Possible Association of Ultra–High-Energy Cosmic-Ray Events with Strong Gamma-Ray Bursts

We point out that each of the error boxes of the two highest-energycosmic-ray shower events known, overlaps with that of a strong gamma-ray burst(GRB). The GRBs precede the cosmic rays by 5.5, and 11 months respectively. Inone case the strongest known cosmic ray is paired with the strongest gamma-rayburst in the BATSE catalogue. The probability of this to have occurred bychance seems rather small. Without building on post-factum statistics, we thinkthe above is remarkable enough to suggest that the cosmic ray and gamma-rayburst were produced by the same outburst. A time delay (and a small positionaldisparity) is expected, since the trajectory of a charged cosmic-ray particleis wriggled by intervening magnetic fields. We estimate that the Galaxy's fieldalone may produce a delay of the order observed. We discuss some of theimplications that follow if such an association is confirmed. For example, theupper limit on the distance to the cosmic-ray source, combined with amuch-better-determined position of the gamma-ray burst source, narrows greatlythe volume in which to look for an optical counterpart. There is also usefulinformation in the time delay regarding, e.g., intergalactic magnetic fields.Comment: 9 pages, Latex, requires aaspp.sty, attached at the end. Submitted to Ap J Let