How does X-ray Astronomy Fit In?
X-ray binaries were discovered by rocket flights in the 1960s. These
objects were bright in X-rays but were rather faint optically. More
observations with Uhuru showed them to be pulsating regularly and to show
X-ray eclipses when observed for longer periods. The only explanation was a
close binary system in which a rapidly spinning neutron star was
responsible for the X-rays. Because the binary periods were so fast, it was
recognized that these systems must be so close as to be interacting, with
mass exchanged from the "normal" star to the compact star. As the
matter falls in toward the compact object, it is heated to X-ray
temperatures.
There are two main types of X-ray binaries: Massive X-ray Binaries (MXRBs)
and Low-Mass X-ray Binaries (LMXBs). In MXRBs, material is transferred via
a strong stellar wind from a massive O- or B-type star to the compact
object. In LMXBs, the lower mass stars don't have strong stellar winds.
They require "Roche lobe overflow" to transfer matter to the compact
object. This occurs through the inner Lagrangian point, L1.
Further Binary Resources and References