The primary known sources of fast radio transients is neutron stars, the dense, massive remnants of supernova explosions. Classes of neutron stars which are observed as fast transients include pulsars (where a pulse of radio emission is observed each time the magnetic pole of the star sweeps past the line-of-sight to the Earth) and RRATs (where a single burst of emission is observed every few minutes or hours - equivalent to once every few thousand rotations of the neutron star).
Other potential sources of fast radio transient emission include the merger of compact objects such as neutron stars or black holes, magnetic flare events in non-degenerate stars, and explosive phenomena such as supernovae or gamma ray bursts. In these cases, the expected properties of the radio emission are uncertain, but the time and size scales are such that transient radio emission is a definite possibility.