The evolution of massive close binaries. V

The final state of the primaries of binary systems with initial masses Msub(1i)=10 solar masses to 15 solar masses is derived from the mass of their C/O-cores. The possibility of a second stage of mass transfer towards the secondary is considered. It turns out that the critical mass for the bifurcation is about 14 solar masses: stars with larger masses in this range are the progenitors of neutron stars, while the lower mass stars are the ancestors of white dwarfs. (Auth.)