Prospects for the detection of GRBs with HAWC

TL;DR

This paper assesses HAWC's potential to detect VHE gamma rays from GRBs, estimating a detection rate of up to 1.65 per year, which could advance understanding of particle acceleration and fundamental physics.

Contribution

It models GRB spectra at very-high energies and predicts HAWC's detection prospects, including the impact of spectral cutoffs and short-hard GRBs.

Findings

HAWC could detect up to 1.65 GRBs per year.

Most sensitivity comes from short-hard GRBs during prompt emission.

Detection rate depends on the intrinsic spectral cutoff energy.

Abstract

The observation of Gamma Ray Bursts (GRBs) with very-high-energy (VHE) gamma rays can provide understanding of the particle acceleration mechanisms in GRBs, and can also be used to probe the extra-galactic background light and place constraints on Lorentz invariance violation. We present prospects for GRB detection by the ground-based HAWC (High Altitude Water Cherenkov) gamma-ray observatory. We model the VHE spectrum of GRBs by extrapolating observations by Fermi LAT and other observatories to higher energies. Under the assumption that only e-pair production associated with extra-galactic background light is responsible for high-energy cutoffs in the spectrum, we find that HAWC will have a detection rate as high as 1.65 GRBs/year. Most of the sensitivity of HAWC to GRBs is derived from short-hard GRBs during the prompt phase. We explore the possibility of universal high-energy cutoffs in GRB spectra and find that the GRB detection rate by HAWC should be at least half of this figure as long as the typical intrinsic cutoff is above 200-300 GeV in the rest frame.