X-ray sources in close binary systems: theoretical aspects.

A review is given of the main problems of the theory of disk accretion onto black holes and neutron stars with strong magnetic fields in binary systems. An interpretation is given for the complex variability properties in the sources Cyg X-1, Her X-1. The models of these sources are discussed as well as the nature of transient sources, origin and evolution of bursters and an evolutionary model of the unique γ-ray source Geminga. According to the proposed model, Geminga must be a very bright source of gravitational radiation, 7 - 9 orders of magnitude brighter than all other known sources.