Luminosity-duration relations and luminosity functions of repeating and non-repeating fast radio bursts

Abstract

Fast radio bursts (FRBs) are mysterious radio bursts with a time scale of approximately milliseconds. Two populations of FRB, namely repeating and non-repeating FRBs, are observationally identified. However, the differences between these two and their origins are still cloaked in mystery. Here we show the time-integrated luminosity-duration ($L_{\hat{I}}½$-$w_{\mathrm{int},\mathrm{rest}}$) relations and luminosity functions (LFs) of repeating and non-repeating FRBs in the FRB Catalogue project. These two populations are obviously separated in the $L_{\hat{I}}½$-$w_{\mathrm{int},\mathrm{rest}}$ plane with distinct LFs, i.e., repeating FRBs have relatively fainter $L_{\hat{I}}½$ and longer $w_{\mathrm{int},\mathrm{rest}}$ with a much lower LF. In contrast with non-repeating FRBs, repeating FRBs do not show any clear correlation between $L_{\hat{I}}½$ and $w_{\mathrm{int},\mathrm{rest}}$. These results suggest essentially different physical origins of the two. The faint ends of the LFs of repeating and non-repeating FRBs are higher than volumetric occurrence rates of neutron-star mergers and accretion-induced collapse (AIC) of white dwarfs, and are consistent with those of soft gamma-ray repeaters (SGRs), type Ia supernovae, magnetars, and white-dwarf mergers. This indicates two possibilities: either (i) faint non-repeating FRBs originate in neutron-star mergers or AIC and are actually repeating during the lifetime of the progenitor, or (ii) faint non-repeating FRBs originate in any of SGRs, type Ia supernovae, magnetars, and white-dwarf mergers. The bright ends of LFs of repeating and non-repeating FRBs are lower than any candidates of progenitors, suggesting that bright FRBs are produced from a very small fraction of the progenitors regardless of the repetition. Otherwise, they might originate in unknown progenitors.

Accepted by MNRAS. For a summary of the paper, please see below. https://youtu.be/Q0wK6gQzApc