GRB1 - Photospheric Emission in GRBs
Early models of cosmological GRBs predicted the observed spectrum to be nearly blackbody. Observations were at odds with this prediction, and different theoretical models assuming optically thin emission have been put forward. However, models of such non thermal emission appear to be inconsistent with observations of steep spectra in early phases of many GRBs. Instead models involving photospheric emission producing modified blackbody spectra explain such observed spectra quite naturally.
We plan to discuss physical aspects of photospheric emission in ultrarelativistic sources as well as observational issues related to the detection of such a photospheric component in GRBs. Special attention is expected to be given to sub-photospheric dissipation mechanisms, geometric and dynamical effects, jet content, and additional components in the observed spectrum.