Introduction
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
X-Ray Flux and Spectral Variability of Blazar H 2356-309
galaxies Article X-ray Flux and Spectral Variability of Blazar H 2356-309 Kiran A. Wani and Haritma Gaur * Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India; [email protected] * Correspondence: [email protected] Received: 6 July 2020; Accepted: 31 July 2020; Published: date Abstract: We present the results of timing and spectral analysis of the blazar H 2356-309 using XMM-Newton observations. This blazar is observed during 13 June 2005–24 December 2013 in total nine observations. Five of the observations show moderate flux variability with amplitude 1.7–2.2%. We search for the intra-day variability timescales in these five light curves, but did not find in any of them. The fractional variability amplitude is generally lower in the soft bands than in the hard bands, which is attributed to the energy dependent synchrotron emission. Using the hardness ratio analysis, we search for the X-ray spectral variability along with flux variability in this source. However, we did not find any significant spectral variability on intra-day timescales. We also investigate the X-ray spectral curvature of blazar H 2356-309 and found that six of our observations are well described by the log parabolic model with α = 1.99–2.15 and β = 0.03–0.18. Three of our observations are well described by power law model. The break energy of the X-ray spectra varies between 1.97–2.31 keV. We investigate the correlation between various parameters that are derived from log parabolic model and their implications are discussed. -
Atmospheric Interpretation of Anomalous Terrestrial
Atmospheric Interpretation of Anomalous Terrestrial Emission Serendipitously Discovered in Radioastronomy Data at 1 Gigahertz Sarah Burke-Spolaor1, Ron Ekers1, and Jean-Pierre Macquart 2 1 CSIRO Astronomy and Space Sciences, PO Box 76, Epping NSW 1710, Australia [email protected] 2 ICRAR/Curtin Institute of Radio Astronomy, GPO Box U1987, Perth WA 6845, Australia Abstract A publication in the Astrophysical Journal [1] reported the discovery of swept-frequency, terrestrial emission in a search for astrophysical pulses. The emission's origin has yet to be determined; its attributes are atypical of known sources of terrestrial signals. We review the observed properties of the emission and present a simple model for a physical mechanism that could occur in the atmosphere to produce it. If this mechanism is the cause of the emission, its origin may lie in secondary effects of lightning production in the upper atmosphere. 1 Introduction Searches for isolated astronomical radio pulses have grown in popularity following a number of recent discoveries [e.g. 2-3]. The surfeit of Earth-origin (man-made and natural) pulses requires these searches to use techniques that discriminate target signals from terrestrial pulses. A basic feature of astronomical pulses is their frequency-dependent delay, which follows δt / f −2. This is an additive dispersion effect resulting from propagation through interstellar plasma that is negligible in locally-generated emission (see Fig. 1). Recently, sixteen terrestrial pulses with frequency-swept characteristics that mimic an astronomical dis- persion delay were reported [1]. They were found in data taken at sparse intervals over the years 1998{2003, using the multibeam receiver on Parkes Radio Telescope in Australia and a specialized back-end hardware that allows 96 spectral bands to be sampled across a 288 MHz bandwidth centered at f = 1:375 GHz. -
Relativistic Jets in Active Galactic Nuclei Und Microquasars
SSRv manuscript No. (will be inserted by the editor) Relativistic Jets in Active Galactic Nuclei and Microquasars Gustavo E. Romero · M. Boettcher · S. Markoff · F. Tavecchio Received: date / Accepted: date Abstract Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly un- derstood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravi- tational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle accelera- tion; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet colli- mation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially Gustavo E. Romero Instituto Argentino de Radioastronoma (IAR), C.C. No. 5, 1894, Buenos Aires, Argentina E-mail: [email protected] M. Boettcher Centre for Space Research, Private Bag X6001, North-West University, Potchef- stroom, 2520, South Africa E-mail: [email protected] S. -
JOHN R. THORSTENSEN Address
