Astronomy And Astrophysics

. We consider a jet-disk symbiosis model to explain Gamma Ray Bursts and their afterglows. It is proposed that GRBs are created inside a pre-existing jet from a neutron star which collapses to a black hole due to massive accretion. In our model we assume that the initial energy due to this transition is all deposited in the jet by magnetic fields, using fully well explored concepts from jets and disks in active galactic nuclei and compact active stars in binary systems. The observed emission is then due to an ultrarelativistic shock wave propagating along the jet. We show that a good agreement between model predictions and observational data can be obtained for systems with accretion rates as high as in the Galactic jet source SS433. Specifically, we are able to reproduce the typical observed afterglow emission flux and its spectrum as a function of time. Key words: Gamma ray : bursts -- Shock waves -- ISM : jets and outflous -- Radiation mechanism : non-thermal 1. Introduction Gamma..