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A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts

S. P. Plunkett·M. Delaney·B. McBreen·K. J. Hurley·C. T. O'Sullivan
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Abstract

A small air shower array operating over many years has been used to search for ultra-high energy (UHE) gamma radiation ($\geq 50$ TeV) associated with gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each burst are presented for seven GRBs located with zenith angles $θ< 20^{\circ}$. A $4.3σ$ excess over background was observed between 10 and 20 minutes following the onset of a GRB on 11 May 1991. The confidence level that this is due to a real effect and not a background fluctuation is 99.8\%. If this effect is real then cosmological models are excluded for this burst because of absorption of UHE gamma rays by the intergalactic radiation fields.

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S. P. Plunkett, M. Delaney, B. McBreen, K. J. Hurley, C. T. O'Sullivan. 1995-08-24. A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts. https://doi.org/10.1007/bf00658630

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