SNI: a new mechanism for gamma ray burst. I.Weak magnetic field

Abstract

We propose a new mechanism for high energy gamma ray burst in Supernova type I (SNI) explosion. Presupernova is assumed to be a binary system comprised of a red giant and a white dwarf with a wind accretion. The accretion flow terminates by the accretion shock in the vicinity of the white dwarf at the distance of the order of the accretion radius. The gas inside the accretion radius constitutes the main body of a target for gamma ray production by $pp$ collisions.\par The supernova explosion and the shock propagation in the white dwarf result in the hydrodynamical acceleration of the outer layers of the star. The spectrum of accelerated particles is steep and the maximum energy does not exceed $1000$ $GeV$.\par The gamma ray burst is produced due to interaction of the accelerated particles with the gas in the binary system. Most of the photons have energies about $100$ $MeV$, the total number of the emitted photons is between $10^{46}$ and $10^{47}$. The gamma ray burst might have one or two precursors. The first one is produced during the shock breakout when the shock approaches the star surface and crosses it.\par The calculations are valid in the case of a weak magnetic field. The case of strong magnetic field will be considered in part II (in preparation).