In effect the compact object "gobbles up" the normal star, and the X-ray emission can provide the best view of how this process occurs.
During outburst, a bright SXT is the brightest object in the X-ray sky, and the apparent magnitude is about 12.
A typical SXT contains a K-type subgiant or dwarf that is transferring mass to a compact object through an accretion disk.
[6][7] Some SXTs in the quiescent state show thermal X-ray radiation from the surface of a neutron star with typical luminosities ~(1032—1034) erg/s.
Analyzing the quiescent thermal states of the SXTs and their crust cooling, one can test the physical properties of the superdense matter in the neutron stars.