Evolution of Massive Close Binaries

Abstract

An analysis is given of the various aspects of massive close binaryevolution, as derived from earlier presented calculations. Apart fromthe conditions at the beginning and the end of the mass transfer, wespecially analyze the evolution covering the core helium burning phaseof the primary. For stars with initial mass of the donor M1i greaterthan 20 solar masses, this phase is identified with the WR phase.Finally, the systems at the end of core helium burning are evaluated aspossible progenitor systems for the observed massive X-ray sources.