Hydrodynamic Time Scales and Temporal Structure in GRBs
Abstract
Description
We calculate the hydrodynamic time scales for a spherical ultra-relativistic shell that is decelerated by the ISM and discuss the possible relations between these time scales and the observed temporal structure in $γ$-ray bursts. We suggest that the bursts' duration is related to the deceleration time, the variability is related to the ISM inhomogeneities and precursors are related to internal shocks within the shell. Good agreement can be achieved for these quantities with reasonable, not fined tuned, astrophysical parameters. The difference between Newtonian and relativistic reverse shocks may lead to the observed bimodal distribution of bursts' durations.
5 page aps latex file with 1 EPS figure. Complete uuencoded compressed PS file is available at ftp://shemesh.fiz.huji.ac.il or at http://shemesh.fiz.huji.ac.il/papers/SaP_hunts.uu to appear in Proc. 3rd Huntsville Gamma--Ray Burst Symposium, eds. C. Kouveliotou, M.S. Briggs and G.J. Fishman, (New York:AIP)
5 page aps latex file with 1 EPS figure. Complete uuencoded compressed PS file is available at ftp://shemesh.fiz.huji.ac.il or at http://shemesh.fiz.huji.ac.il/papers/SaP_hunts.uu to appear in Proc. 3rd Huntsville Gamma--Ray Burst Symposium, eds. C. Kouveliotou, M.S. Briggs and G.J. Fishman, (New York:AIP)