TeV gamma-ray emission from gamma-ray bursts and ultra high energy cosmic rays.
Abstract (from CDS):
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), although further confirmation is necessary. 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 ∼1020–21eV. Protons must carry a much larger amount of energy than electrons, suggesting that energy transfer from protons into electrons in shocked matter is very inefficient. The total energy of GRBs becomes as large as >1055(ΔΩ/4π)ergs and hence a strong beaming of GRB emission is highly likely. There may also be TeV emission in afterglow phase from external shocks, and proton synchrotron in this phase gives a quantitative explanation for the famous long duration GeV emission from GRB 940217. Most TeV gamma-rays are absorbed in intergalactic space by interactions with the infrared and microwave background radiations, and finally form gamma-ray background in GeV range. This process may explain the extragalactic background radiation observed in the EGRET range. We also discuss absorption of TeV gamma-rays in the shocked region of GRBs by the γγ->e± process, which may provide a new channel for energy transfer from protons into electrons (and positrons). This process should be important for the energetics of GRBs.