Mukul Bhattacharya, UT-Austin

"Photospheric emission model for explaining Gamma-Ray Burst (GRB) prompt emission"

Abstract: Although the observed spectra for the GRB prompt emission is well constrained, the underlying radiation mechanism is not very well understood. We explore the photospheric emission model by studying the Comptonization of fast cooled synchrotron photons below the photosphere when the electrons and protons are accelerated to relativistic energies by repeated dissipative events. Unlike previous simulations, we implement realistic photon to electron number ratio ~1e5 that is consistent with the observed radiative efficiency in addition to incorporating continuous energy transfer to electrons through Coulomb collisions. Using our Monte-Carlo code, we have successfully generated the observed GRB emission spectrum for electrons accelerated to highly relativistic energies with Lorentz factor ~100 by dissipative events ~40 in number, starting from moderate values of optical depth ~20. We find that the shape of the photon spectrum is independent of the initial photon energy distribution and baryonic energy content of the jet and hence independent of the emission mechanism.