The probable role of cloudy wind structure in the X-ray emission of the binary HD 193793

Abstract

A model with interacting two-phase winds, each consisting of rarified gas and dense, compact clouds, is proposed to explain the weakness of the variability of the X-ray emission of the binary system HD 193793. The flowing together of the rarified components, collisions of clouds, and the motion of the clouds in the rarified component of the other wind are considered. Computations of the interactions of the rarified components were carried out using the method of Cherny$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}$ for standard, two-dimensional, gas-dynamical problems, taking into account differences in the ion and electron temperatures. Due to the adiabatic expansion of the rarifield gas behind the shock front, the X-ray luminosity decreases at 1/r, where r is the distance between the stars in the system. The gas in the dense clouds radiates, leading, on the contrary, to a gradual growth in their luminosity in the transition from periastron to apoastron, approximately proportional to r ^1/3. The joint action of these two factors could give rise to the observed nearly constant luminosity of the system at 2–5 and 2–6 keV. The contribution of the clouds exceeds that of the rarified component by a substantial factor.