Fast Radio Bursts: Constraints on the Dispersing Medium

Understand

Fast radio bursts appear to exhibit large dispersion measures, typically exceeding any expected galactic interstellar contribution, especially along the moderate to high-galactic-latitude directions in which such events have been most often observed.

• The dispersions have been therefore interpreted as extragalactic, leading to the inference that the sources of the bursts are at Gpc distances.
• This then implies that the bursts are extremely energetic events, originating from quite small volumes (due to the millisecond burst durations).
• To circumvent the energetic difficulties, Loeb, Shvartzvald, & Maoz (2014) propose that the bursts are produced by flares near the surfaces of M stars or contact binaries within a local volume of the galaxy.