Gomboc 2008 GRB 061126的详细观测

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· arXiv e-print (arXiv:0804.1727)

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Title:		Multiwavelength analysis of the intriguing GRB 061126: the reverse shock scenario and magnetization
Authors:		Gomboc, A.; Kobayashi, S.; Guidorzi, C.; Melandri, A.; Mangano, V.; Sbarufatti, B.; Mundell, C. G.; Schady, P.; Smith, R. J.; Updike, A. C.; Kann, D. A.; Misra, K.; Rol, E.; Pozanenko, A.; Castro-Tirado, A. J.; Anupama, G. C.; Bersier, D.; Bode, M. F.; Carter, D.; Curran, P.; Fruchter, A.; Graham, J.; Hartmann, D. H.; Ibrahimov, M.; Levan, A.; Monfardini, A.; Mottram, C. J.; O'Brien, P. T.; Prema, P.; Sahu, D. K.; Steele, I. A.; Tanvir, N. R.; Wiersema, K.
Publication:		eprint arXiv:0804.1727
Publication Date:		04/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Submitted to ApJ
Bibliographic Code:		2008arXiv0804.1727G

Abstract

We present a detailed study of the prompt and afterglow emission from Swift GRB 061126 using BAT, XRT, UVOT data and multi-color optical imaging from ten 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 min to 20 days after the burst, shows a simple power-law decay with $\alpha_{\rm X}=1.290\pm0.008$. 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 $\alpha_1=1.48\pm 0.06$ to $\alpha_2=0.89\pm0.03$) approximately 12 min after the burst. We suggest the early, steep component is due to a reverse shock and show that the original ejecta from the central engine is highly magnetized. 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 broad band 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. Possible chromatic break at 1.5 days after the burst would give support to the additional emission scenario.

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