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

I. V4743 Sagittarii

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

Abstract

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_eff = 5.8  10⁵ K, with L_bol = 50 000 . The models are calculated for solar abundances. It is shown that the models can be used to determine abundances in the nova ejecta.