High Energy Cosmic Rays, Gamma Rays And Neutrinos From Jetted GRBs

Abstract

Recent observations suggest that gamma ray bursts (GRBs) and their afterglows are produced in star formation regions in distant galaxies by highly relativistic jets that happen to point in our direction. Relativistic beaming collimates the emission from the highly relativistic jets into small solid angles along the jet direction. It implies that we are seeing only a small fraction of the events that produce GRBs. The observed GRB rate then requires an event rate which is comparable to the birth rate of neutron stars (NS). The highly relativistic jets sweep up ambient matter along their trajectories, accelerate it to cosmic ray (CR) energies and disperse it in hot spots which they form when they stop in the galactic halo. With an event rate comparable to the NS birth rate, such events in our Galaxy may be the main source of Galactic cosmic rays at all energies. Internal interactions and/or external interactions of these jets with high column density matter and/or radiation at their production sites or along their trajectories can produce high energy gamma rays and neutrinos that are highly beamed along the jet direction. Jetted GRBs, like blazars, may be much more fluent in high energy gamma rays and neutrinos than in MeV gamma rays. But, TeV gamma rays from large cosmological distances are unobservable because of their attenuation by electron-positron pair creation on the intergalactic infrared background radiation. However, high energy neutrinos from distant GRBs may be observed with large surface/volume telescopes which are under construction. TeV gamma rays and high energy neutrinos may also be detected from relatively nearby GRBs by the existing moderate size detectors, but with a much smaller rate.