CURRICULUM VITAE: JOHN R. THORSTENSEN Address: Department of Physics and Astronomy Dartmouth College 6127 Wilder Laboratory Hanover, NH 03755-3528; (603)-646-2869 [email protected] Undergraduate Studies: Haverford College, B. A. 1974 Astronomy and Physics double major, High Honors in both. Graduate Studies: Ph. D., 1980, University of California, Berkeley Astronomy Department Dissertation : \Optical Studies of Faint Blue X-ray Stars" Graduate Advisor: Professor C. Stuart Bowyer Employment History: Department of Physics and Astronomy, Dartmouth College: { Professor, July 1991 { present { Associate Professor, July 1986 { July 1991 { Assistant Professor, September 1980 { June 1986 Research Assistant, Space Sciences Lab., U.C. Berkeley, 1975 { 1980. Summer Student, National Radio Astronomy Observatory, 1974. Summer Student, Bartol Research Foundation, 1973. Consultant, IBM Corporation, 1973. (STARMAP program). Honors and Awards: Phi Beta Kappa, 1974. National Science Foundation Graduate Fellow, 1974 { 1977. Dorothea Klumpke Roberts Award of the Berkeley Astronomy Dept., 1978. Professional Societies: American Astronomical Society Astronomical Society of the Pacific International Astronomical Union Lifetime Publication List * \Can Collapsed Stars Close the Universe?" Thorstensen, J. R., and Partridge, R. B. 1975, Ap. J., 200, 527. \Optical Identification of Nova Scuti 1975." Raff, M. I., and Thorstensen, J. 1975, P. A. S. P., 87, 593. \Photometry of Slow X-ray Pulsars II: The 13.9 Minute Period of X Persei." Margon, B., Thorstensen, J., Bowyer, S., Mason, K. O., White, N. E., Sanford, P. W., Parkes, G., Stone, R. P. S., and Bailey, J. 1977, Ap. J., 218, 504. \A Spectrophotometric Survey of the A 0535+26 Field." Margon, B., Thorstensen, J., Nelson, J., Chanan, G., and Bowyer, S. -
Naming the Extrasolar Planets
Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named. -
The Midnight Sky: Familiar Notes on the Stars and Planets, Edward Durkin, July 15, 1869 a Good Way to Start – Find North
The expression "dog days" refers to the period from July 3 through Aug. 11 when our brightest night star, SIRIUS (aka the dog star), rises in conjunction* with the sun. Conjunction, in astronomy, is defined as the apparent meeting or passing of two celestial bodies. TAAS Fabulous Fifty A program for those new to astronomy Friday Evening, July 20, 2018, 8:00 pm All TAAS and other new and not so new astronomers are welcome. What is the TAAS Fabulous 50 Program? It is a set of 4 meetings spread across a calendar year in which a beginner to astronomy learns to locate 50 of the most prominent night sky objects visible to the naked eye. These include stars, constellations, asterisms, and Messier objects. Methodology 1. Meeting dates for each season in year 2018 Winter Jan 19 Spring Apr 20 Summer Jul 20 Fall Oct 19 2. Locate the brightest and easiest to observe stars and associated constellations 3. Add new prominent constellations for each season Tonight’s Schedule 8:00 pm – We meet inside for a slide presentation overview of the Summer sky. 8:40 pm – View night sky outside The Midnight Sky: Familiar Notes on the Stars and Planets, Edward Durkin, July 15, 1869 A Good Way to Start – Find North Polaris North Star Polaris is about the 50th brightest star. It appears isolated making it easy to identify. Circumpolar Stars Polaris Horizon Line Albuquerque -- 35° N Circumpolar Stars Capella the Goat Star AS THE WORLD TURNS The Circle of Perpetual Apparition for Albuquerque Deneb 1 URSA MINOR 2 3 2 URSA MAJOR & Vega BIG DIPPER 1 3 Draco 4 Camelopardalis 6 4 Deneb 5 CASSIOPEIA 5 6 Cepheus Capella the Goat Star 2 3 1 Draco Ursa Minor Ursa Major 6 Camelopardalis 4 Cassiopeia 5 Cepheus Clock and Calendar A single map of the stars can show the places of the stars at different hours and months of the year in consequence of the earth’s two primary movements: Daily Clock The rotation of the earth on it's own axis amounts to 360 degrees in 24 hours, or 15 degrees per hour (360/24). -
Cadas Transit October 2014
