Early Warnings of Binary Neutron Star Coalescence using the SPIIR Search

TL;DR

This paper evaluates the SPIIR online detection pipeline's ability to provide early warnings of binary neutron star mergers, enabling prompt electromagnetic follow-up within a 10-second window before coalescence.

Contribution

It presents the expected performance of the SPIIR pipeline for early warning detection of neutron star mergers during LIGO-Virgo's O4 run, highlighting its potential for pre-merger alerts.

Findings

Pre-merger warnings possible at least 10 seconds before merger.

Expected alert rate of one per year.

Median sky localization area of 300 square degrees.

Abstract

Gravitational waves from binary neutron star mergers can be used as alerts to enable prompt follow-up observations. In particular, capturing prompt electromagnetic and astroparticle emissions from the moment of a binary merger presents unique constraints on the time scale and sky localization for online gravitational wave detection. Here we present the expected performance of the SPIIR online detection pipeline that is designed for this purpose in the upcoming international LIGO-Virgo's 4th Science Run (O4). Using simulated Gaussian data for the two LIGO observatories with expected O4 sensitivity, we demonstrate that there is a non-negligible opportunity to deliver pre-merger warnings at least 10 s before the final plunge. These alerts are expected to be issued at a nominal rate of one binary neutron star coalescence per year and localized within a median searched area of 300 $deg^2$. We envision such a detection to be extremely useful for follow-up observatories with a large field of view such as the Murchison Widefield Array radio facility at Western Australia.