TP-21

Black Holes in Soft X-Ray Transients and Collapsars

G.E. Brown, Chang-Hwan Lee, H.A. Bethe

We suggest that high-mass black holes; i.e., black holes of several solar masses, can be formed in binaries with low-mass main-sequence companions, provided that the hydrogen envelope of the massive star is removed in common envelope evolution which begins only after the massive star has finished He core burning. Our evolution scenario naturally explains the observed mass gaps (low probability region in mass) in high mass black holes. A possible connection between high-mass black holes in soft X-ray transients and collapsars is discussed.