Event Rate of Fast Radio Burst from Binary Neutron-star Mergers

TL;DR

This paper estimates the event rate of fast radio bursts originating from binary neutron-star mergers during inspiral, linking observed FRBs to high-magnetization pre-merger systems and modeling their evolution.

Contribution

It introduces a model connecting FRBs with binary neutron-star mergers and estimates their occurrence rate considering magnetic field decay and population synthesis.

Findings

Event rate of BNS-merger FRBs is approximately 8×10^4 per year at z<1.

High magnetic fields (>10^12 Gs) are necessary for the FRB emission during inspiral.

Most merging BNSs tend to have high magnetization, influencing FRB occurrence.

Abstract

It is proposed that one-off fast radio burst (FRB) with periodic structures may be produced during the inspiral phase of a binary neutron-star (BNS) merger. In this paper, we study the event rate of such kind of FRB. We first investigate the properties of two one-off FRBs with periodic structures (i.e., FRB~20191221A and FRB~20210213A) in this scenario, by assuming the fast magnetosonic wave is responsible for their radio emission. For the luminosities and periods of these bursts, it is found that the pre-merger BNS with magnetic field strength $B\gtrsim 10^{12}\,{\rm Gs}$ is required. This is relatively high compared with that of the most of the BNSs observed in our Galaxy, of which the magnetic field is around $10^{9}\,{\rm Gs}$. Since the observed BNSs in our Galaxy are the binaries without suffering merger, a credited event rate of BNS-merger originated FRBs should be estimated by considering the evolution of both the BNS systems and their magnetic fields. Based on the population synthesis and adopting a decaying magnetic field of NSs, we estimate the event rate of BNS-mergers relative to their final magnetic fields. We find that the rapid merged BNSs tend to merge with high magnetization, and the event rate of BNS-merger originated FRBs, i.e., the BNS-mergers with both NSs' magnetic field being higher than $10^{12}\,{\rm Gs}$ is $\sim8\times10^{4}\,\rm{yr}^{-1}$ ($19 \%$ of the total BNS-mergers) in redshift $z<1$.