Astron. Astrophys. 324, L17-L20 (1997)

4. Conclusions

We have studied some of the conditions necessary for the explanation of gamma ray bursts as the interaction of the baryonic relativistic jet with the soft photon field in the dense star regions (Shaviv, Dar 1996). The main attractiveness of this model is that it is the only one that predicts the observable gamma ray burst profiles. We have found out two difficulties of these model, none of them being fatal but each of them putting strong restrictions on it. First of all, the main achievement of the model - the reproduction of the observational burst profiles - has seemed to be strongly sensitive to the jet front geometry. The shape of the peaks in the spherical case becomes more wide and asymmetric, and the number of the peaks becomes smaller.

The second is that it is hard to agree the theoretical event rate with the observed one. The neutron star merger rate in globular clusters and/or galactic nuclei should be high and the beaming of the jet should be small.

The spherical geometry is more consistent with the event rate than the plane one because it allows for beaming wider than , but is in worse agreement with the observed bursts profiles. The detailed investigation of the jet expansion geometry would allow now for the further treatment of this model of gamma ray bursts origin.

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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