The prevalence of repeating fast radio bursts

Abstract

Fast radio bursts are extragalactic, sub-millisecond radio impulses of unknown origin1,2. Their dispersion measures, which quantify the observed frequency-dependent dispersive delays in terms of free-electron column densities, greatly exceed predictions from models3 of the Milky Way interstellar medium. The excess dispersions are probably accrued as fast radio bursts propagate through their host galaxies, gaseous galactic halos and the intergalactic medium4,5. Despite extensive follow-up observations of the published sample of 72 burst sources6, only two have been observed to repeat7,8, and it is unknown whether the remainder are truly one-off events. Here I show that the volumetric occurrence rate of the fast radio bursts that have not been observed to repeat thus far probably exceeds the rates of candidate cataclysmic progenitor events, and also probably 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 (CHIME)9. Within the existing suite of astrophysical scenarios for fast radio burst progenitors, I conclude that most observed cases must originate from sources that emit several bursts over their lifetimes.Of the 72 known fast radio burst (FRB) sources only two have been observed to emit repeat bursts. By calculating the volumetric occurrence rate of non-repeating FRBs, Vikram Ravi shows that there are not enough candidate cataclysmic progenitor events for most FRBs to be one-off phenomena, and therefore most FRBs must repeat.