Prompt emission spectra from the photosphere of a GRB

I explore the observational appearance of the photosphere of an ultrarelativistic flow with internal dissipation of energy (“dissipative” GRB model). As a case study, I use the magnetic reconnection model (AC model) that makes robust predictions on the energy dissipation rates at different radii in the flow. With analytical and numerical tools for the radiative transfer problem, I show that the flow develops a hot photosphere where inverse Compton scattering leads to highly non-thermal spectrum. For a wide range of luminosities and baryon loadings of the flow, this spectrum is very close to the observed prompt GRB emission. Its luminosity ranges from ∼ 3 to 20% of that of the total energy input.