  Interaction of a fast shock wave generated during a supernova explosion with
a magnetized star-companion of the supernova precursor produces a current
sheet. We consider the evolution of this current sheet and show that a
singularity (shock) is formed in finite time within the ideal MHD framework.
Charged particles (electrons) are accelerated in the vicinity of the
singularity, and their distribution function has a plateau up to the energies
of the order of $10^4 mc^2$. These fast particles radiate in the $\gamma$-range
in the strong magnetic field of the current sheet ($B\simeq 10^6 G$). Radiation
is concentrated within a narrow angle around the current sheet, $\Delta\theta
\simeq 3\cdot 10^{-4}$, and its spectrum has the maximum at several hundreds of
$keV$. Presented calculations confirm the model of cosmological GRBs proposed
by Istomin & Komberg (2002).
