2004A&A...418L...5D

Gonzalez et al. (2003Natur.424..749G) have reported the discovery of an anomalous radiation component from ≃1-200MeV in GRB 941017. This component varies independently of and contains >3x the energy found in the prompt ∼50keV-1MeV radiation component that is well described by the relativistic synchrotron-shock model. Acceleration of hadrons to very high energies can give rise to two additional emission components, one produced inside the GRB blast wave and one associated with an escaping beam of ultra-high energy (UHE; >10¹⁴eV) neutrons, γ rays, and neutrinos. The first component extending to ∼100MeV is from a pair-photon cascade induced by photomeson processes with the internal synchrotron photons coincident with the prompt radiation. The outflowing UHE neutral beam can undergo further interactions with external photons from the backscattered photon field to produce a beam of hyper-relativistic electrons that lose most of their energy during a fraction of a gyroperiod in the assumed Gauss-strength magnetic fields of the circumburst medium. The synchrotron radiation of these electrons has a spectrum with νF_ν index equal to +1 that can explain the anomalous component in GRB 941017. This interpretation of the spectrum of GRB 941017 requires a high baryon load of the accelerated particles in GRB blast waves. It implies that most of the radiation associated with the anomalous component is released at >500MeV, suitable for observations with GLAST, and with a comparable energy fluence in ∼100TeV neutrinos that could be detected with a km-scale neutrino telescope like IceCube.