X-ray emission from hydrodynamical simulations in non-LTE wind models

¹ Ústav teoretické fyziky a astrofyziky, Masarykova univerzita, Kotlářská 2, 611 37 Brno, Czech Republic e-mail: krticka@physics.muni.cz
² Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam-Golm, Germany
³ Astronomický ústav, Akademie věd České republiky, 251 65 Ondřejov, Czech Republic

Received: 5 June 2009
Accepted: 9 September 2009

Abstract

Hot stars are sources of X-ray emission originating in their winds. Although hydrodynamical simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on simplifying approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability (seeded by the base perturbation) to derive the analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from observations. Furthermore, the slope of the  relation is in better agreement with observations, however the X-ray luminosity is underestimated by a factor of three. We propose a possible solution for this discrepancy.