Modelling X-ray variability in the structured atmospheres of hot stars

¹ Department of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, Scotland UK
² Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, USA
³ Department of Astronomy, University of Wisconsin, 5534 Sterling Hall, 475 N. Charter St., Madison, WI 53706-1582, USA

Corresponding author: L. M. Oskinova, lida@astro.gla.ac.uk

Received: 16 February 2001
Accepted: 2 May 2001

Abstract

We describe X-ray production in the atmospheres of hot, early-type stars in the framework of a "stochastic shock model" . The extended envelope of a star is assumed to possess numerous X-ray emitting "hot" zones that are produced by shocks and embedded in the ambient "cold" medium in dynamical equilibrium. It is shown that the apparent lack of X-ray variability on short (~ hours) timescales do not contradict a shock model for X-ray production. The character of the X-ray variability is found to depend on the frequency with which hot zones are generated, the cool wind opacity to X-rays, and the wind flow parameters, such as mass loss rate and terminal speed.