The prevalence of repeating fast radio bursts
  Fast radio bursts are extragalactic, sub-millisecond radio impulses of
unknown origin [1,2]. Their dispersion measures, which quantify the observed
frequency-dependent dispersive delays in terms of free-electron column
densities, significantly exceed predictions from models [3] of the Milky Way
interstellar medium. The excess dispersions are likely accrued as fast radio
bursts propagate through their host galaxies, gaseous galactic halos and the
intergalactic medium [4,5]. Despite extensive follow-up observations of the
published sample of 72 burst sources [6], only two are observed to repeat
[7,8], and it is unknown whether or not the remainder are truly one-off events.
Here I show that the volumetric occurrence rate of so far non-repeating fast
radio bursts likely exceeds the rates of candidate cataclysmic progenitor
events, and also likely exceeds the birth rates of candidate compact-object
sources. This analysis is based on the high detection rate of bursts with low
dispersion measures by the Canadian Hydrogen Intensity Mapping Experiment [9].
Within the existing suite of astrophysical scenarios for fast radio burst
progenitors, I conclude that most observed cases originate from sources that
emit several bursts over their lifetimes.
