Measurements of Stellar Magnetic Fields Using Synthetic Spectrum Fitting

Total Page:16

File Type:pdf, Size:1020Kb

Measurements of Stellar Magnetic Fields Using Synthetic Spectrum Fitting Measurements of stellar magnetic fields using synthetic spectrum fitting Nielsen, Krister; Wahlgren, Glenn Published in: Astronomy & Astrophysics DOI: 10.1051/0004-6361:20021276 2002 Link to publication Citation for published version (APA): Nielsen, K., & Wahlgren, G. (2002). Measurements of stellar magnetic fields using synthetic spectrum fitting. Astronomy & Astrophysics, 395(2), 549-556. https://doi.org/10.1051/0004-6361:20021276 Total number of authors: 2 General rights Unless other specific re-use rights are stated the following general rights apply: Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Read more about Creative commons licenses: https://creativecommons.org/licenses/ Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. LUND UNIVERSITY PO Box 117 221 00 Lund +46 46-222 00 00 A&A 395, 549–556 (2002) Astronomy DOI: 10.1051/0004-6361:20021276 & c ESO 2002 Astrophysics Measurements of stellar magnetic fields using synthetic spectrum fitting? K. Nielsen and G. M. Wahlgren Atomic Astrophysics, Lund Observatory, Box 43, 221 00 Lund, Sweden Received 26 June 2002 / Accepted 30 August 2002 Abstract. A sample of Ap and Bp stars have been investigated with respect to their surface magnetic field using synthetic spectrum fitting. The advantage of this technique is the simplicity in determining the surface field strength and the possibility to apply it to objects whose spectrum does not display resolved Zeeman components. We show the usefulness of the method by demonstrations on stellar spectra with resolved Zeeman components, where the results have been compared with values based on measurements of the Zeeman splitting for the magnetically sensitive Fe ii λ6149 line. The objects HD 192678 and HD 165474 have been observed over their rotational period to investigate magnetic field variations. The analysis is then extended to objects where no resolved structure is observed. The rapidly rotating stars HD 22316 and HD 10783 are used as examples where this method is useful to achieve a value of the surface field. The relative intensification of the Fe ii λλ6147, 6149 lines is investigated in an attempt to understand its relation to the surface magnetic field strength for the stars HD 22316 and HD 10783. Key words. magnetic fields – line: profiles – stars: chemically peculiar 1. Introduction structure (Mathys & Lanz 1992; Lanz & Mathys 1993; Hubrig et al. 1999). Stenflo & Lindegren (1977) developed a method Numerous investigations of stellar magnetic fields have been to derive the interdependence of the magnetic field and the performed since Babcock (1947) detected the Zeeman effect in equivalent width based on solar observations, a method later the spectrum of 78 Vir. Most of these studies have measured refined (Mathys & Lanz 1992) to applications in hotter stars the mean longitudinal field (MLF), which is the averaged mag- without resolved Zeeman structure. Takeda (1991) investigated netic field over the stellar surface in the line-of-sight. An anal- the sensitivity of the relative intensification to changes in iron ysis of this kind uses the fact that transitions between magnetic abundance, aspect angle and microturbulence. Unfortunately, sublevels are differently polarized. Therefore, stellar spectra of the method is highly sensitive to line blending and the method opposite circular polarity are used to calculate the Stokes V pa- in converting the equivalent width into a magnetic field strength rameter. is still not fully developed. I Investigations have also made use of the Stokes profile to We present an approach to measure magnetic fields, use- measure the field affecting the atoms in the stellar photosphere ful for spectra without resolved Zeeman structure, built on (Huchra 1972; Preston 1969a,b; Preston & Wolff 1970; Mathys synthetic spectrum fitting. Each spectral line shows a charac- 1990) and uses the Zeeman splitting of magnetically sensitive teristic Zeeman pattern when influenced by a magnetic field spectral lines to measure the surface field, also referred to as and through analysis of the line profile information regarding the mean field modulus (MFM). This method is restricted to the stellar magnetic field can be obtained. To investigate spec- objects with resolved Zeeman components and is not useful for tral line profiles, the observed spectrum is compared with a objects whose spectral lines are predominantly broadened by synthetic spectrum including