A Fast Radio Burst (FRB) is a high energy burst of Radio a few milliseconds long. Only a few have been recorded, i.e., 11 as of March 2015, the first one recorded in 2001. The origin is unknown and no other signal has been found to indicate a possible source. Many theories have been put forward (e.g., Neutron Star quakes, Superluminous Supernovae). The antenna that have caught them have isolate them to arcminutes, but their direction needs to be identified in arcseconds to identify a Galaxy or other source. Given current observation counts and the size of the views that yielded observations, it is estimated that the rate across the sky is on the order of 6000 per day.
High pulse Velocity Dispersion has led to suggestions of extra-galactic origin but other theories suggest nearby stars: the Frequency drops roughly linearly, as it would if traveling through the Intergalactic Medium.
Along with the 11 bursts have been some currently discounted bursts, which were labeled Perytons, suspected of being unreal, and later shown to be from opening the door of a nearby Microwave oven. An early claim was that one burst came from M87, but this has been discounted. Bursts have been observed by multiple telescopes, establishing their identity as astronomical. One burst, FRB 121102 has since repeated (non-periodically), yielding a means of studying them in detail and possibly identifying a source.