Evolutionary Effects in Contact Binaries

Abstract

The structure and evolution of contact binaries is an extremely difficult problem in theoretical astrophysics. Several attempts have been made to set up a satisfactory model, see e.g. Lucy, 1976, Flan-nery, 1976, Shu, Lubow and Anderson, 1976, Robertson and Eggleton, 1977, Rahunen and Vilhu, 1977 and others. There are, roughly, two lines of sight: Shu, Lubow and Anderson postulate the existence of a contact discontinuity in one of the two components of a contact binary (DSC Theory); in this case age zero models in thermal equilibrium are possible. The other authors find that unevolved contact binaries cannot achieve thermal equilibrium; therefore, relaxation oscillations on a thennal time scale are expected (TRO Theory). For a detailed discussion of the different effects see Lucy and Wilson, 1979.

Based on observations obtained at ESO/La Silla