Modelling the energy distribution in CHIME/FRB catalogue-1

We characterize the intrinsic properties of any FRB using its redshift z , spectral index a and energy E 33 in units of 10 33 J emitted across 2128-2848 MHz in the FRB's rest frame. Provided that z is inferred from the measured extra-galactic dispersion measure DMEx, the fluence F of the observed event defines a track in ( a, E 33 ) space which we refer to as the 'energy track'. Here, we consider the energy tracks for a sample of 254 non-repeating low dispersion measure FRBs from the CHIME/FRB catalogue-1, and use these to determine the conditional energy distribution, n(E33|a), i.e. the number of FRBs in the interval AE33 given a value of a. For all values of a, we can identify two distinct energy ranges indicating that there are possibly two distinct FRB populations. At high energies, the distribution is well fitted by a modified Schechter function whose slope and characteristic energy both increase with a. At low energies, the number of FRBs are in excess of the predictions of the modified Schechter function indicating that we may have a distinctly different population of low-energy FRBs. We have checked that our main findings are reasonably robust to the assumptions regarding the Galactic Halo and Host galaxy contributions to the dispersion measure.

Automated summary

We characterized the intrinsic properties of any FRB using redshift z, spectral index a, and energy E33. The energy tracks for a sample of 254 non-repeating low dispersion measure FRBs were considered, and two distinct energy ranges were identified, indicating potentially two distinct FRB populations. High energies followed a modified Schechter function, while low energies exceeded the predictions, suggesting a different population of low-energy FRBs. The main findings were shown to be reasonably robust to assumptions about the Galactic Halo and Host galaxy contributions to the dispersion measure.