TY - JOUR
T1 - Non-local thermal equilibrium model atmospheres for the hottest white dwarfs
T2 - Spectral analysis of the compact component in nova V4743Sgr
AU - Rauch, T.
AU - Orio, M.
AU - Gonzales-Riestra, R.
AU - Nelson, T.
AU - Still, M.
AU - Werner, K.
AU - Wilms, J.
PY - 2010
Y1 - 2010
N2 - Half a year after its outburst in 2002 September, nova V4743Sgr evolved into the brightest supersoft X-ray source in the sky with a flux maximum around 30 . 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 V4743Sgr 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 ⊙. The nuclear-burning phase lasted for 2-2.5 years after the outburst, probably the average duration for a classical nova. The photosphere of V4743Sgr 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.
AB - Half a year after its outburst in 2002 September, nova V4743Sgr evolved into the brightest supersoft X-ray source in the sky with a flux maximum around 30 . 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 V4743Sgr 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 ⊙. The nuclear-burning phase lasted for 2-2.5 years after the outburst, probably the average duration for a classical nova. The photosphere of V4743Sgr 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.
KW - Cataclysmic variables
KW - Novae
KW - Stars: AGB and post-AGB
KW - Stars: abundances
KW - Stars: atmospheres
KW - Stars: individual (V4743 Sgr)
KW - White dwarfs
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U2 - 10.1088/0004-637X/717/1/363
DO - 10.1088/0004-637X/717/1/363
M3 - Article
AN - SCOPUS:77953741157
SN - 0004-637X
VL - 717
SP - 363
EP - 371
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -