THE HISTORY OF GRB OUTFLOWS: EJECTION LORENTZ FACTOR AND RADIATION LOCATION OF X-RAY FLARES
THE HISTORY OF GRB OUTFLOWS: EJECTION LORENTZ FACTOR AND RADIATION LOCATION OF X-RAY FLARES
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伽玛暴流出的历史：射出洛伦兹因子和X射线耀斑的辐射位置
DOI：
10.3847/0004-637x/831/1/111
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发表时间：
2016
影响因子：
4.9
通讯作者：
En-Wei Liang
中科院分区：
文献类型：
--
作者：
Hui-Jun Mu;Da-Bin Lin;Shao-Qiang Xi;Ting-Ting Lin;Yuan-Zhu Wang;Yun-Feng Liang;Lian-Zhong Lü;Jin Zhang;En-Wei Liang
利用Swift/X射线望远镜观测到的29个明亮的伽玛射线暴X射线耀斑的陡衰变段的时间分辨光谱，用曲率效应模型模拟了它们的光变曲线和光谱指数演化行为。结果表明，观测到的快速通量衰减和强谱指数随时间的演化可以很好地用该模型拟合，导出的特征时间尺度（tc）在23 ~ 264 s范围内。利用由瞬发γ射线导出的峰值亮度与洛伦兹因子之间的经验关系，我们估算了耀斑的洛伦兹因子（ΓX）。我们得到了ΓX = 17 <$87，中值为52，小于瞬发γ射线火球的初始洛伦兹因子。用导出的tc和ΓX约束了13个X射线耀斑的辐射区域，得到RX =（0.2 <$1.1）× 10 ~（16）cm，小于耀斑峰值时刻余辉火球的半径。将我们的结果与一个初始Lorentz因子可在文献中获得的GRB样本相结合，发现了一个从瞬发γ射线相到X射线相的长演化特征，即，.这些结果可能揭示了伽玛暴中心引擎的长期演变。
We present time-resolved spectral analysis of the steep decay segments of 29 bright X-ray flares of gamma-ray bursts (GRBs) observed with the Swift/X-ray telescope, and model their light curves and spectral index evolution behaviors with the curvature effect model. Our results show that the observed rapid flux decay and strong spectral index evolution with time can be well fitted with this model, and the derived characteristic timescales (tc) are in the range of 23 ∼ 264 s. Using an empirical relation between the peak luminosity and the Lorentz factor derived from the prompt gamma-rays, we estimate the Lorentz factors of the flares (ΓX). We obtain ΓX = 17 ∼ 87 with a median value of 52, which is smaller than the initial Lorentz factors of prompt gamma-ray fireballs. With the derived tc and ΓX, we constrain the radiating regions of 13 X-ray flares, yielding RX = (0.2 ∼ 1.1) × 1016 cm, which are smaller than the radii of the afterglow fireballs at the peak times of the flares. A long evolution feature from prompt gamma-ray phase to the X-ray epoch is found by incorporating our results with a sample of GRBs whose initial Lorentz factors are available in the literature, i.e., . These results may shed light on the long-term evolution of GRB central engines.