A comprehensive analysis of swift XRT data. II. Diverse physical origins of the shallow decay segment

	A comprehensive analysis of swift XRT data. II. Diverse physical origins of the shallow decay segment
	Liang, EW1,2 ; Zhang BB(张彬彬)1,3 ; Zhang, B1
刊名	ASTROPHYSICAL JOURNAL
	2007-11-20
卷号	670 期号:1 页码:565-583
关键词	gamma rays : bursts radiation mechanisms : nonthermal X-rays : general
ISSN号	0004-637X
通讯作者	Liang, EW (reprint author), Univ Nevada, Dept Phys & Astron, Las Vegas, NV 89154 USA.
产权排序	第三完成单位
英文摘要	The origin of the shallow decay segment in Swift XRT light curves remains a puzzle. We analyze the properties of this segment with a sample of 53 long Swift GRBs detected before 2007 February. We show that the distributions of the sample's characteristics are lognormal or normal, and its isotropic X-ray energy (E(iso),X) is linearly correlated with the prompt gamma-ray energy but with a steeper photon spectrum, aside from some X-ray flashes. No significant spectral evolution is observed from this phase to the following phase, and the latter is usually consistent with external shock models, implying that the shallow decay is also of external-shock origin, likely a refreshed external shock. Within the refreshed-shock model, the data are generally consistent with a roughly constant injection luminosity up to the end of this phase, t(b). A positive correlation between Eiso; X and tb also favors this scenario. Among the 13 bursts that have well-sampled optical light curves, six have an optical break around tb and the breaks are consistent with being achromatic. However, the other seven either do not show an optical break or have a break at an epoch different from tb. This raises a concern for the energy injection scenario, suggesting that the optical and X-ray emission may not be the same component, at least for some bursts. There are four significant outliers in the sample, GRBs 060413, 060522, 060607A, and 070110. The shallow decay phase in these bursts is immediately followed by a very steep decay after tb, which is inconsistent with any external-shock model. The optical data for these bursts evolve independently from the X-ray data. These X-ray plateaus likely have an internal origin and demand continuous operation of a long-term central engine. We conclude that the observed shallow decay phase likely has diverse physical origins.
学科主题	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
类目[WOS]	Astronomy & Astrophysics
研究领域[WOS]	Astronomy & Astrophysics
关键词[WOS]	GAMMA-RAY BURST ; AFTERGLOW LIGHT CURVES ; CONTINUOUS ENERGY INJECTION ; RELATIVISTIC WIND BUBBLES ; OPTICAL OBSERVATIONS ; MILLISECOND PULSARS ; THEORETICAL IMPLICATIONS ; SPECTRAL EVOLUTION ; LORENTZ FACTOR ; BLACK-HOLES
收录类别	SCI
原文出处	http://iopscience.iop.org/0004-637X/670/1/565/
语种	英语
WOS记录号	WOS:000250965400042
公开日期	2016-05-03
内容类型	期刊论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/7016]
专题	云南天文台_星系研究组
作者单位	1.Department of Physics and Astronomy, University of Nevada, Las Vegas, Las Vegas, NV 89154 2.Department of Physics, Guangxi University, Nanning, 530004 Guangxi, China 3.National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, Kunming, 650011 Yunnan, China
推荐引用方式 GB/T 7714	Liang, EW,Zhang BB,Zhang, B. A comprehensive analysis of swift XRT data. II. Diverse physical origins of the shallow decay segment[J]. ASTROPHYSICAL JOURNAL,2007,670(1):565-583.
APA	Liang, EW,Zhang BB,&Zhang, B.(2007).A comprehensive analysis of swift XRT data. II. Diverse physical origins of the shallow decay segment.ASTROPHYSICAL JOURNAL,670(1),565-583.
MLA	Liang, EW,et al."A comprehensive analysis of swift XRT data. II. Diverse physical origins of the shallow decay segment".ASTROPHYSICAL JOURNAL 670.1(2007):565-583.