X-ray flash

An X-ray flash (XRF, aka X-ray outburst, XRO) is a short flash of X-rays, much like a gamma-ray burst (GRB). In fact, it is suggested that (at least some) X-ray flashes and gamma-ray bursts stem from the same type of mechanism, i.e., a mechanism producing frequencies in a range spanning the boundary between X-rays and gamma rays. One theory is that the difference between gamma-ray bursts and X-ray flashes is our viewing angle, i.e., that an X-ray flash seen from some directions (that are far away from our view from the solar system) would appear as a GRB, and vice versa.

Note the term X-ray burst is also used, but generally for such transients associated with an X-ray burster, a type of neutron star.