Non-LTE Luminosity and Abundance Diagnostics of Classical Novae in X-rays 3 1 0 2 n by a J Peter Nemeth 7 ] R S Master of Science in Astronomy . h p University of Szeged - o Hungary, 2004 r t s a [ 1 v 9 A dissertation submitted to 4 Florida Institute of Technology 2 1 in partial fulfillment of the requirements . 1 0 for the degree of 3 1 : v i X Doctor of Philosophy r a in Physics Melbourne, Florida May 2013 c Copyright 2013 Peter Nemeth (cid:13) All Rights Reserved The author grants permission to make single copies We the undersigned committee hereby recommends that the attached document be accepted as fulfilling in part the requirements for the degree of Doctor of Philosophy in Physics. "Non-LTE Luminosity and Abundance Diagnostics of Classical Novae in X-rays" a dissertation by Peter Nemeth Matthew A. Wood, Ph.D Terry D. Oswalt, Ph.D. Professor Professor, Department Head Dept. of Physics and Space Sciences Dept. of Physics and Space Sciences Academic Advisor Co-Advisor Stephane Vennes, Ph.D. Hamid K. Rassoul, Ph.D. Senior Research Scientist Professor, Associate Dean Astronomický ústav, Ondřejov, Czech Rep. Dept. of Physics and Space Sciences, Guest Member, Former Advisor College of Sciences Committee Member Ming Zhang, Ph.D. Mary L. Sohn, Ph.D. Professor Professor Dept. of Physics and Space Sciences Dept. of Chemistry Committee Member Committee Member ABSTRACT Non-LTE Luminosity and Abundance Diagnostics of Classical Novae in X-rays by Peter Nemeth Academic Advisor: Matthew A. Wood, Ph.D. Classical novae have fundamental importance in astronomy as they are relevant to both an understanding of individual stellar evolution and to taking proper distance measurements on galactic and cosmological scales. Also, novae are significant sources of interstellar material, especially carbon, nitrogen, oxygen and aluminum. These standard candles are only behind supernovae and γ-ray bursts as the third bright- est objects in the sky, and the most probable progenitors of the brightest, type Ia supernovae. Just after a nova outburst the system enters into the constant bolometric luminos- ityphaseandthenovamaintainsastablehydrogenburninginthesurfacelayersofthe white dwarf. As the expanding shell around the nova attenuates, progressively deeper and hotter layers become visible. At the end of the constant bolometric luminosity phase, the hottest layers are exposed and novae radiate X-rays. This work uses the static, plane-parallel model atmosphere code TLUSTY to cal- culate atmospheric structure, and SYNSPEC to calculate synthetic X-ray spectra of iii novae. It was necessary to incorporate atomic data for the highest ionization stages forelementsrangingfromhydrogentoironforbothprograms. Atomicdataonenergy levels, bound-free, bound-bound transitions and natural broadening were taken from NIST and TOPbase. Extensive tests revealed the importance of line opacities on atmospheric parame- ters and on the final spectra. A correlation can be defined between effective temper- ature and surface gravity. The spectral appearance is not very sensitive to the joint changes of both. Due to this effect both parameters might be over-estimated with static models. These tests also showed that N VI and N VII lines are good indicators of effective temperature. Model fitting of V4743 Sgr and V2491 Cyg confirmed the anticipated impact of modeling geometry and stellar wind. Both novae are close to or over the Eddington limit. Ionization balance and line profiles also indicate this. These results are consi- tent with previous studies; further and unambiguous details require a comprehensive update of TLUSTY, what is under way. iv Contents 1 Introduction 1 1.1 The light curve of CNe . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Spectral evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.3 Degeneracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.4 The outburst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.5 Supersoft X-ray Sources . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2 Modeling Hot Atmospheres 23 2.1 Model Atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.2 TLUSTY and SYNSPEC . . . . . . . . . . . . . . . . . . . . . . . . . 29 3 Model Atoms 41 3.1 TOPbase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 3.2 NIST/ASD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3.3 TOPAtom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4 X-ray Modeling of Classical Novae 66 v 4.1 Model Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.2 Trends in the model grid . . . . . . . . . . . . . . . . . . . . . . . . . . 93 4.3 Comparison with TMAP . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5 Observations of Classical Novae 111 5.1 Chandra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 5.2 XMM-Newton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 5.3 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 5.4 Interstellar absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 5.5 Instrumental resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . 