Black holes vs neutron stars among SIGMA sources

Abstract

X‐ray binaries form the bulk of hard x‐ray sources, in the 30–300 keV range. More than twenty of them have been detected by SIGMA. Suspected black hole systems seem to be particularly numerous among the sources emitting above 100 keV, and their spectra appear harder than those of neutron star systems. This amounts to a spectral distinction between the two classes of x‐ray binaries. The nature of the companion (high mass or low mass) does not affect this conclusion.