Super-eddington accretion onto black holes and ultralurninous X-ray sources

In this review, we discuss the possibility that the soft X-ray transient GRS 1915 + 105 evolved from a binary similar to V4641 Sgr (XTE J1819 - 254) by conservative mass-transfer and estimate the possible mass-transfer rates during the evolution. The results indicate that high mass-transfer rates could explain the high luminosities in ultraluminous X-ray sources. Although the high mass-transfer rates during evolution are accompanied by high luminosities, we find that much of the transferred matter may sweep accompanying radiation in an adiabatic inflow of super-Eddington accretion. We suggest that soft X-ray transients with evolved companions (initial companion mass > 3M(circle dot)) e.g.: GRS 1915 + 105, might be ultraluminous X-ray sources if they are viewed along their beaming axis.