October Transit 2014 The Newsletter of the Cleveland and Darlington Astronomical Society Page: 1 Header picture: The Sombrero Galaxy (M104) Cover Picture: The Veil Nebula Source: hubblesite.org Taken by: Jurgen Schmoll Next Meeting: Contents: Friday 10th October 7:15pm Editorial Page 2 At Wynyard Planetarium The Decay of the Life in the Sky – 3: Benik Markarian (By Rod Cuff) Page 3 Universe India’s MOM Snaps Spectacular Portrait of New Home Page 6 By Prof. Ruth Gregory Durham University Members Photos Page 8 The Transit Quiz (Neil Haggath) Page 10 Answers to last month’s quiz Page 11 Meetings Calendar Page 12 October Transit 2014 The Newsletter of the Cleveland and Darlington Astronomical Society Page: 2 Editorial Welcome to the October issue of Transit. This month we struggled for articles, but many thanks to Rod Cuff for completing the 3rd in his Life in the Skies series of articles. Thanks also to Jurgen Schmoll, Michael Tiplady and John McCue for their images. We have also reproduced an article from Universe Today (with their kind permission) on the arrival of India’s first interplanetary spacecraft. Any photo’s or articles for next month would be most welcome, but I would also like to ask you the readers what you would like to see in future issues of Transit. Does anyone want to see articles for beginners, or more about practical subjects , finding your way round the night sky, Astronomical History, Current News. Any comments or suggestions would be most welcome. Regards Jon Mathieson Email: [email protected] Phone: +44 7545 641 287 Address: 12 Rushmere, Marton, Middlesbrough, TS8 9XL New Members Dutch astronomer Frans Snik of the European Southern Observatory (ESO) has built his own version of the E-ELT using Lego. -
Pos(NLS1)058 Ce of Broad Emission Lines in Their Ds Reveals Strong Similarities in the Ant Differences (E.G
BL Lac objects with optical jets: PKS 2201+044, 3C 371 and PKS 0521-365. PoS(NLS1)058 E∗. Liuzzo Istituto di Radioastronomia-INAF-Bologna (Italy) E-mail: [email protected] R. Falomo Osservatorio Astronomico di Padova-INAF (Italy) A. Treves Università dell’Insubria (Como-Italy), associated to INAF and INFN We investigate the properties of the three BL Lac objects, PKS 2201+044, 3C 371 and PKS 0521- 365, that exhibit prominent optical jets. We present high resolution near-IR images of the jet of the first two, obtained with an innovative adaptive-optics system (MAD) at ESO VLT telescope. Comparison of the jet in the optical, radio, NIR and X-ray bands reveals strong similarities in the morphology. A common property of these sources is the presence of broad emission lines in their optical spectra at variance with the typical featureless spectrum of the nearby BL Lac objects. Despite some resemblances (e.g. in the radio type), significant differences (e.g. in the central black hole masses and radio structures) with radio-loud NLS1s are found. Narrow-Line Seyfert 1 Galaxies and their place in the Universe - NLS1, April 04-06, 2011 Milan Italy ∗Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/ BL Lac objects with optical jets. E 1. Introduction Radio loud (RL) Active Galactic Nuclei (AGN), in the contrary to their radio quiet (RQ) counterparts, show prominent jets mainly observable in the radio band. Blazars, including BL Lac objects and flat-spectrum radio quasars (FSRQs), are an important class of RL AGNs in which jets are relativistic and beamed in the observing direction. -
X-Ray Flux and Spectral Variability of Blazar H 2356-309
galaxies Article X-ray Flux and Spectral Variability of Blazar H 2356-309 Kiran A. Wani and Haritma Gaur * Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India; [email protected] * Correspondence: [email protected] Received: 6 July 2020; Accepted: 31 July 2020; Published: 10 August 2020 Abstract: We present the results of timing and spectral analysis of the blazar H 2356-309 using XMM-Newton observations. This blazar is observed during 13 June 2005–24 December 2013 in total nine observations. Five of the observations show moderate flux variability with amplitude 1.7–2.2%. We search for the intra-day variability timescales in these five light curves, but did not find in any of them. The fractional variability amplitude is generally lower in the soft bands than in the hard bands, which is attributed to the energy dependent synchrotron emission. Using the hardness ratio analysis, we search for the X-ray spectral variability along with flux variability in this source. However, we did not find any significant spectral variability on intra-day timescales. We also investigate the X-ray spectral curvature of blazar H 2356-309 and found that six of our observations are well described by the log parabolic model with a = 1.99–2.15 and b = 0.03–0.18. Three of our observations are well described by power law model. The break energy of the X-ray spectra varies between 1.97–2.31 keV. We investigate the correlation between various parameters that are derived from log parabolic model and their implications are discussed. -
Optical Counterparts of ROSAT X-Ray Sources in Two Selected Fields at Low
