| Type |
Journal Article |
| Names |
T. Rauch, M. Orio, R. Gonzales-Riestra, T. Nelson, M. Still, K. Werner, J. Wilms |
| Publication |
The Astrophysical Journal |
| Volume |
717 |
| Issue |
1 |
| Pages |
363-371 |
| Date |
July 1, 2010 |
| Short Title |
Non-local Thermal Equilibrium Model Atmospheres for the Hottest White Dwarfs |
| URL |
http://adsabs.harvard.edu/abs/2010ApJ...717..363R |
| Library Catalog |
NASA ADS |
| Abstract |
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 Å. 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 (Teff = 740 ± 70 kK) around 2003
April and remained at that temperature at least until 2003 September. We
conclude that the WD is massive, ≈1.1-1.2 M 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 (≈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.
Based on observations collected with XMM-Newton, an ESA Science Mission
with instruments and contributions directly funded by ESA Member States
and the USA (NASA). |
| Tags |
Cataclysmic Variables, NOVAE, STARS: AGB AND POST-AGB, STARS: ATMOSPHERES, Stars: Abundances, stars: individual: V4743 Sgr, white dwarfs |