Sensitivity of HAWC to Gamma Ray Bursts

摘要

The high-energy spectra of GRBs can provide information on the extragalactic background light, the maximum energy to which GRBs accelerate particles, the Lorentz boost factor of GRB jets, Lorentz invariance violation, etc. HAWC is a ground based detector under construction in M′exico at an altitude of 4100 m, capable of observing GRBs at energies higher than 30 GeV. Two data acquisition (DAQ) systems will operate in HAWC, both of them sensitive to GRBs. The triggered DAQ identifies and reconstructs air showers individually. The scaler DAQ searches for a statistical excess over the average detector-wide PMT background. We show that HAWC is sensitive enough to detect the brightest GRBs detected by Fermi such as GRB 090510 and GRB 090902B. We show that HAWC will be sensitive to energies higher than possible with Fermi. HAWC is a better instrument to observe >30 GeV emission from GRBs than Air Cherenkov Telescopes (ACTs), because it has a very wide field of view ( 2 sr) and near 100% duty cycle. This will allow HAWC to make observations from the beginning of the prompt phase for many GRBs, which is not possible with ACTs. Finally, we discuss the joint interpretation of scalers and triggered event observations and the implications for measuring high-energy spectra of GRBs.