Constraints on the FRB rate at 700-900 MHz

TL;DR

This paper estimates the all-sky FRB rate at 700-900 MHz based on a single detection, discusses the challenges in rate estimation, and forecasts detection prospects for upcoming low-frequency surveys.

Contribution

It provides the first constraints on the FRB rate at 700-900 MHz and discusses the implications for future low-frequency FRB surveys.

Findings

The estimated FRB rate at 700-900 MHz is consistent with that at 1.4 GHz.

Detection rate forecast for upcoming surveys like CHIME and UTMOST.

Steep flux distributions with gamma > 2.2 are disfavored.

Abstract

Estimating the all-sky rate of fast radio bursts (FRBs) has been difficult due to small-number statistics and the fact that they are seen by disparate surveys in different regions of the sky. In this paper we provide limits for the FRB rate at 800 MHz based on the only burst detected at frequencies below 1.4 GHz, FRB 110523. We discuss the difficulties in rate estimation, particularly in providing an all-sky rate above a single fluence threshold. We find an implied rate between 700-900 MHz that is consistent with the rate at 1.4 GHz, scaling to $6.4^{+29.5}_{-5.0} \times 10^3$\,sky$^{-1}$\,day$^{-1}$ for an HTRU-like survey. This is promising for upcoming experiments below a GHz like CHIME and UTMOST, for which we forecast detection rates. Given 110523's discovery at 32$\sigma$ with nothing weaker detected, down to the threshold of 8$\sigma$, we find consistency with a Euclidean flux distribution but disfavour steep distributions, ruling out $\gamma > 2.2$.