Proton synchrotron model of TeV gamma ray bursts and their detectability by AMANDA/ICECUBE type detectors

Abstract

The detectability of a possible ``high'' energy (>100 GeV) component of gamma ray bursts (GRBs) using AMANDA/ICECUBE large area muon detectors is examined within the context of a specific model of such high energy gamma ray production within GRBs, namely, the proton-synchrotron model, which requires protons to be accelerated to ultrahigh energies >~1020 eV within GRBs. In this model, the high energy component is distinct from, but may well be emitted in coincidence with, the usual ``low'' (keV-MeV) energy component observed by satellite-borne detectors. The AMANDA/ICECUBE detectors can detect TeV photons by detecting the secondary muons created by the TeV photons in the Earth's atmosphere. We calculate the muon signal-to-noise ratio in these detectors due to TeV gamma rays from individual GRBs for various assumptions on their luminosity, distance (redshift), Lorentz gamma factor of the underlying fireball model, and various spectral characteristics of the GRBs, including the effect of the absorption of TeV photons within the GRB as well as in the intergalactic infrared radiation background. The intergalactic absorption effect essentially precludes detection of TeV photons in the AMANDA detector for reasonable values of the luminosity in the high energy component, but they may well be detectable in the proposed ICECUBE detector which may have an effective area for downward-going muons a factor of 100 larger than that in AMANDA. However, even in ICECUBE, only relatively close-by GRBs at redshifts <0.05 or so can be expected to be detectable with any reasonable degree of confidence. We discuss the requirement on the luminosity of the GRB in the high energy component for its detectability in ICECUBE.