting Patch We are expecting to have the first direct discovery of gravitational waves (GWs) very soon. The detection of electromagnetic (EM) counter- parts will help immensely in characterizing its GW source, probing the nature of counterparts associated with compact binary coalescences, and enriching our understanding of their environments. The localized error regions (or patches) in the sky obtained from observations by GW detectors will be a few tens to a few hundreds of square-degrees wide, and may not be observable in a single night using an EM telescope. We have developed an algorithm to tile the patch, optimize the observing sequence, and maximize the probability of finding the EM counterpart. We have accounted for practical observing constraints, including the diurnal circle, target visibility and telescope availability. We performed extensive simulations to compare our algorithm with existing follow-up algorithms and found that the former does better in maximizing the probability of finding EM counterparts.

GRC-11 ASI2016_656 Shilpa Kastha Poster

K G Arun Associate Professor

Tracking the redshift evolution of merger rate density for double neutron star systems using gravitational wave detections We propose a method, which is a variant of the well-known V/Vmax test in astronomy, to track the redshift evolution of Double Neutron Star merger rate density, using Gravitational Wave (GW) observations by advanced GW detectors. We show that a distribution of 'redshifted' signal to noise ratio, defined by $\sigma=\rho (1+z)^{1/6} $ (where $\rho$ is the optimal signal to noise ratio of detected GW events), would follow a $p(\sigma)\propto {1\over \sigma^4}$ distribution if the DNS sources are distributed uniformly in the comoving volume for a non-evolving universe. We study how the expansion of the universe and the evolution of the comoving source rate density will affect this distribution and argue how this can be used to study the evolution of DNS merger rate density with advanced GW detectors. We then show how different these distributions would look for different models of DNS rate density evolution and discuss the abilities of future GW detectors to carry out the proposed test.

ASI 2016 – Abstract Book 101

GRC-12 ASI2016_673 Chandra Kant Mishra Poster

P. Ajith, Nathan Johnson-McDaniel (ICTS-TIFR, Bangalore, India) K. G. Arun (Chennai Mathematical Institute, Chennai, India)

Waveform modelling for binary black hole coalescences

We expect binary black hole (BBH) coalescences to be a prominent source for advanced ground-based gravitational-wave (GW) detectors, such as Advanced LIGO, with possibly tens or more events per year when the detectors are operating at design sensitivities. Both the detection and the subsequent analysis of these signals requires accurate modelling of the source. Even small deviations from the true signal can lead to a significant loss in detection rates and poor measurement of the source properties. The most accurate models for these signals are provided by numerical relativity (NR) simulations. However, these simulations are computationally expensive, and are thus only able to be carried out for a sparse sampling of the parameter space. Moreover, most NR simulations are not able to cover many orbits before merger. One thus uses as much information from approximation/perturbation techniques in general relativity as possible to make fast-to- evaluate models for the waveforms, which one calibrates to NR simulations. Currently, there are a number of such models, though they mostly focus on modelling the dominant quadrupolar mode of the waveform, though the real signal might have significant contributions from higher order modes. Neglecting the contributions from higher order modes might result in significant loss of detection rates or in biases in the recovery of the system's parameters. In this presentation I shall discuss the scheme we have developed to efficiently use available inputs from various approximation techniques/perturbation theory results in general relativity along with recent NR simulations to construct analytical waveform models including the effect of higher modes. These waveform models can be used to efficiently detect/analyse GW signals from BBH coalescences.

GRC-13 ASI2016_707 Sumit Kumar Poster

P. Ajith International Centre for Theoretical Sciences, TIFR, Bengaluru Thomas Dent, Badri Krishnan, Tito Dal Canton AEI Hannover

A new multi-detector coincidence test for the search for gravitational waves from compact binary coalescences

In a search for gravitational waves from compact binary coalescences using a network of detectors, the data are analyzed separately for each detector, to generate 'single-detector triggers'. A coincidence test is then performed on the reported triggers that checks the consistency of the signal parameters (such as the masses of the compact objects and the time of arrival of the signal) estimated from multiple detectors. We propose a coincidence test based on normal difference distribution of trigger parameters and calculating false dismissal probability for each set of triggers. We can choose to reject triggers for which false dismissal probability is below a certain threshold value. This formulation enables us to fold in the prior distribution of the sky location of compact binaries that is detectable by a detector network.

ASI 2016 – Abstract Book 102

GRC-14 ASI2016_722 Remya Nair Poster

Sanjay Jhingan, Centre for Theoretical Physics, JMI, Delhi Takahiro Tanaka, Department of Physics, Kyoto University, Japan

Synergy between ground and space based gravitational wave detectors

The gravitational wave (GW) community is looking forward to the launch of the much awaited space based interferometric detectors like eLISA and DECIGO. Once these waves are detected, the attention will turn to studying the GW sources and infer their characteristics, for example mass. The co-existence of the ground and space based telescopes may afford us considerable gain in the estimation of the source parameters. In this talk we'll discuss potential gain in estimating the parameters of a binary coalescence, by combining measurements of future ground and space based detectors. Using the post-Newtonian waveform for the inspiral of non- spinning neutron star-black hole binaries in circular orbits, we'll show how the estimates for the chirp mass and the symmetric mass ratio are improved by combining the data from different space-ground detector pairs. We'll also present results for the parameter characterizing deviations from GR within the parameterized post- Einsteinian framework.

GRC-15 ASI2016_751 Karthik A B Poster

Dr Firoza Sutaria, Indian Institute of Astrophysics Dr Subinoy Das, Indian Institute of Astrophysics Ms Swathi Karanth, Christ University Bangalore. Mr Karthik A B, Christ University Bangalore.

Unidentified 3.5kev line in Dwarf Galaxies,Dark Matter sources

Simulations of galaxy formation based on the Lambda Cold Dark matter (ΛCDM) cosmological model predict that a large galaxy such as the Milky Way should have many (~ 200) dwarf satellite galaxies. However, only about 20 or 30 have been identified. Where are the rest? Are they really there? Warm dark matter, constituting of sterile neutrinos, is lighter, and therefore resolves this issue as it erases structures in small scale. Recently, a previously unidentified, soft X-ray excess, at (3.55−3.57) ± 0.03 keV, in the spectra of some galaxies has been associated with the decay of sterile neutrino warm dark matter [Bulbul et al. 2014ApJ...789...13B]. Here, we report on our search for this weak, previously unidentified, emission line in the stacked XMM-Newton spectra of NGC 1399 of Fornax cluster, and the Draco dwarf spheroidal galaxy. We do not find evidence for this line in the NGC 1399. If it is the case that these weak signal are absent in dwarf spheroidal but present in stacked spectra of clusters reported by Bulbul et al., once explanation could arise from the difference in dark matter density profile in dspH and galaxy clusters. Especially, if the signal originates due to annihilation rather than decay, it would be very sensitive to DM density profile towards the centre of x-ray source.

ASI 2016 – Abstract Book 103

GRC-16 ASI2016_768 PRATEEK GUPTA Poster

Reju Sam John, PhD Student, PEC Pondhicherry University. Surajit Paul, Dept of Physics, S.P. Pune University. Revealing radio structures from filamentary inroads and cluster outskirts by numerical modelling of radio emissions The structures at Large-scale ( greater than few tens of Mpc ) in the Universe comprises of complex filamentary network of matter surrounding the large voids and connect the massive Galaxy clusters. Filaments are the main channels through which dark matter and baryons drains from voids and reach the nodes where the clusters are formed. Magnetic field in Galaxy clusters are presumably amplified by shock waves in Inter- Cluster Medium ( ICM ) which are generated during the formation of these structures. These shock compression also accelerate significant population of charge particles. Due to baroclinic instability at the junction of filaments and Galaxy clusters, a significant turbulence is generated which further amplify the magnetic field by dynamo action and also re-accelerate the charge particles which, in turn, produce synchrotron emission which could help in tracing back the dynamical history of these structures. In this work, we have developed models for computing radio emission from Large Scale Structures using Adaptive Mesh Refinement (AMR) based cosmological simulations. Computation is done on grid parameters and a proper weight has been used to nullify the effect of complicated resolution pattern of an AMR simulation. We have implemented both turbulent re-acceleration and Diffusive shock acceleration models to compute the radio emission. Finally, we have created synthetic radio maps and clearly predicted the possible detectability with the new generation Radio telescopes. This work of ours has resolved many issues with unexplained observed radio structures like radio relics found at few Mega parsec away from the Galaxy clusters as well as it has predicted some very interesting radio structure that will possibly be revealed by the new generation telescopes in near future.

GRC-17 ASI2016_792 Archana Sangwan Poster

H. K. Jassal Assistant Professor

Scalar field dark energy and current observations

The universe is undergoing accelerated expansion and a large number of models are proposed to explain it. These models include the cosmological constant model and models based on scalar fields. We analyse parameters of canonical scalar field models (quintessence) as well as noncanonical scalar field models, in particular the tachyon model and present observational constraints on their parameters. The different observations used are the type Ia supernovae data, the baryonic acoustic oscillations(BAO) data and direct measurements of hubble parameter H(z). The range of parameters of these models is strongly constrained by present observations. The allowed variation of the density of dark energy also allows us to constrain the shape of potentials, both canonical and noncanonical, which are consistent with current observations.

ASI 2016 – Abstract Book 104

GRC-18 ASI2016_796 Haris M K Poster

Dr. Archana Pai (IISER TVM)

A Hybrid detection statistic in coherent multi-detector binary gravitational wave Search

A global network of broad band advanced interferometric gravitational wave detectors like Advanced LIGOs and Advanced Virgo will be operational very soon. The Advanced LIGO detectors have a proposed distance reach of ∼ 445M pc. for binary neutron star (BNS) events and are expected to detect few events of BNS inspiral per month. In this work, we propose a new hybrid detection statistic to address the coherent multi- detector search of gravitational wave from compact binary coalescences with Neutron stars and Black Holes. The performance of the hybrid statistic is compared with that of the generic coherent multi-detector maximum- likelihood-ratio (MLR) statistic for different networks. Owing to the single synthetic data stream, the hybrid statistic gives low false alarms compared to the generic multi-detector MLR statistic and small fractional loss in the optimum SNR for a large range of binary inclinations. Thus, the hybrid statistic detect ∼ 7% more binary events compared to the generic multi-detector MLR statistic for a fixed false alarm probability of 10^−5 in the LIGO-Virgo network.

GRC-19 ASI2016_804 Ashutosh Tripathi Poster

H. K. Jassal Assistant Professor

Gamma Ray Bursts as cosmological probe

Recent work has shown that Supernovae of type Ic which are associated with Gamma Ray Bursts (GRBs) are potential candidates for standard candles. We constrain cosmological parameters using this data and combine it with the cosmology independent calibrated distance moduli of GRBs at high redshifts. The constraints obtained are significantly better than those obtained earlier, not only for models with constant equation of state but also those where dark energy equation of state is a function of time. We compare the results with those obtained from other observations. The cosmological constant model is consistent with these observations. The constraints obtained from GRBs are correlated with those obtained from type Ia supernovae data and are orthogonal to constraints obtained from baryon acoustic oscillation observations.

ASI 2016 – Abstract Book 105

GRC-20 ASI2016_824 Tabasum Poster

Tabasum Masood & Naseer Iqbal

Role of Peculiar Velocities of Galaxies in Gravitational Clustering of Cosmological Many Body Problem

This thesis presents a study of the role of peculiar velocity of galaxy clusters in cosmological many body problem. The cosmological many body problem can be defined in terms of the gravitational clustering of galaxies in an expanding universe. Many galaxies cluster together under the influence of mutual gravitation and tend to form the largest structures in the universe. The approach of gravitational quasi-equilibrium thermodynamic theory in combination with statistical mechanics have been used to describe these clustered structures. The theory describes galaxies as point masses each with same mass. However, the extension of this theory for extended nature of galaxies give also interesting results. Making use of correlation functions as a tool predicts important results which describe the overall status of dynamical parameters like virial mass, virial radius, virial temperature and peculiar velocity of galaxy clusters. The study of correlated relations among various dynamical parameters seems to be essential in describing the details of the problem. The study provides the dominance of clustering for gravitating particles in the interior regions of galaxy clusters. Using gravitational quasi equilibrium thermodynamics, we develop a theory related to the correlation functions that successfully explains the following: 1. The peculiar velocity of galaxy cluster results showing agreement with the results from observations and N-body simulations. 2. The output of cosmological simulations of galaxy clusters obtained by using Enzo hydro dynamical code for the equation of state shows a peculiar behaviour as expected in the inner regions of a cluster. 3. The results of various derived relations like T_{vir}, V_{pec} and R_{vir} have been used to compute the necessary constants involved in the expressions for the study. 4. The unique behaviour of entropy change of a cosmological system signifies the phenomena of gravitational phase transitions where the systems phase changes from mildly to highly clustered phase and from mildly to unclustered phase. According to this phase transition, two specific latent heats associated with phase transitions are evaluated for necessary physical significances.

GRC-21 ASI2016_884 Anuradha Poster

Anuradha Gupta, Sanjeev Dhurandhar, Sukanta Bose, Reetika Dudi

Towards an effective signal-based discriminator for searches of gravitational-wave signals from binary black hole coalescences Compact binary coalescences (CBCs) involving spinning black holes and/or neutron stars are the most exciting gravitational wave events for the second-generation laser interferometric detectors like Advanced LIGO and Advanced Virgo. A successful detection of CBC signals significantly depends on how well we discriminate them from the non-stationary and non-Gaussian noise artifacts present in the detector data. The chi-square time-frequency test is one of the most powerful ways to discriminate such noise transients from the genuine CBC signals. Unfortunately, this discriminator, as applied in the traditional way, does not perform very well for CBC signals with high mass and/or spins. We investigate in detail the factors that contribute to the failure of this discriminator in those regions of the parameter space. This helps us to develop a better and robust discriminator for high mass non-spinning and aligned-spin CBC searches. We describe our results for the same.

ASI 2016 – Abstract Book 106

GRC-22 ASI2016_898 Debottam Nandi Poster

Dr. S. Shankaranarayanan, IISER Thiruvananthapuram

Complete Hamiltonian analysis of cosmological perturbations at all orders.

Cosmological perturbation theory is currently a preferred mathematical procedure to compare the equations of gravity with precise observations. However, due to the difficulties in interpreting gauge-invariance and invertibility in Hamiltonian formalism, there is no consistent and generalized Hamiltonian analysis for cosmological perturbation theory at any order for any kind of model of gravity. In this work, using a simple model, we provide a simple mathematical approach to deal with all the difficulties to obtain a consistent Hamiltonian formalism and extend the approach to canonical scalar field. We show that our approach can be applied to any order of perturbation for any first order derivative fields. We also apply our approach to Galilean scalar field model and show that, there is no extra degrees of freedom, as expected, at every order of perturbation and obtain all consistent equations of motion. We compare and contrast our approach to the Lagrangian approach (Chen et al [2006]) for extracting higher order correlations and show that our approach is quick and robust and can be applied to any model of gravity and matter fields without invoking slow-roll approximation.

GRC-23 ASI2016_902 Kumar Atmjeet Poster

'Eric Chassande-Mottin, APC France; Archana Pai, IISER TVM; K Haris, IISER TVM

Probing mass-spin parameters of precessing NS-BH binaries

Compact binary systems (NS-BH and BBH) with at least one non-zero spin undergoes precession if the spin S is not aligned with the orbital angular momentum L. Precession results in the modulation of the emitted gravitational waveform which can be expressed in terms of a linear superposition of harmonics. Detection of individual harmonics from the advanced interferometric data would carry crucial astrophysical information about the precessing system. Using the fractional SNR contribution in various harmonics, we address an inverse problem of probing the astrophysical mass-spin parameters of the binary. The study is carried out for the SpinTaylorF2; a single spin precessing waveform for NS-BH systems.

