The X-ray afterglow of GRB 081109A: clue to the wind bubble structure
Abstract
We present the prompt Burst Alert Telescope and afterglow X-ray Telescope data of Swift-discovered GRB 081109A up to ~5 × 105s after the trigger, and the early ground-based optical followups. The temporal and spectral indices of the X-ray afterglow emission change remarkably. We interpret this as the gamma-ray burst jet first traversing the freely expanding supersonic stellar wind of the progenitor with density varying as ρ ~ r-2. Then, after approximately 300 s the jet traverses into a region of apparent constant density similar to that expected in the stalled-wind region of a stellar wind bubble or the interstellar medium. The optical afterglow data are generally consistent with such a scenario. Our best numerical model has a wind density parameter A* ~ 0.02, a density of the stalled wind n ~ 0.12cm-3 and a transition radius ~4.5 × 1017 cm. Such a transition radius is smaller than that predicted by numerical simulations of the stellar wind bubbles and may be due to a rapidly evolving wind of the progenitor close to the time of its core-collapse.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2009
- DOI:
- 10.1111/j.1365-2966.2009.15555.x
- arXiv:
- arXiv:0903.4476
- Bibcode:
- 2009MNRAS.400.1829J
- Keywords:
-
- radiation mechanisms: non-thermal;
- ISM: jets and outflows;
- gamma-rays: bursts;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 7 pages, 5 figures, 2 tables, MNRAS accepted for publication