Low-mass X-ray binaries and radiopulsars in binary systems

Abstract

We review the study of high-energy emission from accreting neutron stars and radio pulsars in binary systems with particular emphasis on results from the Compton Observatory. BATSE detected emission in the energy range 20–200 keV from several low-mass X-ray binaries believed to contain weakly magnetized neutron stars. Twelve low-mass X-ray binaries (also including sources detected by SIGMA) have been significantly detected in the hard X-ray band. Before the SIGMA and BATSE discoveries only black hole candidates were known to emit hard X-ray emission. We review the existing observations in the hard X-ray energy band, address the issue of neutron star vs. black hole high-energy emission, and discuss theoretical implications. Binaries containing energetic radiopulsars are also a potential source of high-energy emission. We discuss the important CGRO detection of the Be star/pulsar system PSR B1259−63 near periastron and its implications.