The Mass Spectrum of Black Holes in Close Binary Systems

Abstract

We present the results of population syntheses obtained using our "scenario machine." The mass spectra of black holes in X-ray binary systems before and after the stage of accretion from an optical companion are obtained for various evolutionary scenarios.The results of the model computations are compared to observational data.The observational data are used to estimate the fraction of a pre- supernova's mass that collapses into a black hole.This model can explain the formation of low-mass (2−4 M� ) black holes in binary systems with optical companions.We show that the number of low-mass black holes in the Galaxy is sufficiently high for them to be detected.The population-synthesis results suggest that the vast majority of low-mass black holes are formed via the accretion-induced collapse of neutron stars.The percentage of low-mass black holes in binary systems that form due to accretion- induced collapse is 2-15% of the total number of black holes in binaries, depending on the evolutionary scenario. c � 2005Pleiades Publishing, Inc.