Short-period RS CVn and W UMa binaries: how are they related?

Authors : Frans van`t VEER

Pages : 313-320

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Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Two groups of late-type very close main sequence binaries, the so-called short-period RS Canum Venaticorum insert ignore into journalissuearticles values(RS CVn); and W Ursae Majoris insert ignore into journalissuearticles values(W UMa); systems, are important for the understanding of the structure and evolutionary consequencies of angular momentum loss insert ignore into journalissuearticles values(AML); resulting from magnetic stellar winds of fast rotating solar type stars. The components of RS CVn stars are close to their Roche lobes, but still detached, whereas W UMa binaries are contact systems; both are rotating fast. One of the crucial problems is trying to answer the question if there is a dynamical relation between the two types of binaries in the sense that, as a consequence of the AML, the orbit of the detached sytems will shrink, so that both components come in contact and produce a W UMa type binary. We discuss the relation between wind and starspots and the dependance of AML on the latitude of these spots. No obvious conclusion is possible concerning the shrinking of the orbit of RS CVn binaries. We show that other possibilities for orbits of detached systems with magnetic activity also exist.
Keywords : Turk J Phys, 23, 1999, 313 320 Turk J Phys, vol 23, iss 2