AAS 199th meeting, Washington, DC, January 2002
Session 12. Gamma Ray Bursts
Display, Monday, January 7, 2002, 9:20am-6:30pm, Exhibit Hall

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[12.02] A jet model for Gamma Ray Bursts: Cosmological implications

G. Pugliese (CfAO at UCSC), H. Falcke, P.L. Biermann (MPIfR), Y. Wang (Chinese Academy of Science)

We consider a jet-disk symbiosis model to explain GRBs, their afterglows, and their cosmological evolution.

In our model, 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. We use well established concepts and data from jets and disks in AGN and stellar binary systems, such as the Galactic jet source SS433. We propose that such sources are the precursors. The observed emission is due to synchroton emission from ultrarelativistic shock waves propagating along the jet; we can reproduce the typical observed afterglow emission flux and spectrum as a function of the time.

We use the Star Formation Rate (SFR) distribution as a function of the redshift to obtain the fluence distribution of GRBs (both long and short duration) in our model. We found that in the context of our model, it is close to impossible to have any contribution from GRBs to either the extragalactic or galactic cosmic rays. We obtain a very low predicted flux for the neutrino background.

As a further step, we distinguish between GRBs with long and short gamma ray emission durations. We investigate whether one of the two components could be more directly related with the SFR distribution and whether one of them could give a higher contribution than the other one to the galactic and extragalactic cosmic ray spectra. Our model can fit both components well, confirming that while long GRBs dominate in the soft region of the fluence distribution, the short ones are concentrated in the hard fluence region. The higher number of long GRBs detected compared with the short ones explains why in our model long GRBs give more contribution to the CR spectra.

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