Using Neutron Stars and Black Holes in X-ray Binaries to Probe Strong Gravitational Fields
Philip Kaaret,
Eric C. Ford
Neutron stars and black holes can be studied by observation of the
radiation produced as matter falls into their gravitational fields.
X-ray binaries, which are systems consisting of a neutron star or black
hole and a companion gaseous star, produce radiation in this manner.
Recently, oscillations at frequencies near 1000 cycles per second have
been detected from x-ray binaries. These oscillations are likely
produced in regions of very strong gravitational fields within a few
tens of kilometers of the compact star. The oscillations have been
interpreted as evidence for the existence of an innermost stable orbit
near a compact star, a key prediction of general relativity theory. The
study of x-ray binaries has also advanced the search for definitive
evidence of black holes. Recent developments in our understanding of
accretion flows in x-ray binaries have provided evidence for the
existence of event horizons in x-ray binaries thought to contain black
holes.
The authors are at the Columbia Astrophysics Laboratory, Columbia
University, New York, NY 10027, USA. E-mail for P. Kaaret:
kaaret{at}astro.columbia.edu
