Search for VHE emission from GRB with Milagro

Abstract

The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. Milagro is uniquely capable of searching for very high-energy emission from gamma-ray bursts (GRB) during the prompt emission phase because of its wide field of view and high duty cycle, monitoring the northern sky almost continuously in the 100 GeV to 100 TeV energy range. 33 satellite-triggered GRB have occurred within the field of view of Milagro between January 2000 and December 2003. We have searched for counterparts to these GRB and found no significant emission from any of these burst positions. In the case of GRB 010921, the redshift is low enough (0.45) that our upper limit on the fluence places an observational constraint on potential GRB models. © 2005 American Institute of Physics.