Very High Energy Observations of Satellite-Detected Gamma-Ray Bursts

Recent results from the Fermi Gamma-ray Space Telescope indicate that gamma-ray bursts (GRBs) are capable of producing photons with energies up to similar to 90 GeV in the rest frame of the burst. The Fermi-LAT may not be sensitive to the highest energy photons associated with GRBs and ground-based, very high energy (VHE) gamma-ray observatories offer the means by which characterization of GRBs from tens of GeV to TeV energies may be accomplished. Milagro and VERITAS are two such observatories and searches for VHE emission from GRBs have been conducted at both during the past decade. Milagro, an extensive air shower array located near Los Alamos, NM was operational from January, 2000 until May, 2008 and during that time obtained data on nearly 140 satellite-detected GRBs. VERITAS, an imaging atmospheric Cherenkov telescope array has been performing follow-up observations of GRBs since mid 2006 and continues to maintain an active GRB observing program. No significant VHE emission from GRBs has been detected by either experiment. Results from both experiments are presented including those from the Milagro observation of the exceptional "naked-eye" burst GRB 080319B which place stringent constraints on some models of the burst emission, and the VERITAS observation of GRB080310 which began during the prompt phase of the burst which included a large X-ray flare.