Kai Wang (China)
Kai.Wang @ mpi-hd.mpg.de
Multi-GeV gamma-ray in GRBs
Gamma-ray bursts (GRBs) are the brightest explosive phenomena in the universe, the study of which has been one of the most interesting fields in astrophysics. GRBs, likely associated with the births of stellar-size black holes or rapidly spinning, highly magnetized neutron stars, have been observed from all electromagnetic wavelengths and considered as potential emission sources of ultra-high energy cosmic rays, high-energy neutrinos and gravitational waves. Currently, fireball model, the most popular model of GRBs, assuming that a large amount of energy is released in a small space leading to production of gamma-rays, has gained, to a certain extent, a support regarding some aspects of GRBs. However, many features of GRBs still
remain a mystery, including the nature of the central engine, the composition of the GRB outflow, the jet configuration and composition, the properties of GRB environments, etc. In addition to these, High-energy gamma-rays in GRBs, often called as GeV photons, can be detected during both the prompt and afterglow stages of this phenomenon by the Large Area Telescope (LAT) on board the Fermi satellite, and they are still not clear either. Several mechanisms have been proposed to predict the origin of GeV photons along with the GRB prompt and afterglow phases, but it is still difficult to distinguish which one is more correct. Therefore the studies of GeV photons in GRBs contain unique information which would help us to understand the dynamics and radiative processes of GRBs, as well as derive an important information about the radiation fields in the intergalactic medium.
Supervisor: Felix Aharonian (MPIK)