. (2008) Multiwavelength analysis of the intriguing GRB 061126: the reverse shock scenario and magnetization. Astrophysical Journal, Volume 687 (Number 1). pp. 443-455. ISSN 0004-637X

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Abstract

We present a detailed study of the prompt and afterglow emission from Swift GRB 061126 using BAT, XRT, UVOT data and multicolor optical imaging from 10 ground-based telescopes. GRB 061126 was a long burst (T-90 = 191 s) with four overlapping peaks in its gamma-ray light curve. The X-ray afterglow, observed from 26 minutes to 20 days after the burst, shows a simple power-law decay with alpha(x) 1: 290 +/- 0:008. Optical observations presented here cover the time range from 258 s (Faulkes Telescope North) to 15 days ( Gemini North) after the burst; the decay rate of the optical afterglow shows a steep-to-shallow transition (from alpha(1) - 1.48 +/- 0:06 to alpha(2) - 0:88 +/- 0:03) approximately 13 minutes after the burst. We suggest the early, steep component is due to a reverse shock and show that the magnetic energy density in the ejecta, expressed as a fraction of the equipartition value, is a few 10 times larger than in the forward shock in the early afterglow phase. The ejecta might be endowed with primordial magnetic fields at the central engine. The optical light curve implies a late-time break at about 1.5 days after the burst, while there is no evidence of the simultaneous break in the X-ray light curve. We model the broadband emission and show that some afterglow characteristics (the steeper decay in X-ray and the shallow spectral index from optical to X-ray) are difficult to explain in the framework of the standard fireball model. This might imply that the X-ray afterglow is due to an additional emission process, such as late-time central engine activity rather than blast-wave shock emission. The possible chromatic break at 1.5 days after the burst would give support to the additional emission scenario.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Gamma ray bursts, Cosmology -- Observations
Journal or Publication Title:	Astrophysical Journal
Publisher:	IOP Publishing
ISSN:	0004-637X
Official Date:	1 November 2008
Volume:	Volume 687
Number:	Number 1
Number of Pages:	13
Page Range:	pp. 443-455
Identification Number:	10.1086/592062
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Royal Society (Great Britain), Slovenian Research Agency, Slovenia. Ministrstvo za visoko šolstvo, znanost in tehnologijo, Agenzia spaziale italiana [Italian Space Agency] (ASI), Research Councils UK, Particle Physics and Astronomy Research Council (Great Britain) (PPARC), United States. National Aeronautics and Space Administration (NASA), Science and Technology Facilities Council (Great Britain) (STFC)
Grant number:	1/011/07/0 (ASI)
URI:	http://wrap.warwick.ac.uk/id/eprint/29128

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