ASI 2016 – Abstract Book 107

GRC-24 ASI2016_918 Praveer Tiwari Poster

Chandra Kant Mishra, Nathan Johnson-McDaniel, Ajith Parameswaran (International Centre for Theoretical Sciences-Tata Institute of Fundamental Research)

Modeling Mode Mixing in the Ringdown Phase of Binary Black Hole Coalescence

Coalescing binary black holes (BBHs) are among the most prominent sources of gravitational waves (GWs) and a precise understanding of their dynamics is crucial in order to extract useful information from detected GWs (using, e.g., the LIGO detectors). Here, we study the ringdown phase of a coalescing BBH, in which the final black hole created by the merger settles down from an excited state to a stationary state. Gravitational waves coming from this phase can be analytically modelled by solving Teukolsky's equation for linearly perturbed Kerr black holes. The solution of this equation has a natural decomposition in spin-weighted spheroidal harmonics. However, the gravitational wave strain is usually expressed as an expansion in spin- weighted spherical harmonics, and a given spheroidal harmonic contributes to more than one spherical harmonic, leading to the phenomenon of mode mixing. We describe our progress in including the effects of mode mixing in analytical models of the gravitational waveforms from binary black hole coalescences.

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ASI 2016 – Abstract Book 108

ASI-2016 Poster Presentations

Extragalactic Astronomy

EA-1 ASI2016_388 Shweta Srivastava Poster

N.G. Kantharia National Centre for Radio Astrophysics, TIFR,Pune

GMRT studies of Wolf Rayet Galaxies

We present radio continuum observations with the GMRT at 244 and 610 MHz of a small sample of Wolf Rayet (WR) galaxies. Galaxies containing the signatures of Wolf Rayet stars have been known as WR Galaxies. These observations are made to estimate the spectral indices which could help to clarify the nature of the radio emission. We also report the comparison of morphological features using radio, UV (GALEX) and IR (2MASS) and examine the influence of environment on the morphology of the radio continuum emission and spectrum.

EA-2 ASI2016_394 Sunil Chandra Poster

K. P. Singh Tata Institute of Fundamental Research, Mumbai Markus Böttcher NWU, Potchefstroom, South Africa

Synchrotron polarisation and SEDs during high energy flares in blazars

The blazars are characterised by the non-thermal broadband double-humped Spectral Energy Distribution (SED), with first one peaking at lower energies (submm to X-rays), whereas, the second peak lies in MeV-GeV band. The low energy emission in blazars are contributed by the synchrotron emission by the ultra-relativistic electrons and positrons in the jet. Whereas, the high energy emission is thought to be originated due to either the proton synchrotron, pion decay during hadronic interactions (Hadronic models) or attributed to the Inverse Comptonization (IC) of low energy seed photons in the jet (Leptonic models). A combination of both approaches are also utilised to explain the data, if needed. However, in most of the cases, leptonic models are good approximations for re-generating the observed SEDs in blazars. On the other hand, blazars show high variability, oftenly connected with the high and variable polarisation in the radio & optical bands, parameterised by the Degree of Polarisation (DP) and Position Angle (PA). The rotations or swings in PA are also seen in many high energy flares in blazars. The DP depends on the particle energy distribution, strength and topology of magnetic field. The DP may be significantly diluted with the un-polarized emission from other thermal components of SEDs, namely disk, torus, line-regions, host-galaxies etc. The PA, however, only depends on the topology of local magnetic fields. The polarisation observations, thus may uniquely be used to understand the nature of the magnetic field and the shock, a possible driver for flares in the blazars, if complemented with SEDs. Therefore, a time-dependent modelling of broad-band simultaneously observed SEDs and synchrotron polarisation can be used as a tool to understand these enigmatic systems. The unprecedented capability of ASTROSAT enables us to look for temporal evolution of flux at different parts of the SEDs. Thus, the timing and broad-band spectral studies of these objects may uncover many unseen properties of blazar jet. Few previous results and prospects of the coordinated ASTROSAT+Fermi+ground based platforms shall be discussed during the conference.

ASI 2016 – Abstract Book 109

EA-3 ASI2016_427 Ruta Kale Poster

National Centre for Radio Astrophysics, TIFR, Pune

Spectra of brightest cluster galaxies

Brightest cluster galaxies (BCGs) are the most massive galaxies in the Universe that form at the centres of galaxy clusters. The AGN and radio activity from the supermassive blackholes at the centres of these galaxies are believed to play a major role in heating the intra-cluster medium. We investigate the optical spectra from the Sloan Digital Sky Survey of a large sample of BCGs in massive clusters. We classify the BCGs into star forming and AGN type based on their locations in the diagnostic diagrams. The connection between the spectral properties of the BCGs and the occurrence of radio sources in them will be presented.

EA-4 ASI2016_441 Rahna P T Poster

Rahna P.T. (Christ University, Bengaluru) Gudennavar S. B. (Christ University, Bengaluru) Bubbly S. G. (Christ University, Bengaluru) Rajesh Gopal(CMR Institute of Technology, Bengaluru) Jayant Murthy (Indian Institute of Astrophysics, Bengaluru)

Dust lane spheroidal galaxies in GALEX, SDSS, 2MASS, WISE and IRAS bands

The advancement of new observing facilities and large multi-wavelength surveys in astronomy has allowed us to study more galaxies than ever before. Dust lane spheroidal galaxies (DLSGs) show peculiar lanes of dense obscuring interstellar dust against their background, which are remnants of recent mergers. The main goal of this work is to use data spanning UV to IR from Galaxy Evolution Explorer (GALEX GR7), Sloan Digital Sky Survey (SDSS DR12), Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS) and Infrared Astronomical Satellite (IRAS) surveys to explore the different physical parameters of DLSGs in the nearby universe. Our sample consists of 280 DLSGs for which we have calculated their stellar mass, star formation rate (SFR), dust mass and other related parameters. We use relations from literature to calculate the parameters and compare with the results from SDSS template fitting method. We will be further looking into more galactic parameters and the correlations between them.

ASI 2016 – Abstract Book 110

EA-5 ASI2016_450 Atul Mohan Poster

Yogesh Wadadekar, NCRA-TIFR

Radio properties of optically selected quasars

Radio properties of quasars and the physical mechanism responsible for the radio emission are not fully understood even after 50 years of their discovery. Only ~10% of optically selected quasars have fluxes high enough to be detectable in large area radio surveys. However, by stacking radio images at the positions of optically selected quasars, we can study the average radio properties of these objects at flux levels well below the flux limit of the radio survey. We use optical quasar catalogs from the Sloan Digital Sky Survey (SDSS- DR7) and radio images from the VLA FIRST survey to study the radio and optical properties of a sample of > 10^5 quasars. We investigate the interdependence of quasar properties such as radio luminosity, radio loudness and optical color and their evolution with redshift. This is done by stacking various carefully selected sub- samples from our large optically selected quasar catalog.

EA-6 ASI2016_470 Sheelu Abraham Poster

Sudhanshu Barway, South African Astronomical Observatory, Cape Town South Africa Yogesh Wadadekar, National Centre for Radio Astrophysics, Ganeshkhind, Pune, India Ajit K Kembhavi, IUCAA, Ganeshkhind, Pune, India

Does the formation scenario of S0 galaxies depend on their stellar mass?

We present a study of the stellar mass dependence of the evolution of ~320 S0 galaxies in SDSS r band using bulge-disc-bar correlations. We extracted galaxy structural parameters for the bulge, disc and bar using GALFIT, a 2-D image decomposition code. We have multi-wavelength data on these S0 galaxies using which we measure total stellar mass, colours etc. We have created a catalogue of these parameters as well as those available from SDSS database along with structural parameters in r-band. We confirm earlier results from our research group and find that various scaling relations involving bulge and disc parameters show dependence on stellar mass. We can broadly divide S0 galaxies into two classes in which massive S0 galaxies form via fast processes like quenching of star formation through major mergers while less massive galaxies formed through a different mechanism involving slow secular evolution processes where star formation is still ongoing. The fraction of barred galaxies, which comprises 17% of our S0 galaxies, also shows mass dependence. i.e. less massive S0 galaxies are more likely to host bars than massive S0 galaxies. Stellar populations in these S0 galaxies reveal that massive galaxies are dominated by old stellar populations while less massive S0s showing recent star formation activity and may contain young stars with age ~10^8 yr. These results provide evidence that the formation history of S0 galaxies follows two very different routes and which depends primarily upon the mass of the galaxy, though the environment also plays a significant role.

ASI 2016 – Abstract Book 111

EA-7 ASI2016_499 Mahadev Baburao Pandge Poster

J.P.Dange Mahatma Bashweshwar College, Latur. (MS) India 413512

Optical Imaging & Spectral Study of FR-I Type Radio Galaxy:CTD86

We present optical imaging and spectroscopic study of the Fanaroff & Riley class I radio galaxy CTD 86 based Hubble Space Telescope (HST) and Sloan Digital Sky Survey (SDSS) observations. Based on isophotal analysis, we have shown that there is no stellar disk component within CTD 86 and the morphological class of the galaxy is E2. CTD 86 has a weak optical emission line spectrumtypical of type 2 AGN. Optical spectroscopy of CTD 86 has revealed the presence of only narrow emission lines, thus making it a narrow-line radio galaxy. We have also measured the central stellar velocity dispersion for CTD 86 using the available SDSS spectrum. Galaxy stellar kinematics were extracted from the absorption-line spectra of CTD 86 using Penalized Pixel-Fitting method and which is equal to be, and calculated the black hole mass, MBH = (8.8 ± 2.4)x 107 M⊙ .

EA-8 ASI2016_515 Suchetana Chatterjee Poster

Newman, Jeffrey A. (University of Pittsburgh), Jeltema, Tesla (UC Santa Cruz), Myers, Adam D. (University of Wyoming), Aird James (University of Durham) Coil, Alison L. (UC San Diego), Cooper, Michael (UC Irwine) Finoguenov, Alexis (University of Helsinki), Laird Elise (Imperial College), Montero-Dorta, Antonio (University of Utah) Nandra, Kirpal (MPE) Willmer, Christopher (University of Arizona) Yan, Renbin (University of Kentucky)

Feedback from Active Galactic Nuclei: Implications from X-ray Surface Brightness Profiles of Galaxies

With data from the All Wavelength Extended Groth Strip International Survey (AEGIS), we tentatively detect the extended X-ray emission in the interstellar medium (ISM)/intra-cluster medium (ICM) in both active and normal galaxies at 0.3 <= z <= 1.3. The analysis was carried out using matched samples of active galactic nuclei (AGN) host and normal galaxies. We detect excess X-ray emission at scales of 1--10 arcsec at a few sigma significance in the surface brightness profiles of normal galaxies. The observed excess in the surface brightness profiles is suggestive of lower extended emission in AGN hosts compared to normal galaxies. This is qualitatively similar to theoretical predictions of the X-ray surface brightness profile from AGN feedback models, where feedback from AGN is likely to evacuate the gas from the center of the galaxy/cluster. We discuss the uncertainties related to the interpretation of this result and propose prospects of improvement.

ASI 2016 – Abstract Book 112

EA-9 ASI2016_519 Veeresh Singh Poster

Alexandre Beelen (IAS, Orsay, France), Yogesh Wadadekar (NCRA-TIFR, Pune), C.H. Ishwara-Chandra (NCRA-TIFR, Pune), Sandeep Sirothia (NCRA-TIFR, Pune; SKA CapeTown)

Unveiling Active Galactic Nuclei (AGN) population in distant dusty galaxies

Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of high-redshift Active Galactic Nuclei (AGN). We unveil the population of radio-loud AGN at higher redshifts using one of the deepest existing radio continuum surveys (GMRT, VLA) combined with deep optical (Subaru, VLT-VIMOS), IR (Spitzer) and Far-IR (Herschel) observations in the XMM-LSS extragalactic field. We find that the majority of these radio-loud AGN distributed over redshifts ~ 1 to 4, are only moderately powerful, compact and hosted in star-forming dusty galaxies. It is believed that these sources represent initial stage of the evolutionary sequence of radio galaxies, at which radio jets are still confined by the dense cool gas. These radio AGN are likely to be the progenitors of powerful radio galaxies in the local Universe.

EA-10 ASI2016_521 Mridweeka Singh Poster

Mridweeka Singh, Kuntal Misra, Anjasha Gangopadhyaya, Subhash Bose, D.K.Sahu, Raya Dastidar, Brijesh Kumar, G.C. Anupama, S.B. Pandey Affiliation- Aryabhatta Research Institute of observational sciencES (ARIES) Nainital, 263002

The behavior of supernova SN 2014cy in the optical wavelength

The supernovae (SNe) of type II prominently exhibit presence of hydrogen in their early spectra and are a result of the core collapse of massive stars. These SNe show a wide variety of light curve and spectral properties. A detailed analysis of individual SNe allows us to study the peculiarities seen in the different sub- classes of type II SNe. In this poster we present the optical observations of a type IIP SN 2014cy which occurred in the galaxy NGC 7742. High cadence photometric observations, covering a span of ~150 days, were taken with the 1.0m class telescopes at ARIES. Supplementary spectroscopic observations were taken with the 2.0m Himalayan Chandra Telescope at IAO, Hanle. The light curve evolution in different phases allows us to estimate various physical parameters such as the Ni mass, ejected mass and progenitor mass. We also present a comparison of the physical properties of a sample of other well studied type IIP SNe.

ASI 2016 – Abstract Book 113

EA-11 ASI2016_532 Arun Mangalam Poster

A model for jet polarization and emission in blazars

Blazars exhibit strong flares seen in $\gamma$-rays, X-rays, and optical/NIR bands. We implement a realistic magnetic surface geometry in a general relativistic model to describe effects on emission from orbital features in the jet close to the black hole horizon radius. The overall boost factor $g$ depends on the black hole mass, the bulk Lorentz factor of the blob and the angle between the direction of the photon to the observer and the instantaneous velocity of the blob.The calculation predicts a strong correlation or anti-correlation between optical flux and degree of polarization during the flare and corresponding rapid swings in polarization angle for optically thin synchrotron emission with helical magnetic fields. We compare these properties with recent observations of 3C 454.3.

EA-12 ASI2016_535 Dhruba Dutta Chowdhury Poster

Dr. Suchetana Chatterjee Assistant Professor Department of Physics Presidency University 86/1, College Street, Kolkata-700073 Estimating the Sunyaev-Zeldovich signal from quasar hosts using a Halo Occupation Distribution based approach The Sunyaev-Zeldovich (SZ) effect is a spectral distortion in the Cosmic Microwave Background (CMB), caused due to inverse Compton scattering of CMB photons by high energy electron distributions. While the largest SZ distortion in the CMB is caused by the hot electrons present in the intra-cluster medium (ICM), several other small scale astrophysical processes can also contribute to it. Analytic studies have shown that the interstellar electron gas of a quasar host galaxy heated by feedback can cause substantial SZ effect. However, for successful detection of the quasar feedback signal, SZ signal from the ICM of the host dark matter halo in which the quasar resides needs to be properly quantified. In my thesis, I have calculated the possible average SZ signal from the ICM in quasar host halos. For this purpose, I made an analytic model for the ICM gas following the prescription of Komatsu and Seljak (2001). In addition to the above, I used the quasar halo occupation distribution (HOD) model of Chatterjee et al. (2012) with measured HOD parameters from Richardson et al. (2012). My results show that within the statistical errors of the HOD (Richardson et al. 2012), it is not possible to disentangle the quasar feedback signal from the halo gas signal. Recently, Ruan et al. (2015) experimentally obtained an average SZ signal by stacking Planck SZ maps correlated with the location of SDSS quasars. While they claimed to have found signatures of quasar feedback, I find that their signal could be originating from the quasar hosts located at the high mass tail of the HOD whose number has large statistical uncertainties (Richardson et al. 2012).

