ON X-RAY-RADIATION FROM SHOCK-WAVES IN WR+O AND O+O BINARY-SYSTEMS

A comparison has been carried out between the observed X-ray luminosities from shock waves formed by the collision of stellar winds in WR + O and O + O binary systems with close periods and strong difference between mass loss rates M. Despite the fact that the value of M for WR star in WR + O systems. and that for the most luminous O star in O + O systems differ by 1-2 orders of magnitude, X-ray luminosities of the shock waves in such WR + O and O + O systems are close to each other within the limits of the errors of observations. This fact may be considered as an evidence that the physical conditions of the formation of the X-ray radiation in the two classes of binary systems are quite different. The causes for such a difference are analyzed: the enhanced absorption of X-ray radiation in the wind of the WR star, the blob structure of the WR wind, cooling of the hot plasma of the shock wave by inverse Compton scattering as well as cooling of plasma by the radiation in the lines of heavy elements. For the stagnation point of the shock wave, the quantitative estimate of the effect of cooling by inverse Compton scattering and by radiation in lines of heavy elements has been carried out. The conclusion is drawn that investigation of shock waves in WR + O and O + O binary systems is most promising in the hard (E > 10 keV) range.