complete Zeeman patterns. The stellar rotation. method requires calculated Zeeman patterns and knowledge of The equivalent width, Wλ, has been used as a magnetic field the other broadening effects influencing the analyzed spectral indicator for stars with weak field and no observable Zeeman line. The first is simplified by assuming pure LS-coupling and a weak magnetic field to avoid partial Paschen-Back effect, Send offprint requests to: K. Nielsen, e-mail: [email protected] which restricts the investigation to objects with surface fields ? Based on observations obtained with the Nordic Optical less than 7–8 kG. The measured magnetic field is integrated Telescope, operated on the island of La Palma jointly by Denmark, over the stellar surface and is treated as perpendicular to the Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio line-of-sight. Our approach is capable of investigating line pro- del Roque de los Muchachos of the Instituto de Astrofisica de files in the absence of resolved Zeeman components and can be Canarias. used for objects with a weak surface field even if the rotation 550 K. Nielsen and G. M. Wahlgren: Measurements of stellar magnetic fields using synthetic spectrum fitting is the dominating broadening mechanism. Our investigation of Table 2. Observed data. the stellar magnetic field using synthetic spectrum fitting does a not consider the polarization state of the radiation and the influ- Object Sp. type V HJD S=N ence on the radiative transfer by the polarized radiation is not (2 451 700+) included in our synthetic spectrum code. HD 2453 A2p 6.91 74.701 173 HD 10783 A2p 6.55 68.736 180 74.680 223 Table 1. Spectral lines used in the magnetic field analysis. 75.682 193 HD 22316 B9p 6.28 65.738 182 66.607 212 Ion λ (Å) g g log g f b air Jl Ju 67.732 158 Cr ii 6147.154 1.200 1.376 2.843 − HD 165474 A8p 7.50 64.472 193 Fe iia 6147.736 1.200 2.700 2.721 65.480 190 − 6149.248 0 2.700 2.724 66.466 176 − 67.464 175 a Wavelengths from S. Johansson, private communication. 68.493b 83c b Kurucz (1988). 68.519 177 69.413 170 70.413 178 70.499b 139c 2. Observations 71.426 192 72.419 178 All data used in this analysis were obtained with the 2.5 m 73.421 209 Nordic Optical Telescope (NOT) at La Palma, Canary Islands, HD 192678 A4p 7.40 64.437 162 using the SOviet FINish high resolution echelle spectrograph 65.453 169 λ (SOFIN) at a resolving power of R = ∆λ =75 000. The data 66.439 166 set consists of a sequence of observations for each of two 67.437 172 primary targets, HD 192678 and HD 165474 obtained on 10 68.440 114 b c consecutive nights. In addition, single-phase observations of 68.466 105 two stars (HD 2453 and HD 200311) with expected long rota- 69.466 132 67.464b 177c tional periods were made with the purpose of testing the mag- 70.461 139 netic field measurement technique. Two objects, HD 22316 and 71.451 164 HD 10783, do not show resolved Zeeman structure and were 72.444 151 each observed at three phases. The spectral coverage between 73.445 151 5600 7000 Å is not complete and is centered on a spectral re- HD 200311 B9p 7.68 67.490 162 gion− including the magnetically sensitive lines Fe ii λλ6147, a Estimated S=N for the spectral order including Fe ii λλ6147, 6149. 6149 and Cr ii λ6147 (Table 1). Additional observations for b Additional observation for less magnetically sensitive lines. some of the targets were made at shorter wavelengths to cover c Estimated S=N for the spectral order including Fe ii λλ4491, 4508. the less magnetic sensitive lines Fe ii λλ4508, 4491 Å. The complete data set is presented in Table 2. Zeeman components rely on less magnetically sensitive spec- 3. Atmospheric models tral lines, such as Fe ii λλ4491, 4508, with gJ < 0:5 for both The determination of the atmospheric parameters has been the upper and lower level, to place an upper limit on v sin i. accomplished through application of the uvbybeta photo- For the included objects with resolved Zeeman structure v sin i metric calibration program uvbybeta developed by Moon & was estimated using iron lines, especially the less magnetically Dworetsky (1985) and later improved by Napiwotzki et al. sensitive Fe ii λλ4491, 4508 lines, and fine tuned with individ- (1993) based on photometric indices from Hauck & Mermilliod ual Zeeman component of the Fe ii λ6149 line. The rotational (1980). Stellar atmospheric models have been computed using velocity for HD 10783 is based on spectrum fitting using a sam- the LTE approximation with the ATLAS9 code (Kurucz 1993) ple of Fe ii lines in the blue spectral region while for HD 22316 under the assumption of no turbulent velocity.
