Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NLTE model atmospheres for the hottest white dwarfs: Spectral analysis
  of the compact component in nova V4743 Sgr   Half a year after its outburst in September 2002, nova V4743 Sgr evolved into
the brightest supersoft X-ray source in the sky with a flux maximum around 30A.
We calculated grids of synthetic energy distributions (SEDs) based on NLTE
model atmospheres for the analysis of the hottest white dwarfs 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 +/- 70kK) around April 2003 and remained at that
temperature at least until September 2003. We conclude that the white dwarf is
massive, about 1.1 - 1.2 Msun. The nuclear-burning phase lasted for 2 to 2.5
years after the outburst, probably the average duration for a classical nova.
The photosphere of V4743 Sgr was strongly carbon deficient (about times solar)
and enriched in nitrogen and oxygen (> 5 times solar). Especially the very low
C/N ratio indicates that the material at the white dwarf's surface underwent
thermonuclear burning. Thus, this nova retained some of the accreted material
and did not eject all of it in outburst. From March to September 2003, the
nitrogen abundance is strongly decreasing, probably new material is already
been accreted at this stage.

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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: cond-mat