On the true energy budget of GRB970508 and 981214

Abstract

We emphasize a that since GRB970508 released an energy of Q_g~10^{51} \Omega ergs in soft gamma rays alone, the actual energy of the e^+e^- p FB driving the blast wave could be considerably higher than this value, Q_{FB} >Q_g. For reasonably large values of \Omega, as is probably suggested by the radio observations, the value of Q_{FB} ~ 5.10^{51}~t_m^3~n_1 erg, for GRB970508; here t_m is the epoch in months when the associated radio-blastwave degrades to become mildly relativistic. We discuss that it is unlikely that this energy, Q_{FB}~sim 10^{53}erg was liberated by the central engine by a direct electromagnetic mode. On the other hand, as conceived by several previous authors and as is suggested by supernova theories, their FB driving the blast wave is likely to be preceded by a much stronger neutrino burst: \nu + anti \nu- e^+ +e^-. Although, the efficiency for pair production by this latter route is usually found to be as low as ~.001, we point out that for very high values of neutrino energy release Q_\nu >Q_{FB}, it is possible that, its value increses substantially. By considering that, the value of $Q_{FB}$ for such GRBs is indeed ~sim 10^{53} erg, we envisage that the energy of the actual neutrino burst/wind could be as high as ~ 10^{54-55} erg. This energy might be had from general relativistic collapse of a massive stellar core having INITIAL gravitational mass, say, M_i~ few~M_sun to a stage having a potential well much deeper than what is present on a canonican neutron star surface. Accordingly, we predict that the new generation large nu elescopes may detect neutrino burst of energy ~10^{54-55} ergs, with neutrino energies touching ~ 1 GeV, in coincidence with GRBs.