T[CLC]e[/CLC]V Burst of Gamma-Ray Bursts and Ultra–High-Energy Cosmic Rays

Some recent experiments detecting very high energy (VHE) gamma rays above 10-20 TeV independently reported VHE bursts for some bright gamma-ray bursts (GRBs). If these signals are truly from GRBs, these GRBs must emit a much larger amount of energy as VHE gamma rays than in the ordinary photon energy range of GRBs (keV-MeV). We show that such extreme phenomena can be reasonably explained by synchrotron radiation of protons accelerated to ~10 20 -10 21 eV, which we predicted recently. Protons seem to carry about ( m p / m e ) times larger energy than electrons, and hence the total energy liberated by one GRB becomes as large as ~10 56 (ΔΩ/4π) ergs. Therefore, a strong beaming of GRB energy is highly likely. Extension of the VHE spectrum beyond 20 TeV gives a nearly model-independent lower limit of the Lorentz factor of GRBs, as γ≳500. Furthermore, our model gives the correct energy range and time variability of ordinary keV-MeV gamma rays of GRBs by synchrotron radiation of electrons. Therefore, the VHE bursts of GRBs strongly support the hypothesis that ultra-high-energy cosmic rays observed on the Earth are produced by GRBs.