Observational results on compact galactic X-ray sources.

Observational results are discussed concerning the strongest galactic binary X-ray sources. Developments in X-ray astronomy are reviewed, and the following binary sources are treated in detail: Her X-1, Cen X-3, Cyg X-1, and Cyg X-3. Substantial observational data are presented for each source, and it is shown that Her X-1 and Cen X-3 are probably accreting, rotating neutron stars, the Cyg X-1 system contains a black hole, and Cyg X-3 is still unidentified. Other established X-ray binaries are discussed on the basis of their day-to-day and short-term (time scale of 1 sec or less) variabilities.