ASI 2016 – Abstract Book 114

EA-13 ASI2016_539 Sayan Biswas Poster

Pooja Bhattacharjee (Bose Institute, Kolkata, India), Pratik Majumdar (Saha Institute of Nuclear Physics, Kolkata, India), Mousumi Das (Indian Institute of Astrophysics, Bengaluru, India), Partha S. Joarder (Bose Institute, Kolkata, India), Pijushpani Bhattacharjee (Saha Institute of Nuclear Physics, Kolkata, India) Searching for signatures of dark matter annihilation from low surface brightness galaxies using FERMI gamma ray data The physical nature of dark matter remains enigmatic even in these days of the advent of modern physics and astrophysics. Recent experimental evidences as well as theoretical arguments favor the existence of some form of non-baryonic cold dark matter (CDM) for explaining large scale structure of the Universe. Although such dark matter is supposed to constitute about one fourth of the total energy density of the Universe, its exact nature is not yet understood. Weakly interacting massive particles (WIMPs), predicted in several theories beyond the Standard Model (of particle physics), are the most probable candidates for CDM. Pair annihilation (or decay) of WIMPs would yield particles such as neutrinos, (anti-) protons and electron-positron pairs simultaneously producing a significant flux of high energy gamma rays. Low surface brightness (LSB) galaxies are one of the most dark matter dominated galaxies that we know of. Hence these galaxies are ideal laboratories for indirect dark matter search through the observations of dark matter (or decay) products. In t his paper, we have chosen a set of LSB galaxies and analyzed the FERMI data, obtained from these galaxies over approximately seven years, in the energy range 100 MeV to 50 GeV. We have determined the upper limits of gamma ray fluxes from those sources by fitting the data with spectra of appropriate power-law behavior. The theoretically possible gamma ray fluxes originating from WIMP annihilation in each of such sources can be divided into two factors, namely, the ``astrophysical factor'' and the ``particle physics factor''. Here, the astrophysical factors pertaining to each LSB galaxy are calculated by taking a standard dark matter density profile and the corresponding halo properties into account. These astrophysical factors are further used to calculate the particle physics factors so that a plausible (theoretical) upper limit of gamma ray flux due to the annihilation of WIMPs in each of the LSB galaxies, examined in this paper, is finally obtained. Such comparisons between theoretical and observational upper limits of gamma ray fluxes from LSB galaxies would hopefully be useful to put constraints on the pair-annihilation cross section of WIMPs in various widely studied extensions of the standard model including its supersymmetric extensions. The gamma ray limits presented by us may also constrain some WIMP models proposed to explain FERMI and PAMELA electron- positron data.

ASI 2016 – Abstract Book 115

EA-14 ASI2016_542 T Mageshwaran Poster

A. Mangalam (Indian Institute of Astrophysics, Bangalore)

Jet and accretion dynamics of tidal disruption events

A supermassive black hole influences the orbital and spatial distribution of stars in the inner parsec region of its host galaxy which together determine the ingestion rate of stars; this results in tidal disruption events (TDEs) where the stars are disrupted by the strong tidal gravity of the hole. By using orbital elements of the star, namely the energy and angular momentum, we make predictions for the physical parameters of the disk that is formed after a TDE. We then self-consistently calculate the time evolution of the relativistic accretion disk and determine the mass and angular momentum feeding rate into the hole; this allows an estimate of the jet power modeled by the Blandford-Znajek process. Using standard cosmological parameters and instrument details, we predict the detectable rates for the various radio surveys and compare our results with observations of radio transients.

EA-15 ASI2016_546 Alka Mishra Poster

N. G. Kantharia, National Centre for Radio Astrophysics (NCRA-TIFR), Pune Mousumi Das, Indian Institute of Astrophysics, Bangalore

HI gas content in Giant Low Surface Brightness (LSB) Galaxies

In this paper we study the 21cm HI line emission from four low surface brightness (LSB) galaxies. The observations made using the Giant Metrewave Radio Telescope. LSB galaxies are generally large, dark matter dominated spirals that have low star formation efficiencies and large HI gas disks. Their properties suggest that they are less evolved compared to high surface brightness galaxies. We present GMRT HI emission maps of LSB galaxies with an optically-identified active nucleus. Using our HI data and data from literature , near- infrared (2MASS) and near-ultraviolet (GALEX), we studied morphology, kinematics and star formation efficiencies in these galaxies. The HI emission of three galaxies; UGC 1922, UGC 4422 and UM 163 show HI disks of similar extent to stellar disk whereas UGC 1378 shows extended HI disk. All the sample galaxies show asymmetric HI distribution and rotating disk. The HI masses in the observed galaxies are ≥ 10^10 M⊙ .

ASI 2016 – Abstract Book 116

EA-16 ASI2016_547 LABANI MALLICK Poster

Gulab C. Dewangan, IUCAA, Pune

RMS Spectral Modelling – a powerful tool to probe the origin of variability in AGN

The broadband energy spectra of Active Galactic Nuclei (AGN) are very complex in nature with contribution from many ingredients: accretion disk, corona, jets, broad-line region (BLR), narrow-line region (NLR) and Compton-thick absorbing cloud or TORUS. Therefore energy spectral modelling can encounter degeneracy problem, e.g, it is not well understood whether the broad Fe K line feature near 5-7 keV is due to blurred reflection or complex absorption and hence mean spectral study is not sufficient to distinguish between the nature of variability produced by different components. The origin of variability could be pivoting of the primary continuum, reflection and/or absorption. The study of RMS (Root Mean Square) spectra would help us to connect the energy spectra with variability. In this work, we study the energy dependent variability of AGN by developing theoretical RMS spectral model in ISIS (Interactive Spectral Interpretation System) for different input energy spectra. In this talk, I would like to present results of RMS spectral modelling for few radio-loud and radio-quiet AGN observed by XMM-Newton, Suzaku, NuSTAR and ASTROSAT and will probe the dichotomy between these two classes of AGN.

EA-17 ASI2016_551 Sandeep Kumar Kataria Poster

Sandeep Kumar Kataria(JAP-IIA,Bangalore) Mousumi Das(IIA,Bangalore) Lukas Konstandin(University of Exeter) Studying the Formation and Structure of Bars in Dark Matter Dominated Spiral Galaxies using Gadget-2 Simulations We present N body simulations of bar formation in dark matter dominated galaxies which is very less understood with theory. Bars are elongated features found in the centers of spiral galaxies as a result of disk instabilities. Nearly two thirds of all observed spiral galaxies in the nearby universe have bars. The main goals of our study is to investigate the effect of various halo parameters such as halo concentration, triaxiality, mass and profile on the formation of bars in disk galaxies. We will compare our results of bar morphologies and bar lengths in dark matter dominated galaxies to those in found in normal galaxies. The first part of the simulation involves the generation of isolated galaxies using GalIC code (D. Yurin and V. Springel), which contains stellar disc and dark matter particles. The second part consists of evolving these galaxy models with N- body/SPH code(Gadget-2, V. Springel) up to time scale of 10 Gyr. We studied effect of the following halo parameters. (i) Halo Concentration : We first generated the disk galaxies with different halo concentration varying from c= 5 to 20 where c= R_{vir}/ R. We evolved these models up to 10 Gyr. We found that as the halo concentration increases, the bar formation is suppressed. (ii) Halo Triaxiality: In this case also we made different galaxy models with having prolate and oblate shape having axis ratios from 0.8 to 1.2. We are evolving these galaxy models and continuing with analysis. In future we will include a gas component in our simulations in order to study how the gas affects the overall bar morphology and the formation of other disk instabilities. In this presentation we discuss some early results of our study.

ASI 2016 – Abstract Book 117

EA-18 ASI2016_552 Dipanweeta Bhattacharyya Poster

A. Mangalam (Indian Institute of Astrophysics, Bangalore)

$M-\sigma$ relationship and Galactic structure

There is a well known observed correlation between the mass, $M_\bullet$, of Supermassive black hole (SMBH) at the center of massive galaxies and velocity dispersion $\sigma$ of the stars in the galaxy with $M_{\bullet} \propto \sigma^p$ where $p=4-5$ is empirically indicated. We build stellar distribution functions (DF) for stellar systems around the black hole taking a form $f(E, J)$ of the Evans type that is constrained by typical intensity profiles of elliptical galaxies. We self-consistently calculate the $\sigma$ profile from the inverted stellar mass density derivable from the Nuker form, thereby deducing the total potential including the black hole. We thus derive the $M_\bullet-\sigma$ relation taking a constant ratio of bulge to black hole mass with dispersion calculated from various methods: sphere of influence, circular orbit velocities and also using the velocity dispersion profile directly constructed from the DF; we find constraints on the DF form so that the derived $p$ is in the range $4-5$ across the methods. The model can be applied to and parameters derived for few realistic systems for which the surface density profile, dynamical mass and observed velocity dispersion are available.

EA-19 ASI2016_559 Ashok K. Singal Poster

1. Ashok K. Singal, Physical Research Laboratory, Ahmedabad 2. Shweta Srivastava, Physical Research Laboratory, Ahmedabad

The largest known head-tail radio galaxy IC 711

We present 20 and 50 cm maps of IC 711, perhaps the largest known head-tail radio galaxy, extending to 18' (almost a Mpc). The galaxy lies in Abell cluster 1314 which hosts another radio galaxy IC 708 in the peculiar shape of a highly bent bow (Rama's Dhanush!). We endeavour to unravel some of the mysteries of these radio galaxies and their host cluster Abell 1314

EA-20 ASI2016_597 Firoza Sutaria Poster

F. Sutaria (IIA, Bangalore) M. Safonova (IIA, Bangalore), R. Roy (The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden.)

Exploring star formation in Supernovae host galaxies:

We present here the results from our program to map the metallicity of star forming regions, in the host galaxies of core collapse supernovae (CC-SNe). This work focuses on events in progenitors with extended H- envelopes, and 8 - 15 M$_{\odot}$ ZAMS masses. CC-SNe rates being tracers of the massive star formation history of the host galaxy, it is natural to connect the properties of the progenitors with that of the host galaxies. By tracing the metallicity of the host, and particularly, its value at the SN position we also set stringent observational constraints on the transient's environment, as well as on the nature and mechanism of the progenitor-environment interaction.

ASI 2016 – Abstract Book 118

EA-21 ASI2016_601 Pratik Dabhade Poster

Madhuri Gaikwad (NCRA)& Joydeep Bagchi (IUCAA)

Discovery and multiwavelength analysis of Giant Radio Galaxies

Giant radio galaxies (GRGs) are a class of radio galaxies with linear sizes greater than 0.7 Mpc thus making them the largest single object known to us in the Universe. They are rare among the entire population of radio galaxies (RGs). Their physical evolution is not well understood so far. Most of the sources show bright hot spots at the edges and hence are classified as FR-II type radio sources. These radio sources host an active galactic nuclei (AGN) at the centre. It is believed that the “central engine”in the AGN is responsible for the production of bipolar relativistic jets. Largest known GRG is about 5 Mpc in projected linear size. In the past 60 years thousands of radio galaxies have been found, but less than 150 GRGs are only known so far which makes them very rare. GRGs owing to their large sizes and relatively low surface brightness, makes it difficult for their detection via automated search algorithms in various radio surveys. We have carried out non automated systematic search for GRGs. As a result we have found about 30 giant radio galaxies (GRGs) from the NRAO VLA SKY SURVEY (NVSS). Our discovery sample of GRGs have contributed to this field significantly. Questions about their rarity and exceptional large sizes have not been answered so far. In an attempt to answer one these questions we have started to study the host galaxy properties of these GRG in greater details. We have for the first time attempted to study the black hole properties of hosts of the GRGs. Studies in past three decades has provided strong evidences about black holes being the central engine responsible for powering these long and highly collimated radio jets in these GRGs. Interesting results of this study will be presented. The host galaxies of the GRGs were also studied for the first in mid-IR using the WISE telescope data. This has enabled us to classify for the very first time the GRGs into high & low excitation (LERGS & HERGS). WISE has unique capabilities of picking up high redshift AGNs as well as dust obscured AGNs. We also have developed a new technique of identifying radio loud quasars using WISE data along with radio data. This has enabled us to identify some of our GRGs as Giant radio quasars (GRQs) which are even more rarer than GRGs. These GRQs challenge the existing AGN unification scheme. These all results will be presented in greater details.

EA-22 ASI2016_604 Arunava Mukherjee Poster

A. Dhani (IIT-Roorkee) A. Ghosh (ICTS-TIFR) P. Ajith (ICTS-TIFR)

Constraining population synthesis models of compact binary coalescence using gravitational wave observations Coalescing binary systems comprising compact objects (neutron stars or black holes) are believed to be the primary sources of gravitational waves (GWs) for ground-based GW detectors like LIGO. These compact objects are the end products of stellar evolution. One can use the method of population synthesis to create astrophysical models predicting the evolution of these binary stars; here we consider the case of binaries in galactic fields. Since several physical and astrophysical processes governing binary evolution are not very well understood, different models differ greatly in their predictions of coalescence rates as well as the mass and spin distributions of compact objects. GW observations of compact binaries can constrain population models, shedding light on the uncertain physics and astrophysics of compact binary evolution. In this talk I will discuss the use of Bayesian statistical inference to extract the properties of coalescing compact binary populations, and to constrain population synthesis models. ASI 2016 – Abstract Book 119

EA-23 ASI2016_606 Viral Parekh Poster

K.S. Dwarakanath (RRI) Ruta Kale (NCRA) Huib Intema (Leiden University)

Detection of diffuse radio sources in MACS clusters

Origin of cluster scale diffuse radio emission is an open quest even with sensitive radio observations. There are approx. 40-50 clusters are hosting diffuse radio sources to the date. The goal of the work is to extend our current knowledge of the radio halo and relic populations to z >~ 0.3. In this talk, we will present archival radio (GMRT+EVLA) and X-ray (Chandra) data analysis of six MACS (MAssive Cluster Survey) clusters. These six clusters are massive and dynamically disturbed. We found that out of six clusters, two clusters host confirmed radio halos, two clusters host candidate radio halos, and remaining two are upper limit clusters. We also estimate the X-ray cluster morphological parameters (Gini, M20 and Concentration) for these MACS clusters. We confirm that diffuse intra-cluster radio sources are associated with major mergers.

EA-24 ASI2016_608 Priyanka Rani Poster

C.S.Stalin, Associate Professor

Correlation between X-ray and optical flux variations in AGN

One of the long standing problems in active galactic nuclei (AGN) is a clear understanding on the relation between optical and X-ray flux variations in Seyfert 1 galaxies, a category of AGN. This lack of knowledge is mainly due to the non-availability of quality and simultaneous optical and X-ray observations. Two main theories exist in literature on the connection between optical and X-ray flux variations in AGN, namely (a) optical photons are the reprocessed X-ray photons and (b) X-ray photons are the Compton upscattered optical photons. If either of the above two models are correct, then their effects could be observable in the flux variations displayed by AGN. Therefore, an effective approach to constrain the validity of the above two models is to carry out a systematic study on the correlations between optical and X-ray flux variations. We have carried out a systematic study on the optical and X-ray flux variations on a sample of about a dozen AGN. The observational data used in this work are from Swift and XMM-Netwon. Details of this work will be presented.

ASI 2016 – Abstract Book 120

EA-25 ASI2016_613 Avinash Singh Poster

Authors: Avinash Singh(1,2), Shubham Srivastav(2), G.C. Anupama(2), D.K. Sahu(2) Affiliation: 1. Joint Astronomy Programme, IISc; 2. Indian Institute of Astrophysics

Optical Analysis of the Type II Supernova ASASSN14dq

Supernova ASASSN14dq was discovered at a V-band magnitude of ~15.7 on July 08, 2014 in the dwarf galaxy UGC 11860(z~ 0.010424) at approximately 9" from the galactic center and was classified initially as a Type II supernova. The supernova was monitored in the optical wavelengths using the HFOSC instrument installed at the 2.0m Himalayan Chandra Telescope(HCT). The observations were done at 38 epochs spanning a period of over 6 months ranging from July 15, 2014 to Jan 25, 2015. The UBVRI broad-band photometric and low-resolution spectroscopic data were used to study the light curve and spectroscopic evolution of the supernova. The explosion parameters such as the photospheric temperature, the peak absolute magnitude, Ni- 56 mass, kinetic energy of the ejecta were estimated based on the parametric fits to the light curve and the modelling of the spectra using SYNOW. Also presented is a discussion on the progenitor mass and the supernova environment.