Astronomy & Astrophysics manuscript no. sbg˙comsge˙ed c ESO 2018 October 16, 2018 Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes J. Greiner1, G.A. Richter2 1 Max-Planck-Institut f¨ur extraterrestrische Physik, 85740 Garching, Germany 2 Sternwarte Sonneberg, 96515 Sonneberg, Germany Received 14 October 2013 / Accepted 12 August 2014 ABSTRACT Context. The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. Aims. We investigate two ROSAT All-Sky Survey fields of size 10◦× 10◦ each, one at galactic latitude b = 83◦ (26 Com), the other at b = –5◦ (γ Sge), in order to optically identify the majority of sources. Methods. We used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All- Sky Survey sources. All objects fainter than about 12 mag and brighter than about 17 mag, in or near the error circle of the ROSAT positions, were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol. Results. The present paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analysed. In partic- ular, we found 126 AGN (some of them may be misclassified CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13 mag, 7 UV Cet stars, 3 semiregular resp. slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant and 1 planetary nebula. -
Astronomy 125 Syllabus
Astronomy 125 – Observational Astronomy SEMESTER TIME DAY PLACE FALL 2012 12:00-12:50 p.m. T H Trafton C114 Clear evenings MTWH Standeford Observatory INSTRUCTOR: Dr. James Pierce office: TN N151; phone: 389-1114; office hours: M 12,1,2; T 10,1; W 12,1; H 10,1 email: [email protected]; web: http://mavdisk.mnsu.edu/jpierce/ COURSE MATERIALS: Mechler & Chartrand: National Audubon Society -- Constellations Dickinson et al: Mag 6 Star Atlas Edmund "Star and Planet Locator" Handouts (Download from my website) CONTENT: In this course we will study the night sky and various tools for observing it. We will concentrate on becoming familiar with constellations and bright stars, learning to read star charts, operating small telescopes, and discovering the variety of celestial objects available for observation. Approximate order of lecture topics: celestial sphere; coordinate systems; star charts; sidereal time; telescope optics; telescope specifications; astrophotography; lunar observations; planetary observations. Constellation lectures will be spread throughout the term. See my web page for a more detailed outline. ASSIGNMENTS: Several assignments will be given during the semester to help you become more familiar with the material. Written assignments will be due about a week after they are given out; points will be deducted for late assignments. Observing assignments (which must be done at the observatory) will run throughout the semester observing season. QUIZZES: Five constellation quizzes will be given during the semester; these will check your growing knowledge of the night sky. We will be studying constellations and their components, learning them in groups of six (see the constellation list). -
• Pawan Kumar Outline† Fast Radio Burst Physics & Cosmology
Fast Radio Burst Physics & Cosmology Pawan Kumar Outline† • A brief summary of observations • FRB physics – general constraints & a specific model • FRBs as probe of cosmology †Wenbin Lu, Paz Beniamini (FRB physics) M. Bhattacharya, E. Linder, X. Ma, Eliot Quataert (FRB-cosmology) Paris, May 27, 2021 Fast Radio Bursts (FRBs) * * * * Dispersion relation for EM waves in plasma: # =#+ + - $ ; #+ : plasma frequency "# V = ; signal at # is delayed, wrt # = ∞, by ∝ #)* EM "$ 67489 -3 The magnitude of the delay is ∝ ./ = ∫1234-5 ": ;5 (unit: pc cm ) The first FRB was discovered in 2007 – Parkes 64m radio telescope at 1.4 GHz Lorimer et al. (2007) Lorimer et al. (2007) Duration (δt) = 5ms DM = 375 pc cm-3 (DM from the Galaxy 25 cm-3pc –– high galactic latitude) Estimated distance ~ 500 Mpc (from mean IGM density) ∴ Luminosity = 1043 erg s-1 (1010 times brighter than the Sun) A Brief history (8 years of confusion and then a breakthrough) • 16 more bursts detected (2010) in Parkes archival data by Bailes & Burke-Spolaor These bursts were detected in all 13 beams of the telescope, i.e. most likely terrestrial in origin. Many people suspected that the Lorimer burst was also not cosmological. These bursts were dubbed Peryton – after the mythical winged stag. • Clever detective work by Emily Petroff et al. (2015) established the origin of Perytons (microwave oven!) Arecibo detects a burst in 2012; repeat activity found in 2015 (Spitler et al. 2016). Accurate localization led to distance measurement & confirmation that this event was cosmological and not catastrophic. FRB in our Galaxy! FRB200428 It is associated with a well known magnetar (neutron star with super-strong magnetic field) with 14 B=2.2x10 G; P=3.2s 2 - and spin-down age of 2020) al.