Application of hydrostatic LTE atmosphere models to interpretation of supersoft X-ray sources spectra

Super-soft X-ray sources (SSSs) are accreting white dwarfs (WDs) with stable or recurrent thermonuclear burning on their surfaces. High resolution X-ray spectra of such objects are rather complex, can consist of several components, and are difficult to interpret accurately. The main emission source is the hot surface of the WD, and the emergent radiation can potentially be described by hot WD model atmospheres. We present a new set of such model atmosphere spectra computed in the effective temperature range from 100\,kK to 1000\,kK, for eight values of surface gravity, and three different chemical compositions. These compositions correspond to the solar one and to the Large and Small Magellanic Clouds with decreased heavy element abundances, at one-half and one-tenth of the solar value. The presented model grid covers a broad range of physical parameters, and thus can be applied to a wide range of objects. It is also publicly available in XSPEC format. As an illustration, we applied it here for the interpretation of Chandra and XMM grating spectra of two classical SSSs, namely, CAL$\,83$ (RX$\,$J0543.5$-$6823) and RX$\,$J0513.9$-$6951. The obtained effective temperatures and surface gravities of Teff ≈ 560\,kK, log g ≈ 8.6-8.7, and Teff ≈ 630 kK, log g ≈ 8.5-8.6, respectively, are in a good agreement with previous estimations for both sources. Derived WD~mass estimations are within 1.1-1.4\,M_ for CAL 83 and 1.15-1.4\, M_ for RX$\,$J0513.9$-$6951. The mass of the WD in CAL$\,83$ is consistent with the mass predicted from the respective model of recurrent thermonuclear burning.