NON-LOCAL THERMAL EQUILIBRIUM MODEL ATMOSPHERES FOR THE HOTTEST WHITE DWARFS: SPECTRAL ANALYSIS OF THE COMPACT COMPONENT IN NOVA V4743 Sgr

Journal Article · Thu Jul 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/717/1/363· OSTI ID:21452871

Rauch, T; Werner, K ^[1]; Orio, M ^[2]; Gonzales-Riestra, R ^[3]; Nelson, T ^[4]; Still, M ^[5]; Wilms, J ^[6]

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1. Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, D-72076 Tuebingen (Germany)
2. Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova, vicolo Osservatorio 5, I-35122 Padova (Italy)
3. XMM-Newton Science Operations Centre, European Space Astronomy Centre (ESAC), P.O. Box 78, Villanueva de la Canada, 28691 Madrid (Spain)
4. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
5. NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States)
6. Dr. Remeis-Sternwarte, Astronomical Institute of the University Erlangen-Nuremberg, Sternwartstr. 7, D-96049 Bamberg (Germany)

Half a year after its outburst in 2002 September, nova V4743 Sgr evolved into the brightest supersoft X-ray source in the sky with a flux maximum around 30 A. We calculated grids of synthetic energy distributions based on non-local thermal equilibrium model atmospheres for the analysis of the hottest white dwarfs (WDs) and present the result of fits to Chandra and XMM-Newton grating X-ray spectra of V4743 Sgr of outstanding quality, exhibiting prominent resonance lines of C V, C VI, N VI, N VII, and O VII in absorption. The nova reached its highest effective temperature (T{sub eff} = 740 {+-} 70 kK) around 2003 April and remained at that temperature at least until 2003 September. We conclude that the WD is massive, {approx}1.1-1.2 M{sub sun}. The nuclear-burning phase lasted for 2-2.5 years after the outburst, probably the average duration for a classical nova. The photosphere of V4743 Sgr was strongly carbon deficient ({approx}0.01 times solar) and enriched in nitrogen and oxygen (>5 times solar). Especially the very low C/N ratio indicates that the material at the WD's surface underwent thermonuclear burning. Thus, this nova retained some of the accreted material and did not eject all of it in outburst. From 2003 March to September, the nitrogen abundance is strongly decreasing; new material is probably already being accreted at this stage.

• OSTI ID: 21452871
• Journal Information: Astrophysical Journal, Vol. 717, Issue 1; Other Information: DOI: 10.1088/0004-637X/717/1/363; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ABUNDANCE
COSMIC X-RAY SOURCES
ENERGY SPECTRA
NOVAE
PHOTOSPHERE
THERMAL EQUILIBRIUM
WHITE DWARF STARS
X-RAY SPECTRA
ATMOSPHERES
BINARY STARS
COSMIC RAY SOURCES
DWARF STARS
EQUILIBRIUM
ERUPTIVE VARIABLE STARS
SOLAR ATMOSPHERE
SORPTION
SPECTRA
STARS
STELLAR ATMOSPHERES
VARIABLE STARS