Signatures of a Thermal Component in Shock-Accelerated Electrons in GRBs
by
Dimitrios Giannios(Princeton University)
→
Europe/Stockholm
Nordita seminar room (132:028)
Nordita seminar room (132:028)
Description
Recent particle-in-cell simulations suggest that a large fraction of the energy dissipated in a relativistic shock is deposited into a thermal distribution of electrons that is connected to the high-energy power-law tail. Here, we explore the observational implications of such a mixed thermal-nonthermal particle distribution for the afterglow and prompt emission of gamma-ray bursts. When the thermal component dominates the energy budget, the afterglow lightcurves show a very steep decline phase followed by a more shallow decay when the characteristic synchrotron frequency crosses the observed band. The steep decay appears in the X-rays at ~100 sec after the burst and is accompanied by a characteristic hard-soft-hard spectral evolution that has been observed in a large number of early afterglows. If internal shocks produce a similar mixed electron distribution, a thermal-like bump is expected at the synchrotron peak of the nu*f_nu spectrum.
