The Sources of Fast Radio Bursts

This paper argues that repeating and apparently non-repeating Fast Radio Bursts are distinct classes of events produced by distinct classes of sources. As for conference proceedings, this paper reviews the evidence for that division, and then discusses the statistics of these classes. They differ in temporal/spectral space, spectral/duration space and rotation measure; the first two differences indicate different emission processes and the last indicates different environments. I discuss two of the many models of each class of source: black hole accretion discs for repeating FRB and hypermagnetized neutron stars (some observed to produce SGR) for apparently non-repeating FRB. Appendices suggest low cutoff frequencies of coherent emission that are consistent with these models and with known pulsars, and discuss the necessary conditions for acceleration of energetic particles.