THE PHOTOSPHERIC RADIATION MODEL FOR THE PROMPT EMISSION OF GAMMA-RAY BURSTS: INTERPRETING FOUR OBSERVED CORRELATIONS

We show that the empirical Ep-L, Γ-L, Ep-Γ, and η-barγ-Ep correlations (where L is the time-averaged luminosity of the prompt emission, Ep is the spectral peak energy, Γ is the bulk Lorentz factor, and η-barγ is the emission efficiency of gamma-ray bursts, GRBs) are well consistent with the relations between the analogous parameters predicted in the photospheric radiation model of the prompt emission of GRBs. The time-resolved thermal radiation of GRB 090902B does follow the Ep-L and Γ-L correlations. A reliable interpretation of the four correlations in alternative models is still lacking. These may point toward a photospheric origin of prompt emission of some GRBs.