Intrinsic spectra and energetics of cosmological Gamma-Ray Bursts

We extend a previous work on the intrinsic spectral properties and energetics of GRBs with known redshift based on 12 BeppoSAX events by including in the sample a total of 10 more events detected either by BATSE, BeppoSAX or HETE-2. An indication of a trend of the total isotropic equivalent radiated energy, E_rad, with redshift is found and, remarkably, the previously found relationship between the peak energy of the rest-frame nuFnu spectrum, E_p,rest , and E_rad is confirmed and its significance increased. The implications of these results are briefly discussed in the framework of standard models for the prompt emission of GRBs.