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Issue A&A Volume 373, Number 3, July III 2001 Page(s) 1009 - 1018 Section Stellar atmospheres DOI 10.1051/0004-6361:20010669

A&A 373, 1009-1018 (2001)
DOI: 10.1051/0004-6361:20010669

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

L. M. Oskinova¹, R. Ignace², J. C. Brown¹ and J. P. Cassinelli<sup>3

1</sup>  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

(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.

Key words: stars: abundances -- stars: early-type -- stars: mass-loss -- stars: Wolf-Rayet -- X-rays: stars

Offprint request: L. M. Oskinova, lida@astro.gla.ac.uk

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