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GRB 060206: hints of precession of the central engine?

Liu, X. W. and Wu, X. F. and Lu, T. (2008) GRB 060206: hints of precession of the central engine? Astronomy and Astrophysics, 487 (2). pp. 503-508. ISSN 0004-6361. doi:10.1051/0004-6361:20078783.

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Aims. The high-redshift (z=4.048) gamma-ray burst GRB 060206 showed unusual behavior, with a significant rebrightening by a factor of ~4 at about 3000 s after the burst. We argue that this rebrightening implies that the central engine became active again after the main burst produced by the first ejecta, then drove another more collimated jet-like ejecta with a larger viewing angle. The two ejecta both interacted with the ambient medium, giving rise to forward shocks that propagated into the ambient medium and reverse shocks that penetrated into the ejecta. The total emission was a combination of the emissions from the reverse- and forward- shocked regions. We discuss how this combined emission accounts for the observed rebrightening. Methods. We apply numerical models to calculate the light curves from the shocked regions, which include a forward shock originating in the first ejecta and a forward-reverse shock for the second ejecta. Results. We find evidence that the central engine became active again 2000 s after the main burst. The combined emission produced by interactions of these two ejecta with the ambient medium can describe the properties of the afterglow of this burst. We argue that the rapid rise in brightness at ~3000 s in the afterglow is due to the off-axis emission from the second ejecta. The precession of the torus or accretion disk of the central engine is a natural explanation for the departure of the second ejecta from the line of sight.

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Additional Information:© ESO 2008. Received 3 October 2007. Accepted 15 May 2008. We would like to thank the anonymous referee’s constructive comments and suggestions which improved our paper significantly. X.W. Liu thanks D.M. Wei for his encouragement to accomplish this work. We thank Y.F. Huang, Y.W. Yu, Y. Li and L. Shao for helpful discussions. This work was supported by the National Natural Science Foundation of China (grants 10473023, 10503012, 10621303, and 10633040). XFW gratefully acknowledges Re’em Sari during his visit to Caltech, also thanks the supports of China Postdoctoral Science Foundation, K.C. Wong Education Foundation (Hong Kong), and Postdoctoral Research Award of Jiangsu Province.
Funding AgencyGrant Number
National Natural Science Foundation of China10473023
National Natural Science Foundation of China10503012
National Natural Science Foundation of China10621303
National Natural Science Foundation of China10633040
China Postdoctoral Science FoundationUNSPECIFIED
K.C. Wong Education Foundation (Hong Kong)UNSPECIFIED
Postdoctoral Research Award of Jiangsu ProvinceUNSPECIFIED
Subject Keywords:gamma rays: bursts; gamma rays: theory; gamma rays: observations
Issue or Number:2
Record Number:CaltechAUTHORS:20090512-104916846
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14203
Deposited By: Tony Diaz
Deposited On:13 May 2009 18:38
Last Modified:08 Nov 2021 22:44

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