On Accretion Component of the Flare Activity in Algol

A critical assessment of the observational data on flare activity in Algol-type binaries is given. Two sites of the flare activity have been identified in Algol through observations in the X-ray and microwave regions. One of them is apparently the accretion shock region on the B8-type primary component. Another, the predominant one, is associated with coronal mass ejection from the Roche lobe filling late-type secondary. We still do not know the morphology of the circumbinary gas with sufficient precision to determine the relative contribution from both these sources of activity. Future observations should concentrate both on systems like U Cep with mass-loss dot M =~ 10(-6}M_{sun) /y and on Z Vul-type objects where secondaries are earlier than F2-type stars, i.e. presumably without an extensive convection zone. A simple model of radially expanding stellar wind in a binary system is presented. The effect of anisotropy which appears due to displacement of a sonic point, caused by the gravitational field of the companion star, is investigated. We estimate the X-ray flux for Algol, caused by the accretion to the primary component and find satisfactory agreement with the X-ray Ginga data for a mass transfer rate dot M =(0.4-2.0) * 10(-11}M_{sun) /y.