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Interaction of GRB Fireballs with Ambient Medium

Andrei M. Beloborodov
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Abstract

The customary picture of the fireball deceleration by an external medium neglects two physical agents in the problem that are important at radii R<10^{17} 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<10^{17} cm is testable with upcoming observations of early afterglows.

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Andrei M. Beloborodov. 2003-05-08. Interaction of GRB Fireballs with Ambient Medium. https://arxiv.org/abs/astro-ph/0305118

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