EA-26 ASI2016_632 Raya Dastidar Poster

Raya Dastidar, Brijesh Kumar, Subhash Bose, Anjasha Gangopadhyay, Mridweeka Singh, Kuntal Misra, S.B.Pandey Affiliation- Aryabhatta Research Institute of observational SciencES (ARIES) Nainital, 263002

Study of type IIb Supernova 2012P and its host galaxy

Type IIb supernovae form a distinct class, which shows a transition from type II to type Ib during their evolutionary phases. Their spectra shows strong hydrogen features in the early phases, followed by appearance of helium lines in late phases. The progenitors leading to such kind of explosion are not fully understood. The study of star forming regions within host galaxies can predict the possible progenitor channel of these explosions. If supernova explosion happens to be close to a star forming region, then the observation of HII knot will provide fair estimation of site metallicity. In this poster, we present progenitor properties using newly obtained narrow band H-alpha images of NGC 5806 (D ~ 25 Mpc), host to SN2012P, a type IIb event, observed from 1.3m Devasthal Fast Optical Telescope at ARIES, Nainital. The HST pre-explosion images of NGC 5806 is also available in the archive. We will also present analysis of 22 epochs of photometric observation, obtained from the 1m class telescopes at ARIES, along with 3 epochs of spectroscopic observation from other facilities.

ASI 2016 – Abstract Book 121

EA-27 ASI2016_633 Anjasha Gangopadhyay Poster

Anjasha Gangopadhyay, ARIES Kuntal Misra, ARIES Ramkesh Yadav, NARIT Dipankar Bhattacharya, IUCAA, Ranjeev Mishra, IUCAA, Gulab Chand Dewangan, IUCAA

The X-Ray rich supernova SN 1978K

Core collapse supernovae, due to interaction of the shock wave with the circumstellar medium, show emission in the X-ray wavelengths. SN 1978K is one of the X-ray rich supernova with long lasting X-ray emission in the recent times. SN 1978K was observed with XMM-Newton telescope in 2006 for 120ks. We present the X-ray spectral analysis of SN 1978K. The spectrum is best fit with a "dual vnei" model having variable elemental abundances. Our analysis shows the presence of two temperature plasma - one with a higher temperature and other with a lower temperature. We combine the X-ray analysis with the optical to study the evolution of velocity structure of the circumstellar medium.

EA-28 ASI2016_671 Omkar Suresh Bait Poster

Sudhanshu Barway(SAAO) Yogesh Wadadekar(NCRA-TIFR)

SED fitting for S0 galaxies using GALEX-SDSS-2MASS-WISE photometry

We present results from fits to the spectral energy distribution (SED) of a sample of S0 galaxies using panchromatic data from far UV to mid-IR from GALEX-SDSS-2MASS-WISE photometry. We use the publicly available code MAGPHYS to fit the SED and to estimate various physical parameters like stellar mass, star formation rate, mass weighted stellar age, metalicity etc. We find that S0 galaxies can be classified in two types based on their stellar mass. The star formation history of these two types of S0 are very different. High mass S0‟s have formed by major mergers at roughly the same epoch around z ∼ 2 after which star formation is rapidly quenched. On the other hand, low mass S0‟s are still seeing some star formation although the rate is decreasing, through various processes like ram pressure stripping for galaxies in clusters and bar driven instabilities in field galaxies.

ASI 2016 – Abstract Book 122

EA-29 ASI2016_685 Ashwani Pandey Poster

Ashwani Pandey Affiliation : Aryabhatta Research Institute of Observational Sciences Manora Peak, Nainital, 263002, India

Optical Quasi-Periodic Oscillations in the blazar PKS 2155-304

The optical (R-band) light curve (~12 yrs) of the blazar PKS 2155-304 has been constructed by combining the publicly available SMARTS data and the ROTSE data. The light curve is, then, searched for any possible periodicities by using the structure function (SF) and discrete correlation function (DCF) techniques. We find eight possible periods which indicate two possibilities : a quasi-periodic oscillation (QPO) with an average period of ~311 days (~0.85 yr) and multiple periods of ~ 230 days (~0.63 yr) and ~550 days (~1.5 yr) with their harmonics and three independent periods of ~1270 days, ~1970 days and ~ 2490 days. No direct model explaining these year-like periodicities is available till date, however year-like periodicities are often found in many blazars. We discuss various possible physical processes responsible for year-like QPOs as well as models explaining multiple periods.

EA-30 ASI2016_693 Mubashir Hamid Mir Poster

Ranjeev Misra (IUCAA, PUne), Mayukh Pahari (IUCAA, Pune) , Naseer Iqbal (K.U, Srinagar), Naveel A. Wani (K.U, Srinagar)

Model for the enigmatic energy-dependent time lags and rms of the heartbeat oscillations in GRS 1915-105

We report the discovery and modeling of enigmatic energy-dependent time lags of the order of few sec in the heartbeat state of GRS 1915-105. The lags for the fundamental show turn around ~10 keV while for harmonic they keep rising to at leat 10 keV. We have proposed the model based on the delayed response of the inner disk (DRIOD) radius to the accretion rate. The fluctuating accretion rate drives the oscillations of the inner disk after a time delay while the power-law respond immediately. We show that in this combined (diskbb+powerlaw) model based on the (DRIOD), a pure sinusoidal oscillation of the accretion rate explains not only the energy dependent rms and time-lag spectra of fundamental but also that for next harmonic with just four free parameters. Thus the lags of few secs which cannot be attributed to time travel effects or Comptonization delays can be explained by delays in the spectral components.

ASI 2016 – Abstract Book 123

EA-31 ASI2016_713 Niladri Paul Poster

Niladri Paul IUCAA

Modelling the Luminosity-dependence of Galaxy Clustering using Extreme Value Statistics and the Halo Model Data suggests that central galaxies have narrow width in their luminosity distribution function compared to that of the satellite galaxies. This leads to the debate on whether the luminosity of the centrals is drawn from some special luminosity distribution function. The speaker will show that the assumption of the luminosity of the centrals being the statistical extreme of a universal luminosity function is consistent with the narrow width in their luminosity distribution. In addition to that, this model can consistently predict the luminosity dependence of the two-point clustering of the galaxies. The speaker will show that one needs to incorporate halo-mass dependence in the universal luminosity distribution function to satisfy these requirements. This model reduces the complexity of the standard Halo Occupation Distribution(HOD) and the Conditional Luminosity Distribution Function(CLF) based approaches. The halo-mass dependence of the magnitude-gap between the brightest and the second brightest galaxy in a group will be discussed.

EA-32 ASI2016_736 Dilpreet Kaur Poster

Dilpreet Kaur(CSSTEAP-UN/PRL), S Ganesh(PRL), KS Balian(PRL),Ratna(PRL), Sunil(PRL/TIFR), UC Joshi(PRL).

Blazar OJ 287 : A Photometric variability study

The unified model of Active Galactic Nuclei(AGN) postulates that radio galaxies, seyferts, quasars, blazars are different manifestations of the same kind of object with the difference being due to the relative orientation of an accretion disk (and jet), surrounding a supermassive black hole, with the line of sight. The most interesting class of AGN are blazars, which are thought to be AGN with the axis of the jet pointed towards the observer. One of the prominent characteristics of AGN is variability in flux and polarization properties at various timescales ranging from minutes to years. The study of variability, is one of the important tools to probe the inner regions of AGN. Variability at short timescales provide constraints on the size of the emitting region and the mass contained within that region. Thus important physical characteristics of the central engine can be obtained by studying the variability pattern of the AGN. Blazar OJ287 is thought to be a two black hole system based on the long term periodicity noticed in it's light curve. A smaller supermassive black hole with a mass of only 100 million MSun orbits the larger one with an observed 11-12 year orbital period as inferred from nearly periodic variation of 11-12 years. We have been monitoring OJ 287 over a long time using the 1.2m telescope with LN2 CCD at Mount Abu IR Observatory (MIRO). In the present work we shall discuss some results from the 2012-2013 observing season.

ASI 2016 – Abstract Book 124

EA-33 ASI2016_737 Chayan Mondal Poster

A. Subramaniam, K. George, Indian Institute of Astrophysics, Bangalore- 560034

Star formation in the spiral galaxy NGC 300

NGC 300 is a SA(s)d type galaxy in the sculptor group of galaxies at a distance of 2 MPc. It has a good inclination to study propagation of star formation. Since UV radiation can probe the recent activities, we have used the GALEX data in the FUV and NUV channels for this study. We used the FUV-NUV colour to derive the ages and for this, we generated diagnostic diagrams for GALEX colour with the help of starburst99 model. From the model we created color (FUV-NUV) vs age (1 to 900 Myr) dependency for different metallicities (Z= 0.04, 0.02, 0.001) assuming instantaneous star formation for an IMF 2.35. Considering an interstellar reddening (E(FUV-NUV)= -0.564) and observed metallicity (Z=0.02) of NGC 300 into account we have converted the observed color distribution to an age distribution. The result clearly shows that most of the young stellar populations are present close to the centre of the galaxy and also along the spiral arm. We present the results of this study here.

EA-34 ASI2016_752 Nimisha Kantharia Poster

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Counter-rotation in galaxies

Counter-rotation has been observed in galaxies with morphologies ranging from elliptical to spiral to irregular and in galaxies which are isolated to interacting. Both factors - internal and external to the galaxy have been invoked to explain this peculiar and intriguing observed phenomenon in galaxies. In this paper we discuss a few cases and suggest a modified model to explain the observed counter-rotation in interacting galaxies.

EA-35 ASI2016_753 Ishwara Chandra CH Poster

Sebastian, Biny and Ishwara-Chandra CH NCRA-TIFR

Discovery of a giant radio galaxy with GMRT

We have discovered one of the largest and distant giant radio galaxy in the field of Lynx, from the deep GMRT 150 MHz observations. It is located at a redshift of 0.6 and has a linear size of 2.2 Mpc. Large sized radio sources at these redshifts are important to understand the evolution of radio sources, confinement of lobes and bridge by inter-galactic medium, radiative lifetime and possible re-acceleration scenarios in bridges that makes them radiate for longer duration. In this redshift range, only a few radio sources are known to have such large linear size. Here we present multi-frequency GMRT data of this source and spectral ageing analysis.

ASI 2016 – Abstract Book 125

EA-36 ASI2016_767 sameer Poster

K.S.Baliyan,Physical Research Laboratory Navpreet Kaur, Physical Research Laboratory S. Ganesh, Physical Research Laboratory

Decade long optical monitoring of Blazar 3C66A

Blazars are radio loud AGNs with their relativistic jets pointed close to line of sight of the observer boosting their emission due to relativistic beaming. They show rapid and strong variability spanning the entire electromagnetic spectrum, high and variable polarization in radio and optical regimes and dominant non thermal emission from radio to high energy gamma-rays. These also show long term variations with varying time scales. It would be interesting to see if the short term variations have any relationship with the long term trends. Keeping this in mind, we have been monitoring a set of blazars from Mt Abu IR Observatory (MIRO) for more than 10 years now. In this presentation, we would like to discuss this program, with specific study of BL Lac Object 3C66A. The monitoring of blazar 3C66A, from 2005 November 06 to 2015 October 23, in the BVRI broad bands using 1.2m telescope of MIRO was carried out using LN2 cooled CCD. Blazar 3C66A exhibited significant variations in optical flux on short and long term time scales. However it showed a IDV duty cycle of about 16% only. Our statistical study, using structure function, discrete correlation functions and L-S periodogram suggests time scales of intra- night variability from ~ 30 min to about 3.5 hours, and, in at least one case existence of quasi-perodic oscillations with a period of ~ 30 min. The IDV amplitudes in R-band were found to vary from 0.02 mag to as high as 1.1 mag. The typical rate of flux variation was estimated to be ~0.06 mag/hr in both the rising and falling phases. The shortest timescale of variation results in setting an upper limit of 8.1 x 10 14 cm for emitting region size and about 4.3 x 108 Msun as mass of black hole. The long-term study suggests a mild bluer-when- brighter behaviour, typical for blazars, with a large number of short term flares superimposed on the slowly varying brightness flux. The long-term study also gives an indication of a periodicity of about 2.48 years but large gaps in the data forbid us to state it confidently.It means that every 2.48 years, a major flare occurs in the jet, caused by, perhaps, fresh injection of plasma in the jet. Another interesting aspect of the long term study reveals, though not strong, larger intra-day variability amplitudes during the nights when the source is relatively fainter. Normally, one would expect high variability activity with larger amplitude of variation during the bright, flaring phases of the source when highly turbulent jet plasma is expected to interact with frequent shock formations leading to its rapid acceleration and subsequent radiative cooling. More data are required to arrive at a better analysis of the long term behavior of blazar 3C66A.

ASI 2016 – Abstract Book 126

EA-37 ASI2016_771 Narendra Nath Patra Poster

Jayaram N. Chengalur, NCRA-TIFR

Dark galaxies and their dark matter content

The long standing 'missing satellite' problem is one of the few hard challenges which poses significant difficulties in our understanding of galaxy formation and evolution under Lambda-CDM cosmology. The number of low mass galaxies predicted by Lambda-CDM, is far more in numbers than observed. Recent deep surveys (optical and radio) have started detecting very faint galaxies though, the discrepancy largely remains. Possibilities could be, the Lambda-CDM prediction is incorrect, or the galaxies are not forming stars efficiently to be detected by our observation (dark: dark galaxies/clouds). In the absence of star formation, these galaxies could be detected in HI and large surveys are planned in several leading radio telescopes to hunt these dark galaxies. Due to very similar gas properties and their proximity to large galaxies (hierarchical structure formation model), dark galaxies very often confused with Compact High Velocity Clouds (CHVCs). In fact, many of the suspected dark galaxies are ruled out due to their proximity to large galaxies. Existence of an associated dark matter halo with dark clouds can be used as a strong indicator of its cosmological origin. We solve hydrostatic equilibrium equation and reconstruct column density and velocity dispersion profiles of dark clouds in the presence and absence of a dark matter halo and demonstrate that inspecting the observable MOMNT profiles it is possible to identify a dark galaxy with associated dark matter halo. Further, we show that the dark matter density structures also could be recovered by cross-matching the MOMNT profiles using Monte-Carlo simulations.

EA-38 ASI2016_772 Peter Kamphuis Poster

T. Day B. S. Koribalski P.Serra G.Heald S. Haan affiliation is CSIRO Astronomy & Space Science, Australia for all.

Neutral Hydrogen in the Halo of the Early Type Galaxy ESO 92-G021

The haloes of spiral galaxies connect their inner disks to the inter galactic medium. Additionally they can serve as reservoirs of baryonic matter that can replenish the the star forming gas in the discs of galaxies. However, these haloes are hot with very long cooling times. Recent modelling shows that the cold gas in the halo, expelled by star formation in the disc, can serve as an catalyser in cooling down the hot halo. This makes the disc halo-connection a crucial element in understanding galaxy evolution and the continued star formation in spiral galaxies. Up to now research in this field has focussed on spiral galaxies, in which extra-planar cold gas has been observed often. However, in the last decade it has become clear that many that Early Type Galaxies (ETGs) also contain significant fractions of HI. As the star formation history of ETGs is significantly different from spiral galaxies provide an excellent opportunity to study the disc-halo connection from a completely new angle. One such ETG, ESO 92-G021, has been found to have a comparatively high rate of star formation and an extended, regular HI disk. In order to study whether this galaxy contains extra-planar neutral hydrogen we have obtained deep observations with the Australia Telescope Compact Array. Here we will show a detailed kinematical analysis of the HI disc in this galaxy. The model constructed in this analysis will enable us to separate the gas in the disc from any extra-planar gas that is present.

