Binary star progenitors of long gamma-ray bursts

Abstract

Context.The collapsar model for long gamma-ray bursts requires a rapidly rotating Wolf-Rayet star as progenitor. Aims.We test the idea of producing rapidly rotating Wolf-Rayet stars in massive close binaries through mass accretion and consecutive quasi-chemically homogeneous evolution - the latter had previously been shown to provide collapsars below a certain metallicity threshold. Conclusions.The binary channel presented here does not, as such, provide a new physical model for collapsar production, as the resulting stellar models are almost identical to quasi-chemically homogeneously evolving rapidly rotating single stars. However, it may provide a means for massive stars to obtain the required high rotation rates. Moreover, it suggests that a possibly large fraction of long gamma-ray bursts occurs in runaway stars.