Recommended publications
  • Rotation Period and Magnetic Field Morphology of the White Dwarf WD
    A&A 439, 1099–1106 (2005) Astronomy DOI: 10.1051/0004-6361:20052642 & c ESO 2005 Astrophysics Rotation period and magnetic field morphology of the white dwarf WD 0009+501 G. Valyavin1,2, S. Bagnulo3, D. Monin4, S. Fabrika2,B.-C.Lee1, G. Galazutdinov1,2,G.A.Wade5, and T. Burlakova2 1 Korea Astronomy and Space Science institute, 61-1, Whaam-Dong, Youseong-Gu, Taejeon 305-348, Republic of Korea e-mail: [email protected] 2 Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Karachai Cherkess Republic 357147, Russia 3 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile 4 Département de Physique et d’Astronomie, Université de Moncton, Moncton, NB, E1A 3E9, Canada 5 Department of Physics, Royal Military College of Canada, PO Box 17000 Stn “FORCES”, Kingston, Ontario, K7K 7B4, Canada Received 5 January 2005 / Accepted 8 May 2005 Abstract. We present new spectropolarimetric observations of the weak-field magnetic white dwarf WD 0009+501. From these data we estimate that the star’s longitudinal magnetic field varies with the rotation phase from about −120 kG to about +50 kG, and that the surface magnetic field varies from about 150 kG to about 300 kG. Earlier estimates of the stellar rotation period are revised anew, and we find that the most probable period is about 8 h. We have attempted to recover the star’s magnetic morphology by modelling the available magnetic observables, assuming that the field is described by the superposition of a dipole and a quadrupole. According to the best-fit model, the inclination of the rotation axis with respect to the line of sight is i = 60◦ ± 20◦, and the angle between the rotation axis and the dipolar axis is β = 111◦ ± 17◦.
    [Show full text]
  • Sun – Part 19 – Magnetic Field 1
    Sun – Part 19 - Magnetic field 1 Solar magnetic field Field line distortion causes sunspots Solar magnetosphere Like all stellar magnetic fields, that of the Sun is generated by the motion of the conductive plasma within it. This motion is created through convection, a form of energy transport involving physical movements of material. Field generation is believed to take place in the Sun's convective zone where the convective circulation of the conducting plasma functions like a dynamo, generating a dipolar stellar magnetic field. In the solar dynamo, the kinetic energy of the hot, highly ionised gas inside the Sun develops self-amplifying electric currents which are converted into the solar magnetic field which gives rise to solar activity. This conversion is due to a combination of differential rotation (different angular velocity of rotation at different latitudes of a gaseous body), Coriolis forces and electrical induction. These rotational effects, and the fact that electrical current distribution can be quite complicated, influence the shape of the Sun's magnetic field, both on large and local scales. In 1952, the American father and son solar astronomers Harold and Horace Babcock developed the solar magnetograph with which they made the first ever measurements of magnetic fields on the Sun's surface. Their work enabled them to develop a model which explains their extensive observations and spectrographic analysis of solar magnetic field behaviour. In this, from large distances, the Sun's magnetic field is a simple dipole, with field lines running between the poles. However, inside the Sun, the rotational effects which help create the field also distort the field lines.
