Observations of gamma-ray bursts at extreme energies

Gamma-ray bursts (GRBs), thought to be produced by the core-collapse of massive stars or merging compact objects, are the most luminous events observed since the Big Bang. GRBs are intrinsically interesting as laboratories to study physical processes at energies much higher than can be produced in the largest particle accelerators on Earth. A better understanding of GRBs may also allow for their use as cosmological tools - backlights for the study of the evolution of the Universe back to the era of the first gravitationally-bound structures. In this work, results from observations of satellite-detected GRBs with the Milagro and VERITAS very high energy (VHE, >100 GeV) gamma-ray telescopes are presented. No significant flux of VHE gamma rays associated with any of the 144 GRBs observed was detected. The limits on VHE gamma-ray emission during the GRB early afterglow phase obtained from the VERITAS observations are among the most constraining to date and the interpretation of these non-detections in the context of GRB emission models is discussed. Results from observation of the "naked-eye burst" GRB 080319B with Milagro are shown to rule out the popular synchrotron self-Compton model of emission over a broad range of energy space. Finally, the prospects for GRB observations with both current and future-generation VHE observatories are examined.