By the direct comparison with the numerical integration of the complete relativistic hydrodynamical equations, the use of the constant-thickness approximation has been validated for values of the parameter . For the amount of energy released at transparency in the burst decreases, and its energy drifts toward low energy values, which are of little interest for the astrophysics of GRB. We conclude that the constant-thickness approximation is valid for all astrophysically relevant situations for the analysis of the GRB at transparency. Based on this validation we have studied the evolution of a PEM pulse in the presence of selected amounts of baryonic matter. We have studied for a typical case of EMBH and baryonic shell, the thermal, the bulk Lorentz factor evolution of the PEM pulse as well as the kinetic energy left over in the baryonic matter after the decoupling of matter and radiation and the emission of the GRB. Additional results corresponding to a larger range of masses and charges of the EMBH and the correlations between the peak energy and the duration of GRBs to be expected in our model will be considered in a future paper, together with the results of analyzing the interaction of the kinetic energy left over in the baryonic matter, after the decoupling of matter and radiation, with the interstellar medium.
© European Southern Observatory (ESO) 2000
Online publication: July 13, 2000