ASI 2016 – Abstract Book 127

EA-39 ASI2016_783 Navpreet Kaur Poster

Navpreet Kaur (PRL), Sameer (PRL), Sunil Chandra (TIFR), KS Baliyan (PRL), S Ganesh (PRL) PRL:Physical Research Laboratory, Ahmedabad, India TIFR:Tata Institute of Fundamental Research, Mumbai, India

Multiwavelength study of recent flaring activity in HBL 1ES 1959+650

Since the central engine, responsible for huge energy output, of AGNs is too compact to be spatially resolved with today's facilities, variability in flux across the electromagnetic spectrum play a crucial role in understanding the structure of these sources and the physical processes responsible for their emissions. We observed relatively less studied high energy peaked blazar, 1ES 1959+650, from Mt Abu 1.2m telescope during October - December 2015 in optical. The source has shown tremendous activity in X-ray and Gamma- rays as reported via several Astronomical Telegrams. In X-ray, it seems to consistently break earlier records with brightest ever state with 22.97 counts/s (equivalent flux 9.35 times 10^{-10} erg cm{^-2} s^{-2}) on 26 December 2016 (Atel# 8468). The activity started first in high energy gamma-rays which was immediately picked up at lower energies: X-ray and UV - optical. In optical R band, 1ES 1959+650 brightened from 14.30 (October 23, 2015) to 14.10 (November 18). It reached R~ 14.05 mag on December 5, 2015. Since then, it has gone fainter as per our observations upto December 14. We have also monitored the source for more than two hours over few nights to check for intra-night variability but it was not found very significant (< 3-sigma level). To understand multiwavelength behaviour of the source during the flare of October - December 2015, we have analysed X-ray, UVOT (Swift) and Gamma-ray (Fermi) data for the period. Preliminary results show strong correlation between all the light-curves corresponding to R-band, UVOT bands, X and gamma-ray flux. The main outburst, starting at about MJD 57270 appears to be half-way albeit seems to have peaked. The details of the study will be presented at the meeting.

ASI 2016 – Abstract Book 128

EA-40 ASI2016_807 Shubham Srivastav Poster

G. C. Anupama (IIA) D. K. Sahu (IIA)

PSN J15053007+0138024 : a faint transitional type Ia supernova.

Optical observations of type Ia supernova (SN) PSN J15053007+0138024 obtained at the Himalayan Chandra Telescope, spanning a phase of $-5$ to $+140$ days since $B$-band maximum are presented. The SN reached $B$-band maximum on JD 2457113.3, at a peak apparent magnitude of $m_B = 13.99 \pm 0.02$. The SN showed a fast post-maximum decline in luminosity. The decline rate parameter in $B$-band was measured to be $\Delta m_{15}(B) = 1.71 \pm 0.04$. Adopting a distance modulus of $\sim 31.6$ mag for the host galaxy NGC 5839, the peak absolute $B$-band luminosity is $\sim -17.9 \pm 0.2$ after correcting for Milky Way reddening, making it fainter than what is expected from the width-luminosity relationship. Fitting an analytical model to the quasi-bolometric light curve of the SN indicated that a total of $\sim 0.70$ M$_{\odot}$ was ejected, whereas $\sim 0.20$ M$_{\odot}$ of $^{56}$Ni was synthesized in the explosion. The spectra indicated a rapid velocity evolution as measured from the Si~{\sc ii} $\lambda 6355$ feature, with a velocity gradient of $\sim 100$ km/sec/day between +0 and +10 days since $B$-band maximum. The rapid velocity evolution, along with the fast decline rate places this event in the FAINT subclass (Benetti et al. 2005), whereas the equivalent widths of Si~{\sc ii} features close to $B$-band maximum place the event in the Cool (CL) subclass (Branch et al. 2006) among Ia supernovae (SNe). Although the absolute luminosity of this event is closer to the sublumious 1991bg-like class of SNe Ia, other photometric and spectroscopic properties - like the secondary peak in the $I$-band light curve and the absence of Ti{\sc ii} features in the early spectra place it closer to normal SNe Ia. This event is thus classified as a transitional Ia, with properties intermediate to normal and subluminous SNe Ia.

ASI 2016 – Abstract Book 129

EA-41 ASI2016_822 Sushma Kurapati Poster

Jayaram N Chengalur, National Centre for Radio Astrophysics - TIFR

Dark and visible matter in gas rich dwarf galaxies

We present the Giant Meterwave Radio Telescope (GMRT) observations of two gas rich dwarf galaxies J0626+24 and KDG192 in the HI 21 cm line. J0626+24 is a void dwarf galaxy located in Lynx-Cancer void. The HI velocity fields for both the galaxies are regular and show systematic pattern that is consistent with the rotational motion. However, for both the galaxies, velocity fields show kinematical asymmetry between two halves of the galaxy. We derive the rotation curves using tilted ring model and fit mass models to them. Mass modelling of both the galaxies show that, they can be well fit with either a modified isothermal halo or a NFW halo. For both galaxies, in the case of NFW halo, the concentration parameter obtained using best fit differs significantly from the expected concentration parameter(from the scaling relations for LCDM models). We compiled a set of dwarf galaxies from the literature, compared their dark matter halo properties to the void dwarf galaxy(J0626+24). We find that parameters of dark matter halo of void galaxy don't deviate from the distribution of dwarf galaxies in high density regions. We also find that the rotation curves derived using Modified Newtonian Dynamics (MOND) also provide reasonable fit for both the galaxies. But the critical acceleration parameter obtained from the MOND fits, differs from the critical acceleration parameter expected from MOND theory.

ASI 2016 – Abstract Book 130

EA-42 ASI2016_823 Pradeepta Kishore Mohanty Poster

Ananda Hota (UM-DAE CBS, Mumbai & RAD@home, India), Chiranjib Konar (Amity University, Noida, India), Pradeepta Mohanty (RAD@home, India), Megha Rajoria (RAD@home, India), Pratik Dabhade (RAD@home, India), Sravani Vaddi (RAD@home, India), Alakananda Patra (RAD@home, India), Sagar Sethi (RAD@home, India), Charitarth Vyas (RAD@home, India), Arpita Misra (RAD@home, India), Lavanya Nemani (RAD@home, India), Chhaya Verma (RAD@home, India), Anjali Amesh (RAD@home, India), Shilpa Dubal (RAD@home, India), Karuna Gamre (RAD@home, India), Mitali Damle (RAD@home, India), Akash Mantri (RAD@home, India), Vrunda Maniya(RAD@home, India) et al.

Reporting Discoveries from GMRT by RAD@home citizen-scientists using complete TGSS DR5 data

The geographical non-uniformity of astronomical research institutes suggests an unequal opportunity in accessing those central facilities when we consider students and citizens not pursuing PhD. Public outreach programmes and undergraduate projects are only ways to inform and inspire students. One powerful way to alleviate such socio-economic and geo-political constraints on inclusive growth with equal opportunity to all citizens is use of Internet. Three years ago (April 2013) RAD@home (#RADathomeindia #ABCDresearch), first Indian Citizen-science research project in astronomy was launched in Google and Facebook asking science-educated citizens (any BSc/BE) irrespective of their status, student/employed/unemployed, to participate by making UV-Optical-IR-radio multi-wavelength RGB color images of galaxies and radio galaxies using NASA Skyview which were shared and discussed by all participating members (over 1600 strong till date) on Facebook. Those found good were declared RGB-qualified and further called to get trained in one week RAD@home Discovery Camps, held at various host institutions all over India namely IOP (Bhubaneswar), HRI (Allahabad), UM-DAE CBS (Mumbai), Nehru Planetarium-Vigyan Prasar (Delhi)). During the camp, apart from normal astronomy lectures, citizen-scientists discover potentially new radio sources seen in the TIFR GMRT Sky Survey (TGSS) images. As TGSS images at 150 MHz were of the best resolution and sensitivity at such low radio frequencies, in every camp they have discovered cosmic sources that is worth follow up investigation by professional astronomers. GMRT Time allocation Committee (GTAC) has awarded observing time, going through standard international competition, for three cycles in a row. This programme named, GOOD-RAC: GMRT Observation of Objects Discovered by RAD@home Astronomy Collaboratory, has been appreciated by SKA-India consortium as a successful model and RAD@home appeared in the international ARAA-review paper on citizen-science in astronomy. The e-Astronomers (approx 50) trained during the camps continue to work from home, facilitated with three hours of online class a week across the country. Observational results so obtained by these e-astronomers will be presented in this meeting. Our results include, several new episodic radio galaxies, Speca-like spiral-host star-forming exotic radio galaxies, bent-lobe radio galaxies sitting in new galaxy filaments, dead-lobe radio galaxies, relic/halo diffuse radio emission in clusters of galaxies. The list of each type of objects has grown up significantly since last ASI meeting in Pune. Now, we have completed analyses of TGSS(DR5) image files and our journal paper is getting ready for submission, certainly before the meeting. Since characterizing diffuse emission in multi-frequency and angular-scale-sensitive interferometric images can be better done by human than computer algorithm, RAD@home will continue to compliment professional research in TMT-SKA era.

ASI 2016 – Abstract Book 131

EA-43 ASI2016_828 Naseer Iqbal Poster

Tabasum Masood and Nasser Demir

Entropy Change and Phase transitions in an Expanding Universe

The work complies a correlated study of a gravitational quasi-equilibrium thermodynamic approach for establishing and signifying a unique behaviour of the cosmological entropy and phase transitions in an expanding universe. On the basis of prescribed boundary conditions for the cluster temperature a relation for the intra cluster medium(ICM) of galaxy clusters have been derived. A more productive and signifying approach of the correlation functions used for the galaxy clustering phenomena shows a unique behaviour of the entropy change where a phenomena known as the gravitational phase transition occurs. This unique behaviour occurs with a symmetry breaking from mild clustering to low clustering and from mild clustering to higher order clustering which differs from a normal symmetry breaking in material sciences. We also derive results for the specific latent heat associated with the phase transitions of 3.20Tc and 0.55Tc, for the mildly clustered phase to the low clustered phase and from the mildly clustered phase to the highly clustered phase, respectively.

EA-44 ASI2016_848 Prasad Subramanian Poster

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Episodic blobs in AGN jets - analogies with solar CME initiation

The manner in which jets are launched from the accretion disk systems around active galactic nuclei and microquasars is still ill-understood. While there has been some progress in understanding the origin of a steady Poynting flux dominated outflow, the origin of episodic, particle dominated blobs is still unclear. We will apply ideas used to explain the initiation of coronal mass ejections from the Sun via Lorentz forces. In particular, we will investigate the applicability of a specific (ideal MHD) expansion instability that can explain the ejection of blobs.

ASI 2016 – Abstract Book 132

EA-45 ASI2016_849 Namrata Roy Poster

Dr. Ritaban Chetterjee Presidency University

Properties of Gamma-Ray and Optical Outbursts of Fermi Blazars

A large database of blazar variability is being built through Fermi and supporting multi-wavelength observations during the last seven years. These data regularly have a time resolution of a day and sometimes of hours. We analyze the Fermi-LAT and SMARTS R-band light curves of a large sample of blazars to study the symmetry of the outbursts, i.e., if those have similar rise and decay timescales. We find that longer-timescale (greater than 10 days) outbursts are symmetric while some of the short-timescale (less than 1-2 days) flares are asymmetric. We use a numerical model of non-thermal emission in blazar jets to investigate the possible cause of this asymmetry in short-term outbursts other than the obvious reason, namely, faster acceleration and slower cooling. These include specific location of the relevant emission region(s) in the jet w.r.t. our line of sight, and strength of the external photon field. From this we can probe the radiative loss timescales in blazar jets and find out other related parameters.

EA-46 ASI2016_857 Biny Sebastian Poster

Dharam V. Lal, NCRA-TIFR

Imaging results from GMRT wideband backend

As a part of the upgrade of Giant Metrewave Radio telescope (uGMRT) process, data for two radio galaxies 3C129 and 3C285 was acquired with the uGMRT using the new 300-500 MHz feeds and the new GMRT wideband backend (GWB) from 16 antennas system. The GMRT software backend data with a bandwidth of 32 MHz at 325 MHz was also recorded, and was analysed and compared with the GWB data. Continuum imaging results from this exercise will be presented.

ASI 2016 – Abstract Book 133

EA-47 ASI2016_861 Yogesh Wadadekar Poster

Sandeep Sirothia (SKA-SA, NCRA-TIFR), Aritra Basu (MPIfR, Germany), Veeresh Singh (PRL), C. H. Ishwara-Chandra (NCRA-TIFR), Alexandre Beelen (IAS, France) and Alain Omont (IAP, France)

A GMRT survey of some Herschel/HerMES deep fields at 325 MHz

Deep radio observations of well studied fields at far infrared and other wavelengths are effective tracers of obscured star formation and active galactic nuclei over a wide range of redshift and luminosity. FIR observations suffer from large positional uncertainty, while radio observations yield accurate positions, and therefore, enable unambiguous identification of optical counterparts, particularly for dusty high-z galaxies, and thus eventually leading to measurement of redshifts. The abundance of multiwavelength imaging and spectroscopy in these deep fields enables detailed studies of the physical phenomena underlying the radio sources. We have carried out a systematic program to observe 3 fields viz. the XMMLSS field, the Lockman hole field and the ELAIS-N1 field to depths of upto 100 micro-Jy rms over about 40 deg^2 with the GMRT at 325 MHz. I will discuss the comprehensive scientific exploitation of the data in the XMMLSS field that has led to advances in the study of distant radio AGN, of the radio-FIR correlation in normal star-forming galaxies up z ~ 1 and to the discovery of a dying, giant radio galaxy at z ~ 1.3.

EA-48 ASI2016_917 Brajesh Kumar Poster

G. C. Anupama, D. K. Sahu, S. B. Pandey, S. Srivastav, V. V. Sokolov, A. S. Moskvitin et al.

Optical study of Type Ic supernova 2011jm

We present optical photometric and low-resolution spectroscopic observations of a bright (~14.8 mag) Type Ic supernova (SN) 2011jm. This transient was discovered in public images of the Catalina Sky Survey in galaxy NGC 4809. The photometric follow-up (UBVRI broad-bands) of SN was performed using various telescopes in India and Russia. These observations are distributed over 40 epochs covering a total span of about 6 months. The optical low-resolution spectroscopic data were acquired using 2m HCT and 6m SAO telescopes at 7 epochs. We further obtained single epoch polarimetric data (in I-band) of SN using AIMPOL instrument at ARIES telescope. The SNID fittings and light curve investigations indicate that discovery of this event was relatively late (2-4 months after maximum light). The magnitude decay rate in V and I bands are similar while it is highest in B band. Here, we will also present various explosion parameters (e.g. Ni mass, explosion energy and photospheric velocity etc.) along with the polarization results.

ASI 2016 – Abstract Book 134

EA-49 ASI2016_962 Abhidnya Thakur Poster

Dr. Sunil Chandra, POST DOCTORAL FELLOW, Tata Institute of Fundamental Research (TIFR), Mumbai.

Study of Gamma ray flares from Blazar PKS 1424-41

The Blazar is a type of an active galactic nucleus (AGN) whose relativistic jet oriented along our line of sight. They are highly energetic in nature, emitting in all bands of electromagnetic spectrum. Blazars are rare objects in the universe as they emits in GeV and TeV range (Gamma ray band), which makes their study important. Hence we are studying blazars in high energy band. In this work we present detailed analysis of Fermi Blazar PKS 1424-41 between June, 2012 to August, 2014. For this purpose we used the data of Fermi Large Area Telescope (LAT). Variability and Spectral Energy Distribution (SED) are important tools to study mechanism of physical processes responsible emission from Blazars. Hence we studied the lightcurves and SEDs for individual flares. Blazar PKS 1424-41 exhibit five major gamma ray flares of different flux value along with number of subflares in it. All five flares peaked almost in equal interval from each other. We also studied two small flares and quiescent period of PKS 1424-41. The nature of flares is complex with many showing sharp rise and slow decrease. Here we are using leptonic model to represent SEDs which includes inverse Compton emission. Detailed study of Blazar PKS 1424-41 will be helping us to understand the insights of this class of AGNs.