    [Show full text]
  • Origin of Magnetic Fields in Cataclysmic Variables
    Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 16 October 2018 (MN LATEX style file v2.2) Origin of magnetic fields in cataclysmic variables Gordon P. Briggs1, Lilia Ferrario1, Christopher A. Tout1,2,3, Dayal T. Wickramasinghe1 1Mathematical Sciences Institute, The Australian National University, ACT 0200, Australia 2Institute of Astronomy, The Observatories, Madingley Road, Cambridge CB3 0HA 3Monash Centre for Astrophysics, School of Physics and Astronomy, 10 College Walk, Monash University 3800, Australia Accepted. Received ; in original form ABSTRACT In a series of recent papers it has been proposed that high field magnetic white dwarfs are the result of close binary interaction and merging. Population synthesis calculations have shown that the origin of isolated highly magnetic white dwarfs is consistent with the stellar merging hypothesis. In this picture the observed fields are caused by an α−Ω dynamo driven by differential rotation. The strongest fields arise when the differential rotation equals the critical break up velocity and result from the merging of two stars (one of which has a degenerate core) during common envelope evolution or from the merging of two white dwarfs. We now synthesise a population of binary systems to investigate the hypothesis that the magnetic fields in the magnetic cataclysmic variables also originate during stellar interaction in the common envelope phase. Those systems that emerge from common envelope more tightly bound form the cataclysmic variables with the strongest magnetic fields. We vary the common envelope efficiency parameter and compare the results of our population syntheses with observations of magnetic cataclysmic variables. We find that common envelope interaction can explain the observed characteristics of these magnetic systems if the envelope ejection efficiency is low.
    [Show full text]
  • Chandra X-Ray Study Confirms That the Magnetic Standard Ap Star KQ Vel
    A&A 641, L8 (2020) Astronomy https://doi.org/10.1051/0004-6361/202038214 & c ESO 2020 Astrophysics LETTER TO THE EDITOR Chandra X-ray study confirms that the magnetic standard Ap star KQ Vel hosts a neutron star companion? Lidia M. Oskinova1,2, Richard Ignace3, Paolo Leto4, and Konstantin A. Postnov5,2 1 Institute for Physics and Astronomy, University Potsdam, 14476 Potsdam, Germany e-mail: [email protected] 2 Department of Astronomy, Kazan Federal University, Kremlevskaya Str 18, Kazan, Russia 3 Department of Physics & Astronomy, East Tennessee State University, Johnson City, TN 37614, USA 4 NAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy 5 Sternberg Astronomical Institute, M.V. Lomonosov Moscow University, Universitetskij pr. 13, 119234 Moscow, Russia Received 20 April 2020 / Accepted 20 July 2020 ABSTRACT Context. KQ Vel is a peculiar A0p star with a strong surface magnetic field of about 7.5 kG. It has a slow rotational period of nearly 8 years. Bailey et al. (A&A, 575, A115) detected a binary companion of uncertain nature and suggested that it might be a neutron star or a black hole. Aims. We analyze X-ray data obtained by the Chandra telescope to ascertain information about the stellar magnetic field and/or interaction between the star and its companion. Methods. We confirm previous X-ray detections of KQ Vel with a relatively high X-ray luminosity of 2 × 1030 erg s−1. The X-ray spectra suggest the presence of hot gas at >20 MK and, possibly, of a nonthermal component.
    [Show full text]
  • Arxiv:1709.05344V1 [Astro-Ph.SR] 15 Sep 2017 (A(Li) = 2.75), Higher Than Its Companion by 0.5 Dex
    Draft version September 19, 2017 Typeset using LATEX modern style in AASTeX61 KRONOS & KRIOS: EVIDENCE FOR ACCRETION OF A MASSIVE, ROCKY PLANETARY SYSTEM IN A COMOVING PAIR OF SOLAR-TYPE STARS Semyeong Oh,1, 2 Adrian M. Price-Whelan,1 John M. Brewer,3, 4 David W. Hogg,5, 6, 7, 8 David N. Spergel,1, 5 and Justin Myles3 1Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA 2To whom correspondence should be addressed: [email protected] 3Department of Astronomy, Yale University, 260 Whitney Ave, New Haven, CT 06511, USA 4Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA 5Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave, New York, NY 10010, USA 6Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA 7Center for Data Science, New York University, 60 Fifth Ave, New York, NY 10011, USA 8Max-Planck-Institut f¨ur Astronomie, K¨onigstuhl17, D-69117 Heidelberg ABSTRACT We report and discuss the discovery of a comoving pair of bright solar-type stars, HD 240430 and HD 240429, with a significant difference in their chemical abundances. The two stars have an estimated 3D separation of ≈ 0:6 pc (≈ 0:01 pc projected) at a distance of r ≈ 100 pc with nearly identical three-dimensional velocities, as inferred from Gaia TGAS parallaxes and proper motions, and high-precision radial velocity measurements. Stellar parameters determined from high-resolution Keck HIRES spectra indicate that both stars are ∼ 4 Gyr old. The more metal-rich of the two, HD 240430, shows an enhancement of refractory (TC > 1200 K) elements by ≈ 0:2 dex and a marginal enhancement of (moderately) volatile elements (TC < 1200 K; C, N, O, Na, and Mn).
