Black Holes and Neutron Stars: Evolution of Binary Systems

Abstract

The most direct observational evidence for the existence of neutron stars is, of course, the discovery of radio pulsars. A black hole, however, neither radiates electromagnetic energy nor energy in the form of gravitational radiation (Zel’dovich and Novikov, 1967, 1971). Thus, detection of such an object is limited to the influence of its static gravitational field, or to the electromagnetic radiation of gas undergoing accretion or acceleration in its vicinity. Spherically symmetrical accretion by a black hole lying in interstellar matter of typical density leads to a luminosity too small to be of much interest (Zel’dovich and Novikov, 1967, 1971; Schwarzman, 1970). But a black hole member of a binary system presents a more fruitful possibility: the companion star whose electromagnetic radiation is detectable, becomes the object of the black hole’s gravitational influence and is in turn a possible rich source of accretable matter. And, of course, the same possibilities present themselves if one component of the binary is a less-exotic collapsed object — a neutron star or white dwarf. Binary systems containing a white dwarf are ubiquitous; it is a curious fact, however, that not a single radio pulsar seems to be a member of a binary system (Gott et al., 1970).

Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.