On the sensitivity of the HAWC observatory to gamma-ray bursts

TL;DR

This paper assesses HAWC's potential to detect high-energy gamma-ray bursts, highlighting its design, capabilities, and expected contributions to understanding GRB spectra and related astrophysical phenomena.

Contribution

It presents the sensitivity analysis of HAWC to GRBs, demonstrating its ability to observe high-energy components similar to those detected by Fermi LAT.

Findings

HAWC can observe gamma-ray bursts up to 30 GeV.

Two DAQ systems enable detection of GRB-like events.

HAWC's sensitivity can inform on GRB spectra and cosmic attenuation effects.

Abstract

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles.