  We present MCRaT, a Monte Carlo Radiation Transfer code for self-consistently
computing the light curves and spectra of the photospheric emission from
relativistic, unmagnetized jets. We apply MCRaT to a relativistic hydrodynamic
simulation of a long duration gamma-ray burst jet, and present the resulting
light-curves and time-dependent spectra for observers at various angles from
the jet axis. We compare our results to observational results and find that
photospheric emission is a viable model to explain the prompt phase of
long-duration gamma-ray bursts at the peak frequency and above, but faces
challenges in reproducing the flat spectrum below the peak frequency. We
finally discuss possible limitations of these results both in terms of the
hydrodynamics and the radiation transfer and how these limitations could affect
the conclusions that we present.
