Gamma Ray Bursts in the Fermi era: The spectral energy distribution of the prompt emission

Gamma Ray Bursts (GRBs) show evidence of different light curves, duration, afterglows, host galaxies and they explode within a wide redshift range. However, their spectral energy distributions (SEDs) appear to be very similar showing a curved shape. In 1993 Band et al. proposed a phenomenological description of the integrated spectral shape for the GRB prompt emission, the so called Band function. The data are well described by this function, however, the predictions based on this model for the gamma-ray emission of GRBs are not in agreement with the recent Fermi observations. Here we present an alternative scenario to explain the curved shape of GRB SEDs: the log-parabolic model.