Milagro—A TeV Observatory for Gamma Ray Bursts

Milagro is a large field of view (∼ 2 sr), high duty cycle (∼90%), ground‐based observatory sensitive to gamma‐rays above ∼100 GeV. This unique detector is ideal for observing the highest energy gamma‐rays from gamma‐ray bursts. The highest energy gamma rays supply very strong constraints on the nature of gamma‐ray burst sources as well as fundamental physics. Because the highest energy gamma‐rays are attenuated by pair production with the extragalactic infrared background light, Milagro’s sensitivity decreases rapidly for bursts with redshift > 0.5. While only 10 % of bursts have been measured to be within z=0.5, these bursts are very well studied at all wavelengths resulting in the most complete understanding of GRB phenomena. Milagro has sufficient sensitivity in units of E2 dN/dE to detect VHE luminosities lower than the observed luminosities at ∼ 100 keV for these nearby bursts. Therefore, the launch of SWIFT and its ability to localize and measure redshifts of many bursts points to great future poss...