X-ray Binary

Close binary system where a neutron star (or rarely a black hole) accretes matter from what is usually a main sequence star (left). X-ray binaries are some of the most luminous X-ray sources in the sky. X-rays are produced as material from the companion star is drawn to the compact object either through Roche-lobe overflow into an accretion disk (low-mass X-ray binaries) or through direct impact of a stellar wind onto the compact object (high-mass X-ray binaries).

Modified from image source: http://chandra.harvard.edu/photo/2002/xtej1550/.