Les systèmes binaires X.

Observations obtained by Einstein and Exposat are used to study the characteristics, formation, and evolution of X-ray binaries. Results indicate that X-radiation is emitted by these systems when matter is transferred from the normal secondary to the neutron star primary. It is suggested that massive binaries (with companions of spectra type O or B) are detached systems in which mass transfer occurs via a wind, and that weakly massive binaries (with companions of type K or M) are semidetached systems in which mass transfer occurs by overflow of the Roch lobe.