1998A&A...340..447M

We emphasize the already known idea that since GRB970508 released an energy of Q_γ≃10⁵¹δΩergs in soft gamma rays alone, where δΩ is the solid angle of the beam, the actual energy of the e⁺e^– p fireball driving the blast wave could be considerably higher than this value, Q_FB>Q_γ. We further argue that, for reasonably large values of δΩ, as is probably suggested by the radio observations, the value of Q_FB∼5x10⁵¹t_m³n₁erg, for GRB 970508; where n₁ is the number density of the ambient medium in units of 1 proton/cm³ and t_m is the epoch in months when the associated radio-blastwave degrades to become mildly relativistic. Thus the value of Q_FB for GRB 970508 could be as large as 10⁵³erg or even much higher. This idea is corroborated by GRB 971214 for which the value of Q_γ≃2x10⁵²δΩ is much higher than the corresponding value for GRB 970508. It is likely that GRB971214 has a correspondingly higher value of Q_FB. We discuss that it is unlikely that this energy, Q_FB∼10⁵³erg 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, the e⁺e^– p fireball (FB) driving the blast wave is likely to be preceded by a much stronger neutrino burst: ν+ν ->e⁺ +e^–. Although, the efficiency for e⁺ e^– production by this latter route is usually found to be as low as η_±∼10^–3, we point out that for very high values of neutrino energy release Q_ν>Q_FB, it is possible that, the value of η_± increses substantially. By considering that, the value of Q_FB for such GRBs is indeed ∼10⁵³erg, we envisage that the energy of the actual neutrino burst/wind could be as high as ∼10⁵⁴-10⁵⁵erg (here we ignore likely loss of energy by gravitational energy mode). This energy might be had from general relativistic collapse of a massive stellar core having initial gravitational mass, say, M_i∼few M_☉ 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 neutrino telescopes may detect neutrino burst of energy Q_ν∼10⁵⁴-10⁵⁵ ergs, with neutrino energies touching ∼1GeV, in coincidence with GRBs.