GW170817: implications for the local kilonova rate and for surveys from ground-based facilities

TL;DR

This paper estimates the local rate of kilonova-like events associated with GW170817, compares it with BNS merger rates, and discusses implications for future ground-based and space surveys in detecting such events.

Contribution

It provides the first local rate estimate for GW170817-like kilonova events and analyzes their relation to BNS mergers, informing future survey strategies.

Findings

Estimated local rate of GW170817-like events: ~352 Gpc$^{-3}$yr$^{-1}$

Compared event rate with BNS merger rate, suggesting possible beaming or low fraction of BNSs producing observable sGRBs/KNs

Preliminary predictions for detection rates with upcoming surveys like LSST, ZTF, SKA, and THESEUS.

Abstract

We compute the local rate of events similar to GRB 170817A, which has been recently found to be associated with a kilonova (KN) outburst. Our analysis finds an observed rate of such events of R$_{KN}\sim 352^{+810}_{-281}$ Gpc$^{-3}$yr$^{-1}$. After comparing at their face values this density of sGRB outbursts with the much higher density of Binary Neutron Star (BNS) mergers of 1540$^{+3200}_{-1220}$ Gpc$^{-3}$yr$^{-1}$, estimated by LIGO-Virgo collaboration, one can conclude, admittedly with large uncertainty that either only a minor fraction of BNS mergers produces sGRB/KN events or the sGRBs associated with BNS mergers are beamed and observable under viewing angles as large as $\theta$ $\leq$ $40^{\circ}$. Finally we provide preliminary estimates of the number of sGRB/KN events detected by future surveys carried out with present/future ground-based/space facilities, such as LSST, VST, ZTF, SKA and THESEUS.