Constraining the energy budget of GRB080721
Abstract
We follow the bright, highly energetic afterglow of Swift-discovered GRB080721 at z = 2.591 out to 36 d or 3 × 106s since the trigger in the optical and X-ray bands. We do not detect a break in the late-time light curve inferring a limit on the opening angle of and setting tight constraints on the total energy budget of the burst of Eγ >= 9.9 × 1051 erg within the fireball model. To obey the fireball model closure relations, the gamma-ray burst (GRB) jet must be expanding into a homogeneous surrounding medium and likely lies behind a significant column of dust. The energy constraint we derive can be used as an observational input for models of the progenitors of long GRBs: we discuss how such high collimation-corrected energies could be accommodated with certain parameters of the standard massive star core-collapse models. We can, however, most probably rule out a magnetar progenitor for this GRB which would require 100 per cent efficiency to reach the observed total energy.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2009
- DOI:
- 10.1111/j.1365-2966.2009.15443.x
- arXiv:
- arXiv:0812.2490
- Bibcode:
- 2009MNRAS.400...90S
- Keywords:
-
- gamma-rays: bursts;
- Astrophysics
- E-Print:
- 11 pages, 6 figures (3 colour), accepted for publication in MNRAS following minor revision of Sections 4.2 and 5