EVOLUTION OF MASSIVE CLOSE BINARIES

An analysis is given of the various aspects of massive close binary evolution, as derived from earlier presented calculations. Apart from the conditions at the beginning and the end of the mass transfer, we specially analyse the evolution covering the core helium burning phase of the primary. For stars with initial mass of the donor M1i greater-than-or-equal-to 20 M. this phase is identified with the WR phase. Finally, the systems at the end of core helium burning are evaluated as possible progenitor systems for the observed massive X ray sources.