Numerical simulation of the gas flow in close binary systems.

Abstract

A hydrodynamical calculation of the gas flow in a semidetached close binary system is presented. The steady- state solutions for three separate cases are considered, viz., synchronous rotation of both components, non- synchronous rotation of the secondary (less massive) component, and nonsynchronous rotation of the primary (more massive) component. In all cases a shock (hot spot) forms on the surface of the primary. In addition, a turbulent region probably forms from a shock resulting from the collision of the returning stream (the stream that completes a full orbit around the primary) with the main stream between the components. Nonsynchronous rotation of the secondary leads to a ring around the primary, with the gas flowing along nearly circular streamlines. Also, a density protuberance is seen in the vicinity of the advancing hemisphere of the primary component. In contrast, a detachment of the stream from the surface of the primary in the same vicinity of the advancing hemisphere of the primary results in the other two cases. In addition, the streamlines in this region are more elliptical in shape. Finally, a theoretical velocity curve is constructed, and an attempt is made to compare it with an observational velocity curve. Subject headings: binaries - hydrodynamics