A Reverse-Shock Model for the Early Afterglow of GRB 050525A
Abstract
The prompt localization of GRB 050525A by Swift allowed rapid follow-up of the afterglow. The observations revealed that the optical afterglow had a major rebrightening starting at ~0.01 days and ending at ~0.03 days, which was followed by an initial power-law decay. Here we show that this early emission feature can be interpreted as reverse-shock emission superposed by forward-shock emission in an interstellar medium environment. By fitting the observed data, we further constrain some parameters of the standard fireball-shock model: the initial Lorentz factor of the ejecta γ0>120, the magnetic energy fraction ɛB>4×10-6, and the medium density n<2 cm-3. These limits are consistent with those from other very early optical afterglows observed so far. In principle, a wind environment for GRB 050525A is disfavored.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2005
- DOI:
- 10.1086/466523
- arXiv:
- arXiv:astro-ph/0506139
- Bibcode:
- 2005ApJ...633.1027S
- Keywords:
-
- Gamma Rays: Bursts;
- Relativity;
- Shock Waves;
- Astrophysics
- E-Print:
- 11 pages, 1 figure, accepted for publication in ApJ