We present the basic notions of the "Supercritical Pile" model of Gamma Ray Bursts (GRBs). This model is motivated by the need for a process that provides the dissipation necessary in GRBs and presents a well defined scheme for converting the energy stored in the relativistic protons of the Relativistic Blast Waves (RBW) associated with GRB into radiation; at the same time it leads to spectra which exhibit a peak in the burst νFν distribution at an energy Ep ≃ 1 MeV in the observer's frame, in agreement with observation and largely independent of the Lorentz factor Γ of the associated relativistic outflow.

Aims:We study the acceleration and radiation of charged particles in the shock waves of supernova remnants using a recent version of the "box model". According to this, particles are accelerated in an energy-dependent region around the shock by the first order Fermi mechanism and lose energy through radiation. Methods: The particle distribution function is obtained from a spatially averaged kinetic equation that treats the energy losses self-consistently. There exists also a second population that consists of those particles that escape behind the shock where they also radiate. The energy distribution of this population is calculated in a similar manner. Results: The application of the model to the supernova remnant RX J1713.7-3946, which was recently confirmed as a TeV source by HESS, shows that the X-ray emission can be attributed to electron synchrotron radiation while in γ-rays there are contributions from both electrons and protons, with protons playing the dominant role. Additionally, there are strong indications that particles diffuse in turbulence that has a Kolmogorov spectrum.