Thermal and non-thermal emission during the prompt phase of GRBs

TYPEAstrophysics Seminar
Speaker:Dr. Asaf Pe'er
Affiliation:Harvard-Smithsonian Center for Astrophysics
Location:Lidow 605

The launch of Fermi opened a new era in the study of Gamma-Ray Bursts (GRBs) prompt emission. The broad band data show complex behavior that urge the need for a new interpretation. I will show that photospheric (thermal) emission is naturally expected. Light aberration in this relativistically expanding environment modifies the Planck spectrum that is expected to be observed as a multicolor black-body emission component. Moreover, these photons serve as seed photons for Compton scattering by energetic electrons, following kinetic energy dissipation above the photosphere. The high energy spectrum therefore results from various radiative processes, and as such is not easy to model. I will show how the analysis method proposed results in a complete, self consistent picture of the physical conditions at both emission sites of the thermal and non-thermal radiation. Furthermore, it enables a new insight into the physical conditions in the innermost regions of the outflow, hence constrain progenitor model.