Photospheric emission from gamma-ray burst models with general dynamics and fits to Fermi LAT observations

I will present a model for gamma-ray bursts where dissipative photosphere provides the peak of the spectrum around MeV energies. This peak arises as synchrotron emission from around the photosphere. The initial acceleration depends on radius in a general way allowing for magnetic field and baryon dominated outflows. The GeV emission associated with GRBs observed by Fermi, arises as the interaction of photospheric radiation and the shocked electrons at the deceleration radius. We then fit the model spectrum to four GeV detected Fermi bursts and find that it gives a good description of the observations. If time permits, I will talk about GeV-TeV emission of a model with late energy injection. This is sometimes invoked to explain certain features of the X-ray afterglow, but it might give a contribution in the TeV range.

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