The case for anisotropic afterglow efficiency within gamma-ray burst jets
Sep, 200510 pages
Published in:
- Astrophys.J.Lett. 641 (2006) L5-L8
e-Print:
- astro-ph/0509857 [astro-ph]
DOI:
Report number:
- SLAC-PUB-11514
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Abstract: (arXiv)
Early X-ray afterglows recently detected by {\it Swift} frequently show a phase of very shallow flux decay lasting from s up to s, followed by a steeper, more familiar decay. We suggest that the flat early part of the light curve may be a combination of the decaying tail of the prompt emission and the delayed onset of the afterglow emission observed from viewing angles slightly outside the edge of the region within the jet with prominent afterglow emission, as predicted previously. This would imply that a significant fraction of viewers get very little external shock energy along their line of sight, and, therefore, see a very high -ray to kinetic energy ratio at early times. The early flat phase in the afterglow light curve implies, in a rather robust and model independent manner, a very large -ray efficiency, typically , which is very difficult to extract from baryons by internal shocks.- gamma rays: bursts
- gamma rays: theory
- hydrodynamics
- X-rays: general
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