Talk detail

Participant	Nymark, Tanja
Institution	Royal Institute of Technology - AlbaNova University Center - Stockholm - - Sweden

Session	GRB4	Accepted	Yes	Order	5	Time	15:15 - 15:45
Talk	Oral abstract	Title	The photosphere in GRBs as seen by Fermi
Co-authors
Abstract	Despite intense observational and theoretical investigation for more than 40 years the origin of the emission during the prompt phase of gamma ray bursts is still far from clear. Thanks to the high quality data provided by the Fermi Gamma Ray Space Telescope, our understanding of the observational characteristics of gamma ray bursts has improved greatly in recent years, but these observations have also revealed that the observed spectra of gamma ray bursts are far more complex than previously thought. Several gamma-ray bursts show evidence of emission from a jet photosphere, and there are indications that dissipation below the photosphere plays an important role in spectral formation also in other bursts. In this talk I will review the evidence for photospheric emission in gamma ray bursts observed by Fermi, with a focus on the strong bursts GRB090902B, GRB100724A and GRB110721A, and show how sub-photospheric dissipation can explain the non-thermal spectra of gamma-ray bursts.