    [Show full text]
  • On the Variation of the Microturbulence Parameter with Chemical Composition
    1 . ON THE VARIATION OF THE MICROTURBULENCE PARAMETER WITH CHEMICAL COMPOSITION S. E. Strom $- $- CSFTI PRICE(S) $ Micrcfiche (MF) I b.5' ff 653 Julb 65 January 1968 Smithsonian Institution Ast r ophys ica1 Ob s e rvato r y Cambridge, Massachusetts 021 38 I ON THE VARIATION OF THE MICROTURBULENCE PARAMETER WITH CHEMICAL COMPOSITION S. E. STROM Smithsonian Astrophysical Observatory Cambridge, Massachusetts Received ABSTRACT It is shown that the correlation found bv previous investigators between and the iron to hydrogen .-t .-t the value of the microturbulent velocity parameter 5 ratio for G dwarfs results from invalid assumptions implicit in the differen- tial curve-of-growth techniques used to derive By using model atmos- 6 t' phere abundance analyses, the deduced values of EL will be very close to the ~. mean value found for stars for approximately solar composition. Several authors (e. g., Wallerstein 1962, Aller and Greenstein 1960) have suggested on the basis of differential curve-of -growth (DCOG) analyses that extreme subdwarf atmospheres are characterized by unusually small values of the turbulent velocity parameter Wallerstein (1962) has presented 5 t' evidence that the turbulent velocity decreases along with the iron-to-hydrogen ratio and thus, in a crude way, with age. This suggestion has led to the speculation that the lower values of et (e, 5 1 km/sec) for the most metal- deficient subdwarfs are related to the decrease of chromospheric activity with age. Recent work by Cohen and Strom (1968), based on detailed model atmospheres, contradicts the results of previous investigations in that for two extreme subdwarfs, HD 19445 and HD 140283, they find, respectively, & - 2 km/sec and 2 5,L 3 km/sec.
    [Show full text]
  • Chlorine Isotope Ratios in M Giants
    Draft version August 4, 2021 Typeset using LATEX twocolumn style in AASTeX62 Chlorine Isotope Ratios in M Giants Z. G. Maas1 and C. A. Pilachowski1 1Indiana University Bloomington, Astronomy Department, 727 East Third Street, Bloomington, IN 47405, USA ABSTRACT We have measured the chlorine isotope ratio in six M giant stars using HCl 1-0 P8 features at 3.7 microns with R ∼ 50,000 spectra from Phoenix on Gemini South. The average Cl isotope ratio for our sample of stars is 2.66 ± 0.58 and the range of measured Cl isotope ratios is 1.76 < 35Cl/37Cl < 3.42. The solar system meteoric Cl isotope ratio of 3.13 is consistent with the range seen in the six stars. We suspect the large variations in Cl isotope ratio are intrinsic to the stars in our sample given the uncertainties. Our average isotopic ratio is higher than the value of 1.80 for the solar neighborhood at solar metallicity predicted by galactic chemical evolution models. Finally the stellar isotope ratios in our sample are similar to those measured in the interstellar medium. Keywords: stars: abundances; 1. INTRODUCTION solar system 37Cl abundance (Pignatari et al. 2010). 37 The odd, light elements are useful for understanding Cl production via the s-process in AGB stars is not the production sites of secondary nucleosynthesis pro- thought to be as significant as from the weak s-process cesses. However, some of the odd light elements, such (Cristallo et al. 2015; Karakas & Lugaro 2016). For ex- as P, Cl, and K have few measured stellar abundances ample, FRUITY models predict only a ∼ 3% increase 37 and/or do not match predicted chemical evolution mod- in Cl for a 4 M solar metallicity AGB star and a els (see Nomoto et al.