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ASI 2016 – Abstract Book 135

ASI-2016 Poster Presentations

Instrumentation and Techniques

IT-1 ASI2016_1038 Ajaz Ahmad Dar Poster

Ajaz Ahmad Dar1 and Manzoor A. Malik2 1Islamia College of Science and Commerce, Srinagar, J&k, India 2Department of Physics,University of Kashmir,Srinagar-190006, J&K, India

Site Survey of Gulmarg, Kashmir, India for Optical Astronomical Observations

The site survey of Gulmarg Kashmir at altitude of about 9000 feet above sea level is based on analysis of meteorological conditions cloud cover, temperature, wind speed, wind direction, relative humidity and atmospheric pressure etc. Analysis and characterization of meteorological conditions suggests that Gulmarg, Kashmir is a potential site for carrying out photometric as well as spectroscopic observations of celestial objects i.e., galaxies, star clusters, gamma ray bursts and particularly study of variable stars etc.

IT-2 ASI2016_444 Mithun N P S Poster

S. V. Vadawale, T. Chattopadhyay, S. K. Goyal, A. R. Patel, Physical Research Laboratory, Ahmedabad

Characterizing scintillator with Si photomultiplier for Compton X-ray polarimeter

Scintillator detectors coupled with conventional photo-multipliers are being used in hard X-ray and gamma ray observatories since long. Now there is growing interest in scintillators coupled with silicon photo-multipliers (SiPM) for their potential use in spectroscopy, imaging and polarimetry in hard X-rays. With the use of new generation SiPM, it is now possible to bring down the lower energy threshold of scintillators to few tens of keV. In earlier work we have demonstrated successfully the use of CsI(Tl) scintillators read by SiPM in focal plane Compton polarimeter. To further improve the sensitivity of the polarimeter, the performance of different scintillators and SiPMs needs to be evaluated. In this context we characterize CsI(Tl) scintillator (5mm x 5mm x 15mm) read by SiPM at one end. We studied the detection probability for different incident photon energies as a function of distance from the SiPM. Geant4 simulations of X-ray interaction in scintillator and subsequent generation and transport of optical photons were carried out and was compared with the experimental results. How these results will help in deciding amongst the different scintillators and SiPMs and in arriving at optimum configuration will also be discussed.

ASI 2016 – Abstract Book 136

IT-3 ASI2016_489 Varun Kumar Poster

Padmakar Singh Parihar

An Inductive Edge Sensor for Segmented Mirror Telescope

Edge sensor is a vital component of any segmented mirror telescope (SMT) and their performances highly depend on the performance of edge sensor. In order to achieve very high spatial resolution and sensitivity, all mirror segments of SMT‟s must be precisely positioned with respect to each other to form a single primary mirror. Capacitance based displacement sensors are widely used for this purpose, but they have inherent sensitivity towards humidity and dust, which makes them unsuitable for telescopes installed at low altitude and humid regions. Whereas, inductance based sensors produce promising results in such situations. These inductance based sensors works on the principle of mutual inductance variation between two planar inductors. There are number of requirements for the sensor, such as very high sensitivity, temporal stability, immunity toward environmental changes, low noise as well as ability to probe more than one dimension. We have used COMSOL multi-physics for design and analysis of planar coils, required for inductive sensor. Effect of shape of the coil, trace geometry and density, number of coils in transmitter and receivers, current in the transmitters etc. are the design parameters deciding the sensitivity, range and sensing dimensions. The goal is to design and develop an inductive edge sensor which should have high sensitivity to piston, gap and tilt as well as having large sensing range with few nanometer precision. After optimizing the design, these coils are fabricated on flexible polyimide substrate by making use of classical PCB manufacturing technology. Flexible coils bonded on low thermal expansion glass blocks ensure very high thermal stability, which is one of the critical requirements for any edge sensor. In addition to the sensor, FPGA based sensing electronics has also been designed and developed. In this paper we report results related to sensor design and analysis, describe the sensor manufacturing process and related electronics. Finally we explain sensor calibration procedures and report preliminary results related to the performance.

IT-4 ASI2016_491 Hariharan Krishnan Poster

Hariharan Krishnan Indian Institute of Astrophysics

High Speed Digital Back-end for Observation of Low-Frequency Solar Radio Bursts

The Indian Institute of Astrophysics operates a low-frequency spectrograph system viz.Gauribidanur Low Frequency Solar Spectrograph (GLOSS)[1] operating in the frequency range 85-35 MHz located at the Gauribidanur Radio Observatory (about 100 km North of Bangalore, India). It is a phased array system of eight Log-periodic dipole antenna elements being operated in total power mode to record the dynamic spectrum over a period of 8 hours everyday. The GLOSS is primarily used for monitoring the radio transients from the solar corona which have a close association with flares and Coronal Mass Ejections (CMEs) from the lower layers of the Sun. The observatory also hosts a suite of other instruments (http://www.iiap.res.in/centers/radio) dedicated for regular observation of the radio emission from the solar corona in the afore mentioned frequency range which corresponds to a heliocentric distance of 1.2-1.8 solar radii in the solar atmosphere. A conventional sweep-frequency analyzer was used as the back-end for the spectrograph. As a part of the back- end upgrade process, a new digital back-end receiver based on high-speed ADC and FPGA data acquisition hardware was configured and tested with the spectrograph. The details of the hardware system along with trial observational results will be presented and discussed in the talk. ASI 2016 – Abstract Book 137

IT-5 ASI2016_493 Avinash Surendran Poster

Mahesh P. Burse, Inter-University Centre for Astronomy and Astrophysics, Pune A. N. Ramaprakash, Inter- University Centre for Astronomy and Astrophysics, Pune Padmakar Parihar, Indian Institute of Astrophysics, Bangalore

Scalable kernel for Adaptive Optics on FPGA

The main objective of the present project is to explore the viability of an adaptive optics control system based exclusively on FPGAs, making strong use of their parallel processing capability. The ability to access several hundred hard multipliers and the explicit customization of several logic gates concurrently in the FPGA allows for performance far beyond that of a modern CPU or GPU for tasks with a high level of parallelism and a well- defined structure such as Adaptive Optics (AO) control. The target of the current project is to generate a kernel for adaptive optics control based on a modification of the popular Matrix Vector Multiplication (MVM) technique wherein the system would be flexible to acquire and understand the signals coming from the various wavefront sensing techniques and to generate the signals for different modes of wavefront compensation. The system would be scalable with respect to the required degrees of freedom of AO and the size of the telescope. Preliminary Simulation Results for the formulation of the platform, and a design of a fully scalable AO reconstructor based on a lossless MVM compression technique will be presented. The ability of the platform to interface any generic memory, with an example of DDR3-SDRAM as the prototype for testing, will also be discussed. Some preliminary work on the wavefront processing unit interface and ideas for wavefront correction will also be presented.

IT-6 ASI2016_498 Ramya M Anche Poster

Ramya.M.Anche, G.C.Anupama, K. Sankarasubramanian, Asoke Kumar Sen Indian Institute of Astrophysics, Bangalore, Isro Satellite Center, Bangalore,Assam University, Silchar

Mueller Matrices of the Mirrors of the Thirty Meter Telescope (TMT)

The estimation of the Mueller matrices for all the three mirrors of the Thirty Meter Telescope (TMT) are presented here. The shapes of the primary, secondary and Nasmyth (M3) mirrors are concave hyperboloid, convex hyperboloid and a plane mirror (elliptical shape) respectively. In the case of primary and secondary mirrors, we have observed that some of the Mueller matrix elements repeat themselves within the azimuth angle (in degrees) 0- 90, 90-180, 180-270, 270-360. In other words, we see four different sectors within the above azimuth angle range, which further shows us no Instrumental Polarization (IP) or cross talk for on-axis rays at the prime focus and cassegrain focus. But after M3, we have observed that the matrix elements are no longer repeating in the four sectors. This is due the Nasmyth (M3) mirror kept at an azimuth angle which is a function of the zenith angle of the telescope, the Instrument Elevation Angle (IEA) and Instrument Bearing Angle (IBA) of the instruments placed on the Nasmyth platform. This work is important in determining the polarization capabilities of the Thirty Meter Telescope.

ASI 2016 – Abstract Book 138

IT-7 ASI2016_533 Shrishail Raut Poster

S.Sriram, IIAP P.K.Mahesh, IIAP Dr. Vineeth Valsan, IIAP

Modelling of warping forces for non-axial aspheric profile of thin mirror and a case study on cross coupling of warping forces on surface deformation. The TMT primary mirror is made of 492 hexagonal non axial-symmetric (aspherical shape) off-axis segments, each having a size of 1.44 m across corners. The TMT project prefers to utilize Stressed Mirror Polishing (SMP) of circular mirror blanks followed by hex-cutting, mounting onto a support system, and finally, Ion Beam Figuring (IBF). The SMP method has been proven to be the fastest and lowest cost polishing method for large aspherical mirror segments. Stress mirror polishing technique involves majorly optical-mechanical process in fabrication of mirror segments. In general, the idea is to apply an appropriate set of forces to a mirror blank so that after a sphere has been ground and polished into the blank, the forces can be removed, and the polished spherical surface deforms elastically into the desired non-axisymmetric surface. The thin mirror is modelled and analysed using NX Nastran. The set of warping forces applied on the thin mirror are generated depending upon the optical terms. The nodal displacement values of the mirror surface are further exported to MatLab software. Zernike coefficients of various optical terms and the simulated deformed mirror surface are generated in MatLab. Zernike coefficients obtained are compared with the corresponding theoretical values. Combinations for various optical terms are taken and analysed for any cross-coupling. We will be also taking single optical term at a time, the reason being that, so as to obtain the value of forces that are required to re- stress the mirror in order to obtain the desired value of the optical term at a time. The results of these simulation and modelling are discussed in this paper.

IT-8 ASI2016_609 Anwesh Kumar Mishra Poster

U.S. Kamath,IIA-Bangalore

Mid-infrared imager for the 2 meter Himalayan Chandra Telescope

Near infrared observations over the past decade have shown that the site of Indian Astronomical Observatory, Hanle is one of the best sites in the world. The high altitude (4500 meters), low temperatures and low precipitable water vapour content during most of the year make it a promising site for mid-infrared observations as well. We have designed various optical configurations for a mid-infrared imager with the twin goals of producing diffraction limited images and suppressing thermal backgrounds. After considering various challenges for implementation, we suggest the off-axis reflector design as the most suitable option. We present this design along with a brief listing of science cases.

ASI 2016 – Abstract Book 139

IT-9 ASI2016_622 Tanmoy Chattopadhyay Poster

Dr. Santosh Vadawale, Physical Research Laboratory, Ahmedabad, India Prof. A. R. Rao, Tata Institute of Fundamental Research, Mumbai, India Prof. Dipankar Bhattacharya, IUCAA, Pune, India Mr. Mithun N. P. S., Physical Research Laboratory, Ahmedabad, India

Generation of Response Matrix for multi-pixel CZT detectors

Cadmium Zinc Telluride (CZT) detectors have been the workhorse in hard X-ray astronomy for a decade now, implemented in many X-ray observatories e.g. SWIFT, NuSTAR and more recently in ASTROSAT. Response matrix for CZT detectors requires precise modelling of the X-ray lines as a function of energy. Instead of showing simple Gaussian feature, these lines exhibit a long tail at lower energies because of trapping of the charge carriers due to their low mobility (µ) and lifetime (τ). The effect is found to be more significant for high energy photons as the probability of charge loss increases with the depth of interaction. Therefore, precise line modelling in case of CZT detectors needs accurate measurement of µτ values for electrons and holes. For pixelated detectors, other significant components in the line modelling come from the crosstalk between the pixels due to charge sharing, fluorescence photons and Compton scattering. Charge sharing is expected to be quite significant making the CZT line profile further complicated. We have developed a numerical model taking into account all these physical processes to predict the CZT line shapes properly. The model is written in S-LANG and incorporated in spectral fitting package ISIS. Here we present the details of the numerical model and experimental measurements of mobility and lifetime of the charge carriers and the inter-pixel charge sharing fractions for 4 cm X 4 cm and 5 mm thick CZT detectors with pixel dimension of 2.5 mm X 2.5 mm, procured from Orbotech Medical Solutions (similar to the modules used in CZTI, Astrosat). In order to understand the charge sharing in the detectors in more detail, we did further experiments, results and implications of which will be discussed in this presentation.

ASI 2016 – Abstract Book 140

IT-10 ASI2016_627 Sireesha Chamarthi Poster

Ravinder K. Banyal, U. Lemke, S. Sriram, K. Ravi and Gajendra Pandey

Towards Radial Velocity Measurements with Iodine Absorption Cell on VBT Echelle Spectrograph

Instrumental drift is a major source of errors in high precision spectroscopy in astronomy. Changing environmental conditions at the observatory can cause a nightly drift in the spectrograph exceeding several 100m/s to few km/s. In addition, calibration errors may arise from different optical paths traversed by the reference beam (from arc lamps) and the star light. Note that, the two exposures are not simultaneous and results in spurious shifts as well as distortions in both the dispersion and the PSF due to spectrograph flexure, detector movement, and several other unknowns. A self-calibrating gas absorption cell placed in the light path can eliminate some of these errors. We are implementing the Iodine (I2) absorption cell technique to improve the radial velocity precision of our Echelle spectrograph attached to the 2.3m Vainu Bappu Telescope at Kavalur. The superimposed narrow I2 absorption lines allow us a) to model the instrument profile of the spectrograph and b) to extract the tiny Doppler shift in the stellar spectra. A high resolution template of the Iodine gas is required to accurately model the instrument profile of the spectrograph. We have used a Fourier Transform Spectrograph (FTS) facility of BARC at Mumbai to obtained a high resolution ( R> 100,000) scan of the gas cell. In this presentation, our completed work on mechanical design, temperature controller and hardware interface of the I2 cell will be discussed. We will also present our analysis of the I2 FTS data, relevant statistics and algorithm used for compiling a line list for the Kavalur spectrograph. Some preliminary results of solar spectra and bright stars observations with Iodine cell will also be discussed. Finally, we will give an outline of our approach to develop radial velocity analysis code for the Iodine cell.

ASI 2016 – Abstract Book 141

IT-11 ASI2016_691 Sabyasachi Chattopadhyay Poster

Sabyasachi Chattopadhyay, Pravin Chordia, A. N. Ramaprakash, Mahesh P. Burse, Bhushan Joshi, Kalpesh Chillal The Inter-University Centre for Astronomy and Astrophysics, Pune, India

IDSAC - IUCAA Digital Sampler Array Controller

IUCAA Digtial Sampling Array Controller (IDSAC) is a generic CCD Controller which is flexible and powerful enough to control a wide variety of CCDs and CMOS detectors used for ground based astronomy. It has a fully scalable architecture, which can control multiple CCDs and can be easily expanded. The controller has a modular backplane architecture consists of Single Board Controller Cards (SBCs) and can control a mosaic or independent of 5 CCDs. Each Single Board Controller (SBC) has all the resources to a run Single large format CCD having up to four outputs. All SBCs are identical and are easily interchangeable without any reconfiguration. A four channel video processor can process up to four output CCDs with or without dummy output at 1Mpixels/Sec/Channel with 16 bit resolution. Each SBC will have USB 2.0 interface which will be connected to a separate computer via USB to Fiber converters. The SBC uses a reconfigurable hardware (FPGA) as a Master Controller. The best feature of IDSAC is it uses the technique of Digital Correlated Double Sampling(DCDS). It is known that CCD video output is dominated by thermal KTC noise contributed from the summing well capacitor of the CCD output circuitry. To eliminate thermal KTC noise Correlated Double Sampling (CDS) is a very standard technique. CDS performed in Digital domain (DCDS) has several advantages over its analog counterpart, such as - less electronics, faster readout and easier post processing. It is also flexible with sampling rate and pixel throughput while maintaining the core circuit topology intact. The noise characterization of the IDSAC CDS signal chain has been performed by analytical modelling, software simulation and practical measurements. Various types of noise such as white, pink, power supply, bias etc. has been considered while creating a analytical noise model tool to predict noise of a controller system like IDSAC. Standard test bench softwares like Pspice and Multisim are used to simulate the noise performance while several tests are performed to measure the actual noise of IDSAC.The theoretical calculation matches very well with component level simulation as well as practical measurements within 10% accuracy.

