MWA rapid follow-up of gravitational wave transients: prospects for detecting prompt radio counterparts

TL;DR

This paper evaluates the Murchison Widefield Array's capability to detect prompt radio signals associated with gravitational wave events from neutron star mergers, proposing strategies to optimize detection chances during the LVK O4 run.

Contribution

It introduces a rapid-response observation system for MWA, assesses different configurations for GW follow-up, and predicts detection prospects for coherent radio counterparts.

Findings

Four sub-arrays configuration balances sensitivity and sky coverage.

MWA could detect coherent radio signals from 12.6% of GW BNS events.

Potential detection of 2 coherent emission events during LVK O4.

Abstract

We present and evaluate the prospects for detecting coherent radio counterparts to gravitational wave (GW) events using Murchison Widefield Array (MWA) triggered observations. The MWA rapid-response system, combined with its buffering mode ($\sim4$ minutes negative latency), enables us to catch any radio signals produced from seconds prior to hours after a binary neutron star (BNS) merger. The large field of view of the MWA ($\sim1000\,\text{deg}^2$ at 120\,MHz) and its location under the high sensitivity sky region of the LIGO-Virgo-KAGRA (LVK) detector network, forecast a high chance of being on-target for a GW event. We consider three observing configurations for the MWA to follow up GW BNS merger events, including a single dipole per tile, the full array, and four sub-arrays. We then perform a population synthesis of BNS systems to predict the radio detectable fraction of GW events using these configurations. We find that the configuration with four sub-arrays is the best compromise between sky coverage and sensitivity as it is capable of placing meaningful constraints on the radio emission from 12.6\% of GW BNS detections. Based on the timescales of four BNS merger coherent radio emission models, we propose an observing strategy that involves triggering the buffering mode to target coherent signals emitted prior to, during or shortly following the merger, which is then followed by continued recording for up to three hours to target later time post-merger emission. We expect MWA to trigger on $\sim5\text{--}22$ BNS merger events during the LVK O4 observing run, which could potentially result in two detections of predicted coherent emission.