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

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 st ar is assumed to possess numerous X-ray emitting "hot" zones that are produ ced by shocks and embedded in the ambient "cold" medium in dynamical equili brium. It is shown that the apparent lack of X-ray variability on short (si milar to hours) timescales do not contradict a shock model for X-ray produc tion. The character of the X-ray variability is found to depend on the freq uency with which hot zones are generated, the cool wind opacity to X-rays, and the wind ow parameters, such as mass loss rate and terminal speed.