Signatures of the Origin of High-Energy Cosmic Rays in Cosmological Gamma-Ray Bursts

Abstract

We derive observational consequences for the hypothesis that cosmic rays (CRs) of energy greater than 1019 eV originate in the same cosmological objects producing gamma-ray bursts (GRBs). Intergalactic magnetic fields 10-12 G are required in this model to allow CRs to be observed continuously in time by producing energy-dependent delays in the CR arrival times. This results in individual CR sources having very narrow observed spectra, since at any given time only those CRs having a fixed time delay are observed. Thus, the brightest CR sources should be different at different energies. The average number of sources contributing to the total CR flux decreases with energy much more rapidly than in a model of steady CR sources, dropping to one at Ecrit 2 × 1020 eV with very weak sensitivity to the intergalactic magnetic field strength. Below Ecrit, a very large number of sources is expected, consistent with observations. Above Ecrit, a source may be observed with a flux considerably higher than the time-averaged CR flux from all sources, if a nearby GRB occurred recently. If such a source is present, its narrow spectrum may produce a gap in the total spectrum. These signatures should be detectable by the planned Auger CR experiment.