Observation of black holes in X-ray binaries

Recent results of X-ray observations of Galactic X-ray binaries containing black holes are reviewed. So far, eleven X-ray binaries are confirmed to contain a black hole based on the mass determined from the optical mass functions. Study of these X-ray binaries shows that accreting black holes exhibit a characteristic X-ray spectrum that is distinct from that of accreting neutron stars. In total, about two dozen X-ray binaries show this characteristic spectrum and are believed to contain a black hole. Most of them are low-mass X-ray binaries and are transients. The statistics indicate the presence of several hundred or more black holes in quiescent X-ray binaries in our galaxy. The observed properties of accreting black holes are discussed, and other, related subjects are also presented.