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D. Kazanas, M. Georganopoulos (NASA/Goddard Space Flight Center), A. Mastichiadis (Department of Astronomy, University of Athens, Greece)
We propose a process by which the kinetic energy of the protons, that carry most of the energy of GRB relativistic blast waves (RBW) of Lorentz factor \Gamma, is converted explosively into relativistic electrons of the same Lorentz factor, which subsequently produce the observed prompt \gamma-ray emission of the burst. This conversion is the result of the combined effects of the reflection of photons produced within the flow by upstream located matter, their re-interception and conversion into e+e--pairs on the RBW by the p \gamma ---> p e+e- reaction.
This procedure depends on kinematic and dynamic thresholds; the kinematic one reads \Gamma > (2/ b)1/5, where b is the magnetic field of the RBW in units of Bcr ~ 4.4 1013 G; the dynamic threshold reads Np \Gamma4 > 2, where Np is the column density of the post shock matter to the p \gamma ---> e+e- reaction; this latter condition is in effect that of the criticality of a nuclear pile, hence the terminology. It is shown that, when operating near threshold, the resulting GRB spectrum produces its peak luminosity at energy (in the lab frame) Ep ~\Gamma5 b ~mec2, thereby providing an answer to this outstanding question of GRBs.
Bulletin of the American Astronomical Society,
© 2003. The American Astronomical Soceity.