Early-time Searches for Coherent Radio Emission from Short GRBs with the Murchison Widefield Array

Abstract

Here we present a low frequency (170-200MHz) search for coherent radio emission associated with nine short GRBs detected by the Swift and/or Fermi satellites using the Murchison Widefield Array (MWA) rapid-response observing mode. The MWA began observing these events within 30 to 60s of their high-energy detection, enabling us to capture any dispersion delayed signals emitted by short GRBs for a typical range of redshifts. We conducted transient searches at the GRB positions on timescales of 5s, 30s and 2min, resulting in the most constraining flux density limits on any associated transient of 0.42, 0.29, and 0.084Jy, respectively. We also searched for dispersed signals at a temporal and spectral resolution of 0.5s and 1.28MHz but none were detected. However, the fluence limit of 80-100Jy ms derived for GRB 190627A is the most stringent to date for a short GRB. We compared the fluence and persistent emission limits to short GRB coherent emission models, placing constraints on key parameters including the radio emission efficiency of the nearly merged neutron stars ($\lesssim 10^{-4}$), the fraction of magnetic energy in the GRB jet ($\lesssim 2\times 10^{-4}$), and the radio emission efficiency of the magnetar remnant ($\lesssim 10^{-3}$). Comparing the limits derived for our full GRB sample to the same emission models, we demonstrate that our 30-min flux density limits were sensitive enough to theoretically detect the persistent radio emission from magnetar remnants up to a redshift of $z\sim 0.6$. Our non-detection of this emission could imply that some GRBs in the sample were not genuinely short or did not result from a binary neutron star merger, the GRBs were at high redshifts, these mergers formed atypical magnetars, the radiation beams of the magnetar remnants were pointing away from Earth, or the majority did not form magnetars but rather collapse directly into black holes.

Accepted for publication in PASA

References in corpus (16)

• The NumPy array: a structure for efficient numerical computation
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• A census of baryons in the Universe from localized fast radio bursts
• An optimized algorithm for multi-scale wideband deconvolution of radio astronomical images
• Jet Breaks in Short Gamma-Ray Bursts. II: The Collimated Afterglow of GRB 051221A
• Detailed study of the GRB 030329 radio afterglow deep into the non-relativistic phase
• Pair Fireball Precursors of Neutron Star Mergers
• Hyperaccreting Neutron-Star Disks and Neutrino Annihilation
• A Search for Fast Radio Bursts Associated with Gamma-Ray Bursts
• Limits on GRB Prompt Radio Emission Using the LWA1
• Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars
• LOFAR early-time search for coherent radio emission from Short GRB 181123B
• Constraining a neutron star merger origin for localized fast radio bursts
• LOFAR early-time search for coherent radio emission from GRB 180706A
• Strategies for Finding Prompt Radio Counterparts to Gravitational Wave Transients with the Murchison Widefield Array
• The peculiar physics of GRB 170817A and their implications for short GRBs

Cited by in corpus (9)

• Pulsar revival in neutron star mergers: multi-messenger prospects for the discovery of pre-merger coherent radio emission
• A Stochastic Approach To Reconstruct Gamma Ray Burst Lightcurves
• The most probable host of CHIME FRB 190425A, associated with binary neutron star merger GW190425, and a late-time transient search
• Testing afterglow models of FRB 200428 with early post-burst observations of SGR 1935+2154
• Rapid radio brightening of GRB 210702A
• High time resolution search for prompt radio emission from the long GRB 210419A with the Murchison Widefield Array
• A LOFAR prompt search for radio emission accompanying X-ray flares in GRB 210112A
• A targeted search for repeating fast radio bursts with the MWA
• A Search for Low-frequency Radio Pulses from Long Gamma-ray Bursts with the Murchison Widefield Array