Is there a galactic component for the ultra high energy cosmic rays?

Abstract

Under the hypothesis that Gamma Ray Burst (GRB) might be responsible for the origin of Ultra High Energy Cosmic Ray (UHECR), we propose a two component (galactic and extra-galactic) model for the UHECR origin. The model is based on two facts. The first is the anisotropies found in the angular distribution of GRBs from BATSE catalog. Second is that, of all the located long-GRBs, only approximately 15 percent of them have their spectroscopic redshift determined, and some 38 percent of them have a X-ray, optical, or radio afterglow. So far, in short-GRBs, no afterglow and no red shift have been detected, suggesting that these GRB sources are inside or close to our Galaxy. This two component model for the UHECR is further supported by the experimental evidences of an UHECR excess around $10^{18}$ eV from the direction of the galactic central region. The model offers in a natural way an explanation for the presence of cosmic rays with energies beyond the Greisen-Zatsepin-Kuz'min (GZK) cutoff.