A Deep Search for Prompt Radio Emission from the Short GRB 150424A With The Murchison Widefield Array

TL;DR

This study used the Murchison Widefield Array to search for prompt radio signals from short gamma-ray burst 150424A, setting stringent flux limits and exploring implications for models of coherent emission, with future prospects for gravitational wave counterparts.

Contribution

First to set deep flux density limits on prompt radio emission from short GRBs using the MWA, constraining emission models and discussing future gravitational wave searches.

Findings

No excess flux detected in the observations.

Set a 3 sigma flux density limit of 3.0 Jy at 132 MHz.

Discussed potential for constraining models with future gravitational wave detections.

Abstract

We present a search for prompt radio emission associated with the short-duration gamma-ray burst (GRB) 150424A using the Murchison Widefield Array (MWA) at frequencies from 80-133 MHz. Our observations span delays of 23 s-30 min after the GRB, corresponding to dispersion measures of 100-7700 pc/cm^3. We see no excess flux in images with timescales of 4 s, 2 min, or 30 min, and set a 3 sigma flux density limit of 3.0 Jy at 132 MHz on the shortest timescales: some of the most stringent limits to date on prompt radio emission from any type of GRB. We use these limits to constrain a number of proposed models for coherent emission from short-duration GRBs, although we show that our limits are not particularly constraining for fast radio bursts because of reduced sensitivity for this pointing. Finally, we discuss the prospects for using the MWA to search for prompt radio emission from gravitational wave transients and find that while the flux density and luminosity limits are likely to be very constraining, the latency of the gravitational wave alert may limit the robustness of any conclusions.