    [Show full text]
  • Radio Emission from Exoplanets: the Role of the Stellar Coronal Density and Magnetic Field Strength
    A&A 490, 843–851 (2008) Astronomy DOI: 10.1051/0004-6361:20078658 & c ESO 2008 Astrophysics Radio emission from exoplanets: the role of the stellar coronal density and magnetic field strength M. Jardine and A. C. Cameron SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Scotland KY16 9SS, UK e-mail: [email protected] Received 12 September 2007 / Accepted 5 August 2008 ABSTRACT Context. The search for radio emission from extra-solar planets has so far been unsuccessful. Much of the effort in modelling the predicted emission has been based on the analogy with the well-known emission from Jupiter. Unlike Jupiter, however, many of the targets of these radio searches are so close to their parent stars that they may well lie inside the stellar magnetosphere. Aims. For these close-in planets we determine which physical processes dominate the radio emission and compare our results to those for large-orbit planets that are that are immersed in the stellar wind. Methods. We have modelled the reconnection of the stellar and planetary magnetic fields. We calculate the extent of the planetary magnetosphere if it is in pressure balance with its surroundings and determine the conditions under which reconnection of the stellar and planetary magnetic fields could provide the accelerated electrons necessary for the predicted radio emission. Results. We show that received radio fluxes of tens of mJy are possible for exoplanets in the solar neighbourhood that are close to their parent stars if their stars have surface field strengths above 1–10 G.
    [Show full text]
  • Testing the Fossil Field Hypothesis: Could Strongly Magnetised OB Stars Produce All Known Magnetars?
    MNRAS 000,1–17 (2020) Preprint 22 April 2021 Compiled using MNRAS LATEX style file v3.0 Testing the fossil field hypothesis: could strongly magnetised OB stars produce all known magnetars? Ekaterina I. Makarenko 1¢ Andrei P. Igoshev,2 A.F. Kholtygin3,4 1I.Physikalisches Institut, Universität zu Köln, Zülpicher Str.77, Köln D-50937, Germany 2Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT , UK 3Saint Petersburg State University, Saint Petersburg, 199034, Russia 4Institute of Astronomy, Russian Academy of Sciences, Moscow 119017, Russia Accepted XXX. Received YYY; in original form ZZZ ABSTRACT Stars of spectral types O and B produce neutron stars (NSs) after supernova explosions. Most of NSs are strongly magnetised including normal radio pulsars with 퐵 / 1012 G and magnetars with 퐵 / 1014 G. A fraction of 7-12 per cent of massive stars are also magnetised with 퐵 / 103 G and some are weakly magnetised with 퐵 / 1 G. It was suggested that magnetic fields of NSs could be the fossil remnants of magnetic fields of their progenitors. This work is dedicated to study this hypothesis. First, we gather all modern precise measurements of surface magnetic fields in O, B and A stars. Second, we estimate parameters for log-normal distribution of magnetic fields in B stars and found `퐵 = 2.83±0.1 log10 (G), f퐵 = 0.65±0.09 ± 0.57 for strongly magnetised and `퐵 = 0.14 0.5 log10 (G), f = 0.7−0.27 for weakly magnetised. Third, we assume that the magnetic field of pulsars and magnetars have 2.7 DEX difference in magnetic fields and magnetars represent 10 per cent of all young NSs and run population synthesis.
