On astrophysical solution to ultra high energy cosmic rays
Abstract
The energy spectra of Ultra High Energy Cosmic Rays (UHECR) are calculated for several astrophysical models. The attention is given to the accurate calculations of proton energy losses on the microwave radiation. We argue in favor of the astrophysical model valid at energies 1.10^{18} - 8.10^{19} eV with AGN as the sources and UHE protons as the signal carriers. The calculated spectrum has the signatures of interaction with microwave radiation in the form of the dip at E ~ 1.10^{19} eV and of the beginning of the GZK cutoff at (5.3 - 8).10^{19} eV, which seem to be confirmed by the AGASA data. The model meets energy output and acceleration requirements, it explains the small angle clustering and correlation with BL Lacs, though under some extreme assumptions. With this model, the UHECR problem is reduced to a dozen events at energies (1 - 3).10^{20} eV. If confirmed, they have the different origin. We analyze also the problem of the GZK cutoff for UHECR from GRBs and from locally overdensed sources, and found these possibilities disfavored.Keywords
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