  We consider gamma-ray burst models where the radiation is dominated by a
photospheric region providing the MeV Band spectrum, and an external shock
region responsible for the GeV radiation via inverse Compton scattering. We
parametrize the initial dynamics through an acceleration law Gamma \propto
r^\mu, with \mu between 1/3 and 1 to represent the range between an extreme
magnetically dominated and a baryonically dominated regime. We compare these
models to several bright Fermi LAT bursts, and show that both the time
integrated and the time resolved spectra, where available, can be well
described by these models. We discuss the parameters which result from these
fits, and discuss the relative merits and shortcomings of the two models.

High Energy Astrophysical Phenomena