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1 Introduction


A cosmological origin of GRBs leads to the conclusion of a huge energy output. If the identification with the galaxy having redshift z=3.42 is true, then in gamma radiation the energy release (without beaming) is $\sim 3 \ 10^{53}$ ergs (Kulkarni 1998). Note, that the solar rest mass is equal to $1.8 \ 10^{54}$ ergs. Small timescale indicates that GRBs are related to neutron stars and (or) stellar mass black holes. The common event from a collapse with a neutron star formation is a supernova explosion. The total energy release $E_{\rm tot}$ in a SN is equal to the binding energy of a neutron star $\sim 20\%~{\rm Mc}^2$. For the neutron star with a mass $1.4\,M_{\odot}$ we get $E_{\rm tot}\approx 5 \ 10^{53}$ ergs, which is comparable to the above estimate for a GRB. Only a small part $\sim 3 \ 10^{51}$ ergs is transformed into kinetic energy of the explosion, and the energy radiated in all parts of the electromagnetic spectrum is several tens times less. More then $99\%$of the total energy output is emitted in the form of weakly interacting neutrinos, and is dispersed in the Universe. An artificially constructed low-temperature structure around a neutron star or a black hole may suffer from an instability. Stars with a neutron core (Thorne-Zytkov model) are in most cases unstable to run-away neutrino emission, leading to radiation by neutrinos of more then $99\%$ of the accretion energy. Magnetorotational explosion, used by Pazcynski (1998) to explain the huge energy production in a cosmological GRB, had been suggested for the supernova explosion by Bisnovatyi-Kogan (1971). Numerical 1-D and 2-D calculations gave the efficiency of a transformation of the rotational energy into the kinetic one at the level of few percent (Ardelyan et al. 1997). The restrictions of the "hypernova" model of Pazcynski (1998) had been analyzed by Blinnikov & Postnov (1998). The total explosive energy output at the end of the evolution of a close binary, consisting of two neutron stars, suggested for a GRB model by Blinnikov at al. (1984) cannot exceed the value of a (positive) binding energy less than $10^{-3}M_{\odot}\ c^2= 1.6\ 10^{51}$ ergs (Saakyan & Vartanyan 1964). Only part of this energy may be radiated in the GRB region. In the presence of serious energy problems inherent in the model of the cosmological GRB, we try to explain the pioneering results of the afterglow measurements by Beppo-Sax, as well as previous hard gamma-ray afterglow observed by EGRET, in the frame of the model of GRB origin in the old nearby neutron stars inside the Galactic disk. The host galaxies with a high redshift are supposed to be a chance coincidence with GRB. Isotropy on the sky and non 3/2 $\log N/\log S$ may be connected with selection effects (Bisnovatyi-Kogan 1997), or a local non-uniformity (B.V. Komberg, priv. comm.).



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Up: Origin of GRB afterglows

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