Speaker
Description
Recent observations of TeV emission from Gamma-Ray Bursts (GRBs)
demonstrated with certainty that it belongs to the afterglow phase. Afterglows' emission from radio frequencies to GeV gamma-rays is of synchrotron origin, whereas the TeV component is produced via distinct physical process (inverse Compton). Thus, TeV observations open an entirely new window into physics of relativistic shocks. We discuss three best studied TeV GRBs (190114C, 190829A, and 221009A); each of them observed at different evolutionary stage. GRB 190114C was an example of early afterglow (few minutes since the trigger), and GRB 190829A was observed much later, beginning from 4 hours after the trigger. Although two GRBs belong to distant evolutionary stages, their parameters (determined from broad-band spectra) fit nicely into predictions of pair-balance model of relativistic shocks. GRB 221009A is a unique example of TeV afterglow observed simultaneously with the prompt emission. In this case the parameters of afterglow only allow order-of-magnitude estimates, but again the values predicted by
the pair-balance model are consistent with observations. The lightcurve of this GRB was measured over the entire duration of the prompt phase. This allows one to check models intended to describe hydrodynamic evolution of external blast wave with intermittent energy supply. We present such a model, tested against observations. Our best-fitting solution for GRB 221009A is a surprisingly narrow jet with an opening angle of the order of 0.07 deg propagating into a wind-like external medium.