IT-12 ASI2016_692 Anjali Yelikar Poster

Devansh Agarwal IISER Thiruvananthapuram, Pranshu Mandal IISER Thiruvananthapuram, Kanchan Soni IISER Thiruvananthapuram, Pratik Kumar IISER Thiruvananthapuram

An Undergraduate Dual-band Radio Interferometer

A two element dual-band intensity interferometer is built at IISER-Thiruvananthapuram by the undergraduates. The interferometer supports observations in C and Ku-band simultaneously with single polarization intensities and dual polarization intensities in both bands. The setup consists of commercially available C-band 1.8 meter satellite dishes and is assembled using affordable components, making it easily expandable and mobile. The interferometer has a baseline of 20 meters providing an angular resolution of 13' and 7' respectively for C and Ku-band. The individual dishes are calibrated using geostationary satellites in the C/Ku-band. The setup performs correlation of the intensities from the two dishes, discarding any phase information based on the Hanbury-Brown and Twiss effect. We developed a system for accurate telescope pointing, using sensors and simple electronics. With a sensitivity of 350 Jy in Ku-band, we aimed to detect and measure the flux of few radio sources and study their size and physical properties. We will present the results of our experiment here. We also discuss our plans and progress to develop an automated tracking system and use it to make an all northern radio sky visibility map at 4 GHz and 11.2 GHz. ASI 2016 – Abstract Book 142

IT-13 ASI2016_709 Ravinder K Banyal Poster

Ravinder K Banyal, Tanya Das, B. Ravindra and T. Sivarani

Development of a Fabry-Perot Wavelength Calibrator for High Precision Doppler Spectroscopy

There are two major challenges that need to be overcome for doing high precision spectroscopy. First is the spectrograph instability (zero-point drift) largely caused by slow temperature and pressure changes and second is to do with the limitations imposed by traditional calibration methods. The accuracy of the wavelength solution obtained from the emission lamps has serious drawbacks arising from the uneven line spacing, large intensity variations, limited wavelength coverage and spectral contamination from unknown sources. In this paper, we will present our work on proposed wavelength calibrator using Fabry-Perot (FP) interferometer to achieve a 1-10 m/s radial velocity precision. A large number of wide-band (500nm-650 nm) transmission lines of the FP will provide a highly stable and uniform frequency scale for a medium resolution (R~ 40000-60000) astronomy spectrograph. We also describe a frequency locking mechanism that we propose to control and eliminate the long term cavity drift by anchoring the complete transmission spectra of the FP cavity to an intrinsically stable fundamental atomic lines of the Rb-cell. In terms of stability and spectral coverage, FP calibrator is expected to reach a performance level of a laser frequency comb but with a significantly lesser cost and completely off-the-self components.

IT-14 ASI2016_710 Sreekanth Reddy V Poster

Sreekanth Reddy V, Ravinder K Banyal, P.Anbazhagan, R. Sridharan, B. Ravindra

Estimation of the atmospheric turbulence parameters using short exposure images with 1.3m telescope at Kavalur Atmospheric turbulence limits the ability of the ground based telescopes to form diffraction limited images. In order to develop high resolution imaging system, the estimation of the turbulence parameters, such as the Fried's parameter r0, isoplanatic angle, tilt-anisoplanatism between the objects and the coherence time are crucial. Turbulence parameters can be estimated by obtaining short exposure images with a high speed imager. In this paper, I will present our methodology and results of focal plane image motion of stars used to estimate the turbulence parameters with 1.3m telescope at Kavalur. A high speed camera (Princton, ProEM) was used to acquire bright star images of magnitude 6 or better in R band, for observations spanning nearly a year. Stars with different angular separations were chosen to estimate the image motion correlation in the telescope focal plane. We estimate the median r0 to be 12.5 cm ( seeing 1.3'' ). We also find that turbulence induced motion of the stars is strongly correlated (up to 75%) for pair of stars separated by 30''. These parameters will be used in designing a tip/tilt adaptive optics system for the telescope.

ASI 2016 – Abstract Book 143

IT-15 ASI2016_712 Anshu Kumari Poster

G.V.S. Gireesh, C. Kathiravan, Indian Institute of Astrophysics,Bangalore

CROSS-POLARIZED LOG-PERIODIC DIPOLE ANTENNA FOR LOW FREQUENCY SOLAR OBSERVATIONS The solar coronal mass ejections (CMEs) play a direct and vital role in deciding the space weather, so it becomes inevitable to study their dynamical properties in the lower corona (i.e., over the heliocentric distance range: 1.05 – 2 Rʘ; where Rʘ = radius of the solar photosphere) both prior to and after the eruption. Since the CMEs are magnetically driven and often associated with different kinds of non-thermal energy releases, one can use the latter to infer the properties of CMEs and to estimate the strength of the associated magnetic field (B). Cross-polarized Log-Periodic Dipole Antennas (CLPDAs), a combination of two mutually orthogonal log- periodic dipole antennas mounted on a common axis, can be used to observe B over a broad frequency range. But such antennas are a rare commodity because of the difficulties involved in fabricating them. We present here the details of CLPDA, designed and developed in-house at the Gauribidanur observatory, to observe the polarized radio emission from the solar corona in the frequency range ~ 50 – 500 MHz. The solar radio emission in the above frequency range originates typically over the heliocentric distance range: 1.05 – 2 Rʘ. The measured cross-talk between the two orthogonal antennas in the CLPDA was < -30 dB in the above frequency range with the VSWR < 2 throughout. Trial observations indicate that the degree of circular polarization (dcp) can be measured to an accuracy of ~98% with the above CLPDA. Also, few trial observations were used to determine the strength of the magnetic fields responsible for type – III solar radio burst emissions.

IT-16 ASI2016_714 Mayuresh Sarpotdar Poster

Jayant Murthy, Margarita Safonova Indian Institute of Astrophysics

Design and Development of a Star Sensor - StarSense

We have developed a star sensor (StarSense) for use in CubeSats to determine the satellite‟s attitude/orientation with an accuracy of 30". The sensor was designed in-house and comprises a Tessar lens which images the star field onto a radiation-hardened Star1000 CMOS detector with a MIL-grade Spartan-6 FPGA readout. The entire instrument was designed to minimize weight and power requirements. We chose the field of view of the sensor to be 10o with a limiting magnitude of 6.5m based on a sky simulation using the Hipparcos Bright Star Catalog. The requirement for attitude determination over the entire sky requires that we observe at least 3 stars in every field over the sky. One of the more challenging aspects of designing a star sensor is that it is intended for use in space and the algorithms must be fast yet without requiring much processing power. We have used the LEON SPARC v8 microcontroller which is rugged and fault tolerant to single event upsets and has an open source VHDL code. In StarSense we sequentially use Centroiding Algorithm, Geometric Voting Algorithm and QUEST Algorithm to process the acquired images and obtain the quaternion between the Inertial coordinate system and Sensor coordinate system. This quaternion is further passed on to the Attitude Control System of the satellite. We simulated these algorithms to estimate their performance parameters such as sky coverage, required memory, calculation speed etc.

ASI 2016 – Abstract Book 144

IT-17 ASI2016_730 Sachin S. Sherkar Poster

Nilesh S. Raskar (NCRA-TIFR) Dr. Dharam Vir Lal (NCRA-TIFR)

Testing of New wide-band backend of the upgraded GMRT: Current status and its long-term comparison with the existing software-backend Giant Metrewave Radio Telescope (GMRT) is world's most sensitive radio interferometer and is currently undergoing a very significant upgrade. One of the key objective of this upgrade is to improve sensitivity, e.g., by increasing the bandwidth of observations from present 32MHz to a target of 400 MHz, etc. In this regard, a new GMRT wide-band backend (GWB) is being developed and is being tested as well. Presently, end-to-end wide-band signal chain is now available on all GMRT antennas and GWB has been in use since February 2014. Here, we present 1) statistical long term stability analysis of the new wide-band system spanning this ~2 year long duration using existing GMRT software backend (GSB) as a benchmark, and 2) sensitivity differences between these two systems, existing GSB and new GWB.

IT-18 ASI2016_733 Nilesh Sadashiv Raskar Poster

Sachin S. Sherkar (NCRA-TIFR) Dharam V. Lal (NCRA-TIFR)

Testing the observing modes of upgraded GMRT: Current status tests and future plans

The Giant Metrewave Radio Telescope (GMRT) is undergoing a very significant up-gradation. The end-to-end broadband signal chain is currently available on all 30 GMRT antennas. An important feature of this upgrade is an increased observing bandwidth from existing 32 MHz to 400 MHz with 16k spectral channels. To achieve this, a next generation correlator, called GMRT wideband backend (GWB) is being developed, which supports several observing modes. Here, we present, these available modes for the GMRT users. We also present the data quality, e.g., stability, performance, etc. from GWB for these observing modes.

ASI 2016 – Abstract Book 145

IT-19 ASI2016_738 varun Poster

Varun, Raman Research Institute, Bengaluru, India. Rishin P. V., RRI . Gopala Krishna M. R., RRI . Biswajit Paul, RRI . Sandhya P., RRI . Nagaraja H. N., RRI .

A Large Area Photo-electron Polarimeter Technique : Experimental and Simulation Results.

Compact high energy sources under extreme magnetic and gravitational fields and anisotropic emission condition should produce polarized X-rays. Emission mechanism, magnetic field structure and physical geometry at source are crucial factors in determining Degree of polarization and polarization angle. The photo- electron X-ray polarimeters which image the tracks of X-ray photo-electrons in a gaseous medium have very high sensitivity for X-ray polarization measurements. However, for astronomical observations, these detectors require focusing optics as they have small dimensions. We are developing a large area X-ray polarimeter that will enable us to measure X-ray polarization without using focusing optics. Our technique uses proportional counters with closely spaced wires, interleaved as two set of anodes. This technique depends upon division of charges in photo-electron track among the two anodes. We have measured the charge division for 6 keV and 23 keV over a range of gas pressures. The pattern of charge division has a dependence on the angle between direction of wires and initial polarization direction of X-rays. We will present experimental and simulation result.

IT-20 ASI2016_743 Ajay Vibhute Poster

Prof. Dipankar Bhattacharya, IUCAA, Pune

Astrosat CZTI Image Reconstruction Techniques

India‟s first multi wavelength satellite Astrosat is employed with a hard X-ray payload Cadmium Zinc Telluride Imager (CZTI). CZTI uses a indirect imaging technique called Coded Mask Imaging. Here, we will describe results and methods used for Astrosat CZTI Image reconstruction. Also, we will compare results achieved by different techniques like Cross-Correlation, RichardsonLucy and Chi-square Matrix and the error in reconstruction for all the technique.

ASI 2016 – Abstract Book 146

IT-21 ASI2016_747 PRATIK KUMAR Poster

Devansh Agarwal,IISER Thiruvananthapuram Pranshu Mandal,IISER Thiruvananthapuram Kanchan Soni,IISER Thiruvananthapuram Anjali Yelikar,IISER Thiruvananthapuram

EVERYDAY RADIO TELESCOPE

Everyday Radio Telescope forms an accessible medium for observing radio sources. It is a commercially available telescope based on the satellite television receiving system. The telescope uses parabolic dish antenna for receiving radio signals. Here, in this project we designed Everyday Radio Telescope for observing the sun. We aimed to measure the Sun's brightness temperature at 11 GHz and-and the antenna beam width with our effective dish size 0.2177 square meters and sensitivity 0.5MJy.We currently measured the Sun's brightness temperature 13966.4K with an 8.6% uncertainty along with antenna beam width 3 degrees. Here we demonstrate how this small telescope can be used to measure the flux density from the solar observations and correlate them with presently available data. With the increased sensitivity we report the detection of Saturn and extended sources like the galactic arm of the Milky way.

IT-22 ASI2016_758 Jyotirmay Paul Poster

A. N. Ramaprakash1, Burse Mahesh1, Baranec Christoph2, Bui Khanh3, Chordia Pravin1, Das Hillol1, Dekany Richard3, Khodade Pravin1, Kohok Abhay1, Kulkarni Shrinivas3, Law Nicholas M4., Modi Deepa 1, Punnadi Sujit1, Rajarshi Chaitanya1, Riddle Reed3, Tendulkar Shriharsh3 1 Inter-University Centre for Astronomy & Astrophysics, Ganeshkhind, Pune 411007, India 2 Institute for Astronomy, University of Hawai„i at M¯anoa, Hilo, HI, NZ 96720-2700, USA 3 Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA 4 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA

Design and Development of IR Camera for Robo-AO

Adaptive Optics correction for atmospheric seeing works over a larger field of view at IR wavelengths than in optical. The Kitt Peak 2m telescope currently incorporates Robo-AO, which is a product of a collaborative effort between Caltech, USA and IUCAA, India. Robo-AO works with minimal overheads and provides good sky coverage. The first version of Robo-AO does not contain a high quality IR camera. To improve Robo-AO performance and scientific capabilities, an IR camera is being developed to accommodate 1arc min (radial) AO corrected field of view in J, H and K bands. The camera is being designed and built at IUCAA and will use a HAWAII detector procured by Caltech. This IR camera will help to correct overall atmospheric tip-tilt (low order aberration) in real time enhancing SNR for visible band science. It also works as a science instrument with tip-tilt correction signal provided by the visible camera. In this paper we describe salient features of optical & mechanical design, thermal load and development of IR camera for Robo-AO.

ASI 2016 – Abstract Book 147

IT-23 ASI2016_778 Ravishankar B T Poster

Dipankar Bhattacharya (IUCAA), Ramadevi M C (ISRO Satellite Centre), Seetha S (ISRO), Brajpal Singh (ISRO Satellite Centre), Anand Jain (ISRO Satellite Centre), Abhilash Sarwade (ISRO Satellite Centre)

ASTROSAT Scanning Sky Monitor: Data Processing and Analysis

Scanning Sky Monitor (SSM) on ASTROSAT is an assembly of three cameras working in soft X-ray band of 2.5 -- 10 keV, monitoring the sky for transient sources. The three Coded Mask cameras are mounted on a rotating platform and this assembly operates in stare-and-step mode. ASTROSAT was launched on Sep 28, 2015 and data from SSM ever since it was switched on on Oct 11, 2015 is being processed through a pipeline. This paper describes the steps involved in the data processing, coded mask imaging methods adopted, and discusses some results. A detailed account of the calibration results and first few months of data analysis & data products will be presented.

IT-24 ASI2016_797 Varun Bhalerao Poster

A. R. Rao (TIFR) Dipankar Bhattacharya (IUCAA) Santosh Vadawale (PRL)

First science from CZTI

The Cadmium Zinc Telluride Imager is a weide-field coded aperture mask instrument on Astrosat, sensitive to photons from 20 keV to over 200 keV. The science objectives of the CZTI include the measurement of curvature and reflection components in the spectra of Active Galactic Nuclei and X-ray binary systems, the study of Quasi-Periodic Oscillations at hard X- ray bands in accreting neutron star and black hole systems, cyclotron line spectroscopy of high mass X-ray binaries, the characterization of hard X-ray spectra of magnetars as well as the detection of gamma ray bursts and the study of their early light curves. CZTI is also capable of measuring hard X-ray polarisation for bright sources. I will discuss the first CZTI science results in several of these fields.

