Binary X-ray sources

The rapid development of X-ray astronomy in recent years, due to the satellites equipped with X-ray telescopes, is briefly discussed. It is shown that most of the known X-ray sources seem to lie in the Milky Way. The role of binary stars as X-ray sources is then discussed, and models for the generation of X-radiation by the 'solar wind' from the normal star being captured by the compact object, or due to the expansion of the normal star outside its Roche lobe, are presented. The binary systems Hercules X-1 and Cygnus X-1 are thereafter discussed in detail. Finally a theory for the origin and development of massive binary X-ray objects, developed by de Loore, de Greve, van de Heuvel and Heise at Utrecht University is presented and discussed. (JIW)