ar X iv : a st ro - p h / 99 12 01 9 v 1 1 D ec 1 99 9 A jet - disk symbiosis model for Gamma

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 in a binary system which collapses to a black hole due to accretion. In our model we assume that a fraction of the initial energy due to this transition is deposited in the jet by magnetic fields. The observed emission is then due to an ultrarelativistic shock wave propagating along the jet. Good agreement with observational data can be obtained for systems such as the Galactic jet source SS433. Specifically, we are able to reproduce the typical observed afterglow emission flux, its spectrum as a function of time, and the fluence distribution of the corrected data for the 4B BATSE catalogue. We also studied the relation between the cosmological evolution of our model and the cosmic ray energy distribution. We used the Star Formation Rate (SFR) as a function of redshift to obtain the distribution in fluences of GRBs in our model. The fluence in the gamma ray band has been used to calculate the energy in cosmic rays both in our Galaxy and at extragalactic distances. This energy input has been compared with the Galactic and extragalactic spectrum of cosmic rays and neutrinos. We found that in the context of our model it is not possible to have any contribution from GRBs to either the extragalactic or the Galactic cosmic ray spectra.