2003/05/08 by Andrei M. Beloborodov, Beloborodov, Andrei M.
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0305118
12 pages, invited talk at Niels Bohr Summer Institute, "Beaming and Jets in Gamma Ray Bursts"
arxiv created 2003/05/08 · arxiv updated 2009/12/01
The customary picture of the fireball deceleration by an external medium neglects two physical agents in the problem that are important at radii R<1017 cm: a radiative precursor (the prompt GRB) and a relativistic front of free neutrons. The radiative precursor preaccelerates the medium and loads it with e+- pairs. This provides a new explanation for the early optical flashes in GRBs. The front of free neutrons must form in a standard baryonic fireball and change the mechanism of the fireball deceleration. The neutron effect, however, disappears if the fireball is strongly dominated by the Poynting flux. The neutrons thus provide a unique link between the progenitor physics and the observed external blast wave. The explosion mechanism at R<1017 cm is testable with upcoming observations of early afterglows.