ASI 2016 – Abstract Book 148

IT-25 ASI2016_801 ANNU JACOB Poster

Padmakar Parihar, Indian institute of Astrophysics

Optics for Prototype Segmented Mirror Telescope

To get acquainted with segmented mirror technology and to develop a small telescope which can also be used for a few dedicated sciences, we have initiated a project to develop a prototype segmented mirror telescope (PSMT), of approximately 1.3m physical diameter. Seven identical hexagonal mirror segments with corner to corner length of 500mm, together constitute the primary mirror of the proposed telescope. Various measures have been undertaken to reduce the overall manufacturing cost of the prototype telescope, the important one being the use of spherical optics rather than aspheroid parabola/hyperbola. Initially we explored multiple methods used in the past to correct the spherical aberration introduced by primary mirror. However, finally we decided to correct spherical aberration by making use of ellipsoidal secondary as well as a combination of refractive optics placed near focal plane. PSMT optics has been designed by considering the primary mirror, both as a monolithic and as a segmented. The design was analyzed and it was verified that both approaches give similar image quality. Keeping several design constraints into consideration, telescope optics has been designed, which promises decent image quality for the narrow as well as wide field. The narrow field design offer image quality matching with the local seeing over an arc-minute field of view, without using any correcting optics. Whereas, wide field design require few small optics to correct remaining aberrations and provide good image quality over the field as large as 10 arc-minutes. Sensitivity and tolerance studies were carried out and the effects of manufacturing error on image quality were analyzed. Since primary mirror is made of segments and is driven by actuators, we also explored the possibility of improving off-axis image quality by providing additional tilt to outer mirror segments. In this work, we present our effort to design PSMT optics, which can be an option for the proposed large telescope.

ASI 2016 – Abstract Book 149

IT-26 ASI2016_834 Tejas Kale Poster

Pratik Dabhade, IUCAA; Madhuri Gaikwad, NCRA

Machine learning techniques for identifying large scale radio sources

Finding giant radio sources is still a process that relies heavily on diligent observation by the human eye. Typical procedure consists of going through large area radio maps to look for diffuse long emission. The results are reliable but slow. Additionally, this process cannot be employed to handle large radio survey data from LOFAR, TGSS, VLASS, etc. Hence, dire need exists to quicken the process by taking advantage of fast computers and advanced mathematical algorithms. But attempts so far to automate it have faced difficulty primarily owing to large, non-uniform sizes and relatively low surface brightness of these giant radio sources. Machine learning (ML) is the science of making computers learn without being explicitly programmed. Learning here refer to the process of fitting the best statistical model of a specified type in which the subject in question (response variable - continuous or ordinal) is modeled on a set of factors influencing the subject (explanatory variables - continuous or ordinal). Herein we will explore the applicability of two popular category of ML algorithms for classification of radio sources. The first is Artificial Neural Networks (ANN) for facial recognition wherein the algorithm makes its best attempt to split a source into mutually exclusive (latent) features. The other category is Logistic Regression, with attributes similar those used in handwriting recognition, in which we define a set of features like grayscale density, object dimensions, etc. whose distributions are useful for segregating different types of sources. In both the approaches, using a training dataset, the algorithm learns to associate a joint distribution of these features with each type of source. A test data is then used to determine the rate of misclassification of the model for each type of source to comment on its overall efficacy for wider application. For this purpose we choose NVSS radio maps to identify large scale radio sources. NRAO VLA SKY SURVEY( NVSS) is one of the best all sky radio survey till date. NVSS is a 1.4 GHz continuum survey covering the entire sky north of −40 deg declination (Condon et al 1998). Its images are made with a relatively large restoring beam (45 arcseconds FWHM) to yield the high surface- brightness sensitivity needed for completeness and photometric accuracy which is very essential in context of our project. Their RMS brightness fluctuations are about 0.45 mJy/beam = 0.14 K (Stokes I) and 0.29 mJy/beam =0.09 K (Stokes Q and U). The RMS uncertainties in right ascension and declination vary from < 1 arcseconds for relatively strong (S > 15 mJy) point sources to 7 arcseconds for the faintest (S = 2.3 mJy) detectable sources with a completeness limit is about 2.5 mJy.

ASI 2016 – Abstract Book 150

IT-27 ASI2016_856 Rishin Puthiya Veetil Poster

Gopala Krishna M.R., Biswajit Paul, Varun B., Duraichelvan R., Mohamed Ibrahim, Rajagopala G., Sandhya P., Mamatha T.S., Ezhilarasi M.S., Nagaraja H.N. Affiliation: Raman Research Institute, Bangalore

X-ray Polarimeter - POLIX: Design and development status

POLIX is an X-ray polarimeter being developed at Raman Research Institute (RRI) for a small satellite mission of ISRO. The instrument is based on Thomson scattering of X-ray photons from a low atomic mass scatterer and subsequent detection in X-ray proportional counters. It works in energy band of 5-30 keV. It will be suitable for X-ray polarisation measurement in about 50 brightest X-ray sources, with a Minimum Detectable Polarisation (MDP) of 2-3%. The accretion powered X-ray pulsars, black hole X-ray binaries, rotation powered pulsars, non-thermal SNR and AGNs will be the prime targets for this mission. A laboratory model of the instrument has been made and tested successfully, an engineering model has been designed and fabrication of the same is in the final stages. Tests towards engineering model qualification are in progress. We present different aspects of the instrument design, sensitivity for polarisation measurement, current status of development and qualification test results.

IT-28 ASI2016_859 Gopala Krishna M R Poster

Rishin P.V., Biswajit Paul, Varun B., Duraichelvan R., Mohamed Ibrahim, Rajagopala G., Sandhya P., Mamatha T.S., Ezhilarasi M.S., Nagaraja H.N., Pooja Verma and Affiliation: Raman Research Institute, Bangalore

X-ray Polarimeter POLIX: Signal Processing Electronics development

We describe the signal processing electronics for the Thomson X-ray polarimeter. The main requirement for the X-ray polarimeter is to determine the degree and the direction of polarisation of the incoming X-ray photons impinging on the detector. This requires finding out the position at which the photons are absorbed in the X-ray detectors. The electronics system amplifies the charge pulses from the detector, checks for the anti- coincidence so as to reject the charge particle background, digitises the peaks of the pulses at the two ends of the resistive wire and finds out the position of the incoming photons from these measurements using the principle of charge division. The electronics also time stamps the X-ray events data, packages it and stores it so as to transfer to the satellite bus. Apart from the signal processing section, the electronics also has the high- voltage section for biasing the detectors, a house-keeping system for monitoring the status of the entire payload and a telecommand system to command and control the payload from the satellite. All the signal processing operations are carried out using FPGA's. Different aspects related to design and development of the system along with the test results obtained will be presented.

ASI 2016 – Abstract Book 151

IT-29 ASI2016_864 Mohana Krishna.R Poster

Dr.Sankarsubramanian.K ISRO Raja Bayanna - USO Dr.Shibu Mathew - USO Dr. Ashok - ISRO Sowmya.H.K - ISRO Kumar - ISRO

Multi Slit Spectro-polarimeter – a high cadence solar spectro-polarimeter

A Multi-slit Spectro-polarimeter (MSSP) has been developed at the Space Astronomy Group of ISRO Satellite Centre for high cadence magnetic field observation of solar atmosphere. MSSP is designed to perform spectroscopy and polarimetric studies for simultaneous observation of the photosphere and chromosphere using Fe I 630.2nm and HeI 1083 nm respectively. With five slits scanning the FOV simultaneously, the achieved time cadence would be five time better than a single slit configuration. The instrument consists of a blazed grating with the blaze angle optimized for Fe I and He I lines. As the grating works at high orders and the usage of multi-slit, a DWDM type filter is used as the filter rather than the conventional order separation filters. DWDM filters have a flat-top response with a FWHM bandwidth of 6 angstrom. This filter is very sensitive to tilt and f-ratio of the input beam. An f-20 or slower beam gives satisfactory response. Laboratory tests were done on scanning mechanisms which is used to scan the image across the slit and found that a complete FOV can be covered in 2min. However, this would be dependent on the exposure time and the required signal-to-noise ratio. Spectrograph‟s spectral resolution is expected to be better than 30 milli- angstrom and from experiments it is found to be 26 milli-angstrom. Spectral dispersion of the system was found to be 10 milli-angstrom per pixel. This instrument is being placed as a back end instrument for the Multi Aperture Solar Telescope (MAST) at Udaipur Solar Observatory (USO). MAST is a 50cm off axis telescope installed at USO and was commissioned in the month of September 2015. The current engineering run is to achieve spectroscopy in 630.2nm line which will then be extended to polarimetry mode in future runs. This run is aimed at achieving the proposed spatial and temporal resolution. Preliminary results related to the engineering run will be discussed and the parameters like spatial, spectral resolution will be estimated from this run. The spectroscopic performance of this instrument in the actual field station will be discussed in this paper.

IT-30 ASI2016_888 Ashish Mahabal Poster

Varun Bhalerao (IUCAA), Akshat Singhal (IUCAA, Gran Sasso Science Institute), Sumeet Kulkarni (IUCAA, IISER), Andrew Drake, S G Dorgovski (Caltech), Eric Christensen, Steven Larson, Ed Beshore (LPL), Matthew Graham, C Donalek (Caltech), Ajit Kembhavi (IUCAA)

Deep stacked images and catalogs from Catalina Sky Survey

The 0.7m Schmidt telescope on Mt. Bigelow is part of the Catalina Sky Survey (CSS) and has been obtaining images with its current 2.8x2.8 sq. degrees CCD since 2003. It covers ~25000 sq. degrees hundreds of times, with a total of almost a million images. The images are currently served from IUCAA in the form of 5'x5' cutouts. The utility of these images - by themselves and in a stacked, co-added form - to current and future time-domain studies is immense. The stacking operation has recently been carried out. The stacked images go up to 3 magnitudes deeper. We present here the stacked image as well as the details of the process adopted, including the comparison of various state-of-the-art stacking softwares. From the resulting images we have extracted a deep catalog. While the catalog is not uniform, the depth makes it an excellent resource during transient searches including the ones for EM-counterparts of Gravitational Wave events.

ASI 2016 – Abstract Book 152

IT-31 ASI2016_914 Venkata Suresh Narra Poster

B. Raghavendra Prasad, Indian Institute of Astrophysics Mr. Raj Kumar N, Indian Institute of Astrophysics Jagdev Singh, Indian Institute of Astrophysics Surface roughness requirements on primary mirror of Visible Emission Line Coronagraph (VELC) on board INDIA‟s ADITYA-L1 mission Aditya-L1 is India's first space solar mission to be positioned at first Lagrangian (L1) point. Visible Emission Line Coronagraph (VELC), which is an internally occulted mirror coronagraph, is the primary payload of the mission dedicated for solar coronal studies. VELC is designed for simultaneous narrow band spectroscopic observations in emission lines 7892Å (FeXI), 10747Å (FeXII), 5303Å (FeXIV); spectro-polarimetric observations in emission line 10747Å (FeXII) over a Field Of View (FOV) ±1.05Ro-1.5Ro (Ro-solar Radii); and broad band imaging of solar corona at 5000Å over a FOV ±1.05Ro-3Ro. To achieve the scientific goals of the payload, instrument background should be less than 5ppm (parts per million) over the FOV. The instrument background should follow the profile/trend similar to the coronal intensity variation over the FOV. Major contributor to the instrument background is the scatter due to roughness of primary mirror (M1) surface. Current work is focused on modelling of Bi-Directional Scatter Distribution Function (BSDF) and corresponding scatter distribution over the FOV by simulations in order to arrive at the surface roughness specifications of M1. Estimation of roughness correction factor due to finite band width of the profilometer is very important and it should be taken into account prior to specifying the surface roughness requirements of M1. This paper describes in detail the simulations and results. All the simulations are carried out using Advanced System Analysis Program (ASAP).

IT-32 ASI2016_924 Santaji N Katore Poster

Dharam V. Lal, NCRA Ishwara Chandra, NCRA

Characterising the time-domain band stability of the upgraded GMRT system

Giant Metrewave Radio Telescope (GMRT), located near Pune in India, is an array of radio telescopes at metre wavelengths. It is operated by the National Center for Radio Astrophysics, a part of the Tata Institute of Fundamental Research, Mumbai. GMRT is the world's most sensitive radio interferometer and is currently undergoing a very significant upgrade. One of the key objective of this upgrade is to improve sensitivity. There are several upgrades, e.g., in the front-end RF-receivers, digital backend system, etc. In the new frond-end and the digital back-end upgraded systems, we now have 400 MHz RF receivers, and 400 MHz digital backend. Multiple data sets were collected over more than one year duration as part of regular GMRT upgrade tests. Here we have performed a comparative study between the older GMRT software backend and the newer GMRT wide-band backend over this long time baseline. The cross-correlation amplitude and the relative phase, or the gain variations are used as function of time and frequency-channel for these two systems. Here, we present the improvements in the data quality of the upgraded GMRT system as compared with the old system.

ASI 2016 – Abstract Book 153

IT-33 ASI2016_964 Kumar Poster

T. S. Kumar, A.K. Singh, Lalit Dalakoti and Biman Medhi

Upgradation of the 104 cm ARIES Sampurnanand telescope

In this paper we present the updradation activities being planned for the electrical system of the 104 cm Sampurnanand telescope at ARIES, Nainital. The telescope has f/13 optical system and is supported on off- axis equatorial mount. For pointing both right accession (R.A.) and declination (Dec) axes are provided with four different three phase ac induction motors running at fixed speeds on a UPS power supply. Suitable gear boxes are used with each motor for providing slew, set, fine I and fine II motions ranging from 2 deg/sec to 1 arcsec/sec. A 15 KVA 3 phase UPS is used for operating the entire telescope system including the dome, the instruments and the interfacing PCs. Tracking is achieved using an additional induction motor driven by an inverter which maintains a fixed frequency for providing a constant speed of 15 arcsec/sec. The inverter has two parts: a three phase signal generator and a power amplifier stage. Sidereal time is generated with the help of a 220 v ac, 50 Hz shaded pole induction motor, hour angle (H.A.) and R.A. syncro transmitters and receivers and a differential gearbox. A user operates the telescope using a push button console and the synchro transmitter and receiver dials display R.A., H.A., Dec and sidereal time. The existing electrical system used for controlling the telescope is more than forty years old and most of the components have become obsolete. The drive electronics originally installed for the sidereal clock and tracking motor are based on analogue electronics with components that are no longer available. Since the telescope employs electrical contractor logic and separate motor for each speed the system is quite robust and simple to maintenance. Hence for the upgradation work we combined the robustness of the electrical system and the advantages of the modern microcontroller based systems. The sidereal clock drive has been upgraded with in-house developed microcontroller based single phase digital drive with PWM output. While the tracking drive signal stage has been replaced with a microcontroller based 3 phase signal generator. For RA and Dec slew motions commercially available three phase Siemens drives has been employed and are tuned to provide smooth acceleration and deceleration. Three phase soft starters are used for the set motions and the remaining fine motions are switched directly. A similar contactor logic has been developed for commanding the telescope and for safety interlocking. Here both the RA and Dec functions have been separated in two different electrical panels and can be interfaced with a microcontroller based system. The RA panel has been commissioned successfully while the Dec panel is being developed. Later, the panels will be interfaced with microcontroller system and the telescope would be commanded using a GUI based PC. The drive parameters, the command status, the telescope status and errors could be continuously monitored and logged. A mechanical assembly for coupling the encoders to the main axes is being developed in our workshop. This would help in improving the pointing and tracking accuracies and enable GPS based sidereal time.

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