121 5.6 Application to Observations . . . . . . . . . . . . . . . . . . . . . . . . 124 5.6.1 V4743 Sgr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.6.2 V2491 Cyg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 6 Conclusions 143 6.1 Future directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Appendices 154 A O VI model atom 155 B Catalog of Galactic CNe with Supersoft Phase 161 vi List of Figures 1.1 General light curve of CNe. . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Temporal spectral evolution of V1974 Cyg.. . . . . . . . . . . . . . . . 6 1.3 Maximum magnitude versus rate of decline (MMRD) curve for CNe. . 7 1.4 Spectral evolution of the FeII class. . . . . . . . . . . . . . . . . . . . . 10 1.5 Spectral evolution of the He/N class. . . . . . . . . . . . . . . . . . . . 12 1.6 Fermi-Dirac distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.7 The mass–radius relationship and mass distribution of WDs . . . . . . 17 1.8 Response of WDs to mass accretion. . . . . . . . . . . . . . . . . . . . 21 2.1 The main steps of model atmosphere calculation. . . . . . . . . . . . . 25 3.1 Example for photoionization cross-sections for Mg. . . . . . . . . . . . 54 3.2 Example for photoionization cross-sections for O. . . . . . . . . . . . . 55 3.3 Grotrian diagram for N VII. . . . . . . . . . . . . . . . . . . . . . . . . 60 3.4 Comparison of Fe VI lines in Kurucz database and TOPbase. . . . . . 63 3.5 349 even parity energy levels for Fe VI in TOPbase and NIST. . . . . 65 4.1 LTE – NLTE comparison. . . . . . . . . . . . . . . . . . . . . . . . . . 68 vii 4.2 Effects of different abundances of carbon on the final spectra. . . . . . 72 4.3 Effects of different abundances of nitrogen on the final spectra. . . . . 73 4.4 Effects of different abundances of neon on the final spectra. . . . . . . 74 4.5 Effects of different abundances of magnesium on the final spectra. . . . 75 4.6 Nova shell abundances. . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.7 Model grid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.8 Final spectrum in LTE and NLTE. . . . . . . . . . . . . . . . . . . . . 81 4.9 Atmospheric structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4.10 Ionization fractions for carbon and nitrogen. . . . . . . . . . . . . . . . 83 4.11 Ionization fractions for oxygen, neon and magnesium. . . . . . . . . . . 84 4.12 Ionization fractions for aluminum, silicon and sulfur. . . . . . . . . . . 85 4.13 Ionization fractions for argon, calcium and iron. . . . . . . . . . . . . . 86 4.14 NLTE departure coefficients of ions from H I – C VI. . . . . . . . . . . 88 4.15 NLTE departure coefficients of ions from N V – N VII. . . . . . . . . . 89 4.16 NLTE departure coefficients of ions from O V – O VIII. . . . . . . . . 90 4.17 Departure coefficients of included ions from Ne VII – Ne X. . . . . . . 91 4.18 Departure coefficients of included ions from Mg IX – Mg XII. . . . . . 92 4.19 NLTE-C convergence log. . . . . . . . . . . . . . . . . . . . . . . . . . 94 4.20 NLTE-L convergence log. . . . . . . . . . . . . . . . . . . . . . . . . . 95 4.21 Gravity sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 4.22 Gravity sequence – structure. . . . . . . . . . . . . . . . . . . . . . . . 97 4.23 PHOENIX flux vs. mass-loss rate. . . . . . . . . . . . . . . . . . . . . 98 viii 4.24 Temperature sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 4.25 Temperature sequence – structure. . . . . . . . . . . . . . . . . . . . . 100 4.26 Temperature–gravity sequence. . . . . . . . . . . . . . . . . . . . . . . 101 4.27 Models close to the Eddington limit. . . . . . . . . . . . . . . . . . . . 103 4.28 Effects of higher energy levels. . . . . . . . . . . . . . . . . . . . . . . . 104 4.29 Effects of metallicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.30 Effects of metallicity on atmospheric structure. . . . . . . . . . . . . . 106 4.31 Thickness of atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . . 107 4.32 Radiation pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 4.33 TMAP models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 4.34 TLUSTY models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 5.1 The Chandra Observatory. . . . . . . . . . . . . . . . . . . . . . . . . . 113 5.2 The structure of HRMA. . . . . . . . . . . . . . . . . . . . . . . . . . . 114 5.3 The XMM-Newton Observatory. . . . . . . . . . . . . . . . . . . . . . 116 5.4 LETG first order effective area for V4743 Sgr. . . . . . . . . . . . . . 118 5.5 Correction for interstellar absorption. . . . . . . . . . . . . . . . . . . . 120 5.6 RGS spectral resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . 122 5.7 Correction for instrumental resolution. . . . . . . . . . . . . . . . . . 123 5.8 Convolution function for instrumental resolution. . . . . . . . . . . . . 123 5.9 Spectral evolution of V4743 Sgr. . . . . . . . . . . . . . . . . . . . . . 126 5.10 Comparison of LETG and RGS spectra. . . . . . . . . . . . . . . . . . 127 5.11 Model fit for V4743 Sgr. March 19, 2003 . . . . . . . . . . . . . . . . . 130 ix