Origin and Evolution of X-Ray Binaries and Binary Radio Pulsars

Abstract

a companion star. Optical obser­ vations have shown that there are two main classes of such X-ray binaries: the high-mass X-ray binaries, in which the mass donor is an 0 or B star, and the low-mass X-ray binaries, which have donors less massive than the Sun. It has become clear during the past decade that the neutron star in an X-ray binary may switch on as a radio pulsar when the mass transfer stops. Accordingly, two classes of radio pulsars in binaries can be delin­ eated. Those in which the radio pulsar has another neutron star or a relatively massive (�IM 0) white dwarf as a companion probably have evolved from a high-mass X-ray binary. Those in which the neutron star is accompanied by a low-mass white dwarf (;5 0.5M 0) may have evolved from low-mass X-ray binaries. The origin and evolution of these X-ray binaries and binary radio pulsars are the subject of this review. Origin of high-mass and oflow-mass X-ray binaries and their evolution into binary radio pulsars are discussed in Section 3 and in Section 4. In order not to have to interrupt our discussion of the evolutionary scenarios with the technical explanations of the various processes occurring in them, we start with a separate discussion of these