EDP Sciences
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Volume 431, Number 1, February III 2005
Page(s) 321 - 328
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20041396

A&A 431, 321-328 (2005)
DOI: 10.1051/0004-6361:20041396

Modeling CHANDRA low energy transmission grating spectrometer observations of classical novae with PHOENIX

I. V4743 Sagittarii
A. Petz1, P. H. Hauschildt1, J.-U. Ness1 and S. Starrfield2

1  Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: [apetz;yeti;jness]@hs.uni-hamburg.de
2  Department of Physics and Astronomy, Arizona State University, Tempe, AZ 58287-1504, USA
    e-mail: starrfield@asu.edu

(Received 3 June 2004 / Accepted 1 October 2004 )

We use the PHOENIX code package to model the X-ray spectrum of Nova V4743 Sagittarii observed with the LETGS onboard the Chandra satellite 19 March 2003. Our atmosphere models are 1D spherical, expanding, line blanketed, and in full non-local thermodynamic equilibrium. To analyze nova atmospheres and related systems with an underlying nuclear burning envelope at X-ray wavelengths, it was necessary to update the code with new microphysics, as discussed in this paper. We demonstrate that the X-ray emission is dominated by thermal bremsstrahlung and that the hard X-rays are dominated by Fe and N absorption. The best fit to the observation is provided at a temperature of $T_{\rm eff}$ = 5.8  $\times$ 105 K, with $L_{\rm bol}$ = 50 000  $L_\odot$. The models are calculated for solar abundances. It is shown that the models can be used to determine abundances in the nova ejecta.

Key words: stars: novae, cataclysmic variables -- X-rays: individuals: V4743 Sgr -- stars: atmospheres -- atomic data

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© ESO 2005