A sample of Fast Radio Bursts discovered and localised with MeerTRAP at the MeerKAT telescope

TL;DR

This paper reports the discovery and precise localization of three Fast Radio Bursts with MeerTRAP at MeerKAT, analyzes their properties, potential host galaxies, and estimates the all-sky FRB rates, revealing a possible low-fluence deficit.

Contribution

First precise localizations of FRBs with MeerTRAP, including potential host galaxy identification and detailed rate estimates based on a sample of 11 FRBs.

Findings

FRBs localized to ~1 arcmin$^2$ area.

Estimated all-sky FRB rates at 1.28 GHz: ~8.2×10^3 and 2.1×10^3 per day above certain fluences.

Detected a possible low-fluence cutoff in the FRB rate-fluence relation.

Abstract

We present a sample of well-localised Fast Radio Bursts (FRBs) discovered by the MeerTRAP project at the MeerKAT telescope in South Africa. We discovered the three FRBs in single coherent tied-array beams and localised them to an area of ~1 arcmin$^2$. We investigate their burst properties, scattering, repetition rates, and localisations in a multi-wavelength context. FRB 20201211A shows hints of scatter broadening but is otherwise consistent with instrumental dispersion smearing. For FRB 20210202D, we discovered a faint post-cursor burst separated by ~200 ms, suggesting a distinct burst component or a repeat pulse. We attempt to associate the FRBs with host galaxy candidates. For FRB 20210408H, we tentatively (0.35 - 0.53 probability) identify a compatible host at a redshift ~0.5. Additionally, we analyse the MeerTRAP survey properties, such as the survey coverage, fluence completeness, and their implications for the FRB population. Based on the entire sample of 11 MeerTRAP FRBs discovered by the end of 2021, we estimate the FRB all-sky rates and their scaling with the fluence threshold. The inferred FRB all-sky rates at 1.28 GHz are $8.2_{-4.6}^{+8.0}$ and $2.1_{-1.1}^{+1.8} \times 10^3$ sky$^{-1}$ d$^{-1}$ above 0.66 and 3.44 Jy ms for the coherent and incoherent surveys, respectively. The scaling between the MeerTRAP rates is flatter than at higher fluences at the 1.4-$\sigma$ level. There seems to be a deficit of low-fluence FRBs, suggesting a break or turn-over in the rate versus fluence relation below 2 Jy ms. We speculate on cosmological or progenitor-intrinsic origins. The cumulative source counts within our surveys appear consistent with the Euclidean scaling.