NONCONSERVATIVE MASS TRANSFER IN MASSIVE BINARIES AND THE FORMATION OF WOLF–RAYET+O BINARIES

Abstract

The mass transfer efficiency during the evolution of massive binaries is still uncertain. We model the mass transfer processes in a grid of binaries to investigate the formation of Wolf–Rayet+O (WR+O) binaries, taking into account two kinds of non-conservative mass transfer models: Model I with rotation-dependent mass accretion, and Model II of half mass accretion. Generally the mass transfer in Model I is more inefficient, with the average efficiency in a range of ∼0.2–0.7 and ≲0.2 for Case A and Case B mass transfer, respectively. We present the parameter distributions for the descendant WR+O binaries. By comparing the modeled stellar mass distribution with the observed Galactic WR+O binaries, we find that highly non-conservative mass transfer is required.