LOW MASS X-RAY BINARIES
This is an artist's conception of a low mass X-ray binary star system:
matter from a companion star, most likely a red dwarf, falls slowly onto
a compact object and forms an accretion disk around it.
The compact object can be a neutron star or a black hole.
In both cases, the strong gravitational field accelerates the infalling
matter and forces it to emit high energy photons.
Art Credit: Maggie Masetti, NASA