Double core evolution and X-ray binaries

Abstract

The evolution of a 16-solar mass star and a 1-solar mass neutron star is followed through the common-envelope binary phase. It is found that the encounter of the neutron star with a yellow giant leads to coalescence of the two cores, while encounter with a red giant leads to hydrodynamic expansion and probable ejection of the common envelope. Within the context of the two rotation laws (1) uniform rotation (investigated in the present study), and (2) uniform specific angular momentum (considered in an earlier study), the results are independent of the choice for the angular-momentum distribution in the common envelope. Implications of the results for the binary pulsar phase are discussed.