A Public Set of Synthetic Spectra from Expanding Atmospheres for X-Ray Novae. I. Solar Abundances

TL;DR

This paper introduces a publicly available set of 672 synthetic spectra from expanding atmospheres of X-ray novae with solar abundances, aiding in the interpretation of observed spectra and constraining key physical parameters.

Contribution

It provides a comprehensive grid of wind-type synthetic spectra based on NLTE models, specifically focusing on solar abundances, to improve spectral fitting and parameter estimation for X-ray novae.

Findings

WT spectra fit observed data better than hydro-static models

Key parameters like N_H, L_bol, T_eff, R, v_inf, and M_dot are constrained by spectral fits

Models are sensitive to white dwarf mass but with compensating effects

Abstract

X-ray grating observations have revealed great detail in the spectra of Novae in the Super Soft Source (SSS) phase. Notable features in the SSS spectra are blue-shifted absorption lines, P-Cygni line profiles, and the absence of strong ionization edges, all of which are indicators of an expanding atmosphere. We present, and make publicly available, a set of 672 wind-type (WT) synthetic spectra, obtained from the expanding NLTE SSS models introduced in Van Rossum 2010 with the PHOENIX stellar atmosphere code. The set presented in this paper is limited to solar abundances with the aim to focus on the basic model parameters and their effect on the spectra, providing the basis upon which abundance effects can be studied using a much bigger non-solar set in the next paper in this series. We fit the WT spectra to the five grating spectra taken in the SSS phase of nova V4743 Sgr 2003 as an example application of the WT models. Within the limits of solar abundances we demonstrate that the following parameters are constrained by the data (in order of decreasing accuracy): column density N_H, bolometric luminosity L_bol, effective temperature T_eff, white dwarf radius R, wind asymptotic velocity v_inf, and the mass-loss rate M_dot. The models are also sensitive to the assumed white dwarf mass M_wd but the effect on the spectra can largely be compensated by the other model parameters. The WT spectra with solar abundances fit the data better than abundance optimized hydro-static models.