CHEMICAL EVOLUTION OF ALGOLS

We discuss the chemical abundance peculiarities in Algol-type systems, emphasizing carbon depletion. We consider first some relevant theoret ical aspects of the mass transfer (mass and angular momentum loss, mix ing in the mass-accreting star) and investigate the chemical profile t hroughout the star during core hydrogen burning. The influence of mass transfer during Case B is studied on both the mass and the abundance, as well as the effect of an outer convective zone on carbon abundance . Then we discuss the dimensions of those observed systems for which a carbon abundance of one of the components has been derived, and analy se their evolutionary status in the mass transfer phase from the mass- luminosity position. We give a summary of the results obtained earlier for two particular systems, beta Per and U Sge, and add to that some predictions for the systems S Cnc and TX UMa.