Oates 2007 双成分喷流解释GRB 050802

主要内容:
给出了余辉X射线和光学的观测结果，并用双成分的喷流模型解释。

精彩摘抄:


文章信息:
arXiv:0706.0669 [ps, pdf, other] : Title: The Two-Component Afterglow of Swift GRB 050802
Authors: S. R. Oates, M. De Pasquale, M.J. Page, A.J. Blustin, S. Zane, K. McGowan, K.O. Mason, T.S. Poole, P. Schady, P.W.A. Roming, K.L. Page, A. Falcone, N. Gehrels
Comments: 13 pages, 5 figures, accepted MNRAS

This paper investigates GRB 050802, one of the best examples of a it Swift gamma-ray burst afterglow that shows a break in the X-ray lightcurve, while the optical counterpart decays as a single power-law. This burst has an optically bright afterglow of 16.5 magnitude, detected throughout the 170-650nm spectral range of the UVOT on-board Swift. Observations began with the XRT and UVOT telescopes 286s after the initial trigger and continued for 1.2 x 10^6s. The X-ray lightcurve consists of three power-law segments: a rise until 420s, followed by a slow decay with alpha_2 = 0.63 +/- 0.03 until 5000s, after which, the lightcurve decays faster with a slope of alpha_3 = 1.59 +/- 0.03. The optical lightcurve decays as a single power-law with alpha_O = 0.82 +/- 0.03 throughout the observation. The X-ray data on their own are consistent with the break at 5000s being due to the end of energy injection. Modelling the optical to X-ray spectral energy distribution, we find that the optical afterglow can not be produced by the same component as the X-ray emission at late times, ruling out a single component afterglow. We therefore considered two-component jet models and find that the X-ray and optical emission is best reproduced by a model in which both components are energy injected for the duration of the observed afterglow and the X-ray break at 5000s is due to a jet break in the narrow component. This bright, well-observed burst is likely a guide for interpreting the surprising finding of Swift that bursts seldom display achromatic jet breaks.