Talk detail

Participant	Vurm, Indrek
Institution	The Hebrew University of Jerusalem - Edmond J. Safra Campus, Givat Ram - Jerusalem - Jerusalem - Israel

Session	GRB1	Accepted		Order	Time
Talk	Oral abstract	Title	Thermalization in GRB jets and peak energies of photospheric spectra
Co-authors
Abstract	An important question in photospheric GRB emission models concerns the ability of the jet to generate enough photons to keep the average energy per photon in agreement with observations. Dissipation below the Thomson photosphere alone is not sufficient, an efficient emission/absorption process is required in addition to scattering. We perform a systematic study of all processes that can be relevant for photon production and/or thermalization in GRB jets. We find that low-peaked spectra require a significant fraction of the available energy to be dissipated at a few×10^9 – a few×10^11 cm. The lower boundary of this range arises from the general blackbody constraint, while the upper boundary results from the rapid decline of photon production efficiency with radius due to the strong dependence on density. The bulk Lorentz factor in the thermalization zone is limited to at most 30, implying small kinetic energy and suggesting that energy is transported from the central engine by a Poynting-dominated jet.