Evidence For Tev Emission From Grb 970417a

Milagrito, a detector sensitive to gamma -rays at TeV energies, monitored the northern sky during the period February 1997 through Mary 1998. Viiith a large field of view and high duty cycle, this instrument was used to perform a search for TeV counterparts to gamma -ray bursts. BATSE detected 54 GRBs within the field of view of Milagrito during this period. This paper describes the results of an analysis to search for TeV emission correlated with BATSE detected bursts. Milagrito detected an excess of events coincident both spatially and temporally with GRB 970417a, with chance probability 2.8 x 10(-5) within the BATSE error radius. No other significant correlations were detected. Since 54 bursts were examined, the chance probability of observing an excess with at least this significance in any of these bursts is 1.5 x 10(-3).