paper

A Characteristic Dense Environment or Wind Signature in Prompt GRB Afterglows

arXiv:astro-ph/0308409 · doi:10.1086/381733

Abstract

We discuss the effects of synchrotron self-absorption in the prompt emission from the reverse shock of GRB afterglows occurring in a dense environment, such as the wind of a massive stellar progenitor or a dense ISM in early galaxies. We point out that, when synchrotron losses dominate over inverse Compton losses, the higher self-absorption frequency in a dense environment implies a bump in the reverse shock emission spectrum, which can result in a more complex optical/IR light curve than previously thought. This bump is prominent especially if the burst ejecta is highly magnetized. In the opposite case of low magnetization, inverse Compton losses lead to a prompt X-ray flare. These effects give a possible new diagnostic for the magnetic energy density in the fireball, and for the presence of a dense environment.

arXiv comment11 pages, 2 figures, slightly expanded version of ApJL accepted paper

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