The HAWC observatory as a GRB detector

TL;DR

The HAWC observatory is designed to detect high-energy gamma-ray bursts, potentially observing components up to 50 GeV, which can shed light on the spectra of GRBs.

Contribution

This paper presents the design and capabilities of HAWC as a new instrument for high-energy GRB detection and reports initial data and limits from a prototype array.

Findings

HAWC can detect high-energy components of GRBs up to 50 GeV.

An engineering array collected 3 months of data, setting upper limits on GRB emissions.

Hawc's observations will inform high-energy spectral models of GRBs.

Abstract

The High Altitude Water Cherenkov Observatory (HAWC) is an air shower array currently under construction in Mexico at an altitude of 4100 m. HAWC will consist of 300 large water tanks covering an area of about 22000 square meters and instrumented with 4 photomultipliers each. The experimental design allows for highly efficient detection of photon-induced air showers in the TeV and sub-TeV range and gamma-hadron separation. We show that HAWC has a reasonable chance to observe the high-energy power law components of GRBs that extend to 50 GeV. In particular, HAWC will be capable of observing events similar to GRB 090510 and GRB 090902B. The observations (or non-observations) of GRBs by HAWC will provide information on the high-energy spectra of GRBs. An engineering array consisting of 6 water tanks was operated at the HAWC site since September 2011, collecting 3 months of data. An upper limit on high energy emission from GRB 111016B is derived from these data.