    [Show full text]
  • A COMPREHENSIVE STUDY of SUPERNOVAE MODELING By
    A COMPREHENSIVE STUDY OF SUPERNOVAE MODELING by Chengdong Li BS, University of Science and Technology of China, 2006 MS, University of Pittsburgh, 2007 Submitted to the Graduate Faculty of the Dietrich School of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2013 UNIVERSITY OF PITTSBURGH PHYSICS AND ASTRONOMY DEPARTMENT This dissertation was presented by Chengdong Li It was defended on January 22nd 2013 and approved by John Hillier, Professor, Department of Physics and Astronomy Rupert Croft, Associate Professor, Department of Physics Steven Dytman, Professor, Department of Physics and Astronomy Michael Wood-Vasey, Assistant Professor, Department of Physics and Astronomy Andrew Zentner, Associate Professor, Department of Physics and Astronomy Dissertation Director: John Hillier, Professor, Department of Physics and Astronomy ii Copyright ⃝c by Chengdong Li 2013 iii A COMPREHENSIVE STUDY OF SUPERNOVAE MODELING Chengdong Li, PhD University of Pittsburgh, 2013 The evolution of massive stars, as well as their endpoints as supernovae (SNe), is important both in astrophysics and cosmology. While tremendous progress towards an understanding of SNe has been made, there are still many unanswered questions. The goal of this thesis is to study the evolution of massive stars, both before and after explosion. In the case of SNe, we synthesize supernova light curves and spectra by relaxing two assumptions made in previous investigations with the the radiative transfer code cmfgen, and explore the effects of these two assumptions. Previous studies with cmfgen assumed γ-rays from radioactive decay deposit all energy into heating. However, some of the energy excites and ionizes the medium.
    [Show full text]
  • Radio and High-Energy Emission of Pulsars Revealed by General Relativity Q
    A&A 639, A75 (2020) Astronomy https://doi.org/10.1051/0004-6361/202037979 & c Q. Giraud and J. Pétri 2020 Astrophysics Radio and high-energy emission of pulsars revealed by general relativity Q. Giraud and J. Pétri Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France e-mail: [email protected] Received 18 March 2020 / Accepted 14 May 2020 ABSTRACT Context. According to current pulsar emission models, photons are produced within their magnetosphere and current sheet, along their separatrix, which is located inside and outside the light cylinder. Radio emission is favoured in the vicinity of the polar caps, whereas the high-energy counterpart is presumably enhanced in regions around the light cylinder, whether this is the magnetosphere and/or the wind. However, the gravitational effect on their light curves and spectral properties has only been sparsely researched. Aims. We present a method for simulating the influence that the gravitational field of the neutron star has on its emission properties according to the solution of a rotating dipole evolving in a slowly rotating neutron star metric described by general relativity. Methods. We numerically computed photon trajectories assuming a background Schwarzschild metric, applying our method to neu- tron star radiation mechanisms such as thermal emission from hot spots and non-thermal magnetospheric emission by curvature radiation. We detail the general-relativistic effects onto observations made by a distant observer. Results. Sky maps are computed using the vacuum electromagnetic field of a general-relativistic rotating dipole, extending previous works obtained for the Deutsch solution. We compare Newtonian results to their general-relativistic counterpart.
    [Show full text]
  • Arxiv:2002.08727V1 [Astro-Ph.EP] 20 Feb 2020
    Draft version June 15, 2020 Typeset using LATEX preprint style in AASTeX63 Coherent radio emission from a quiescent red dwarf indicative of star-planet interaction H. K. Vedantham,1, 2 J. R. Callingham,1 T. W. Shimwell,1, 3 C. Tasse,4 B. J. S. Pope,5 M. Bedell,6 I. Snellen,3 P. Best,7 M. J. Hardcastle,8 M. Haverkorn,9 A. Mechev,3 S. P. O'Sullivan,10, 11 H. J. A. Rottgering,¨ 3 and G. J. White12, 13 1ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, Dwingeloo, 7991 PD, The Netherlands 2Kapteyn Astronomical Institute, University of Groningen, PO Box 72, 97200 AB, Groningen, The Netherlands 3Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands 4GEPI, Observatoire de Paris, Universit´ePSL, CNRS, 5 place Jules Janssen, 92190 Meudon, France 5NASA Sagan Fellow, Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA 6Flatiron Institute, Simons Foundation, 162 Fifth Ave, New York, NY 10010, USA 7Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ 8Centre for Astrophysics Research, University of Hertford-shire, College Lane, Hatfield AL10 9AB 9Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, Netherlands 10Hamburger Sternwarte, Universit¨atHamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany 11School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University, Glasnevin, D09 W6Y4, Ireland 12Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK 13RAL Space, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK ABSTRACT Low frequency (ν .
    [Show full text]