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arXiv 0705.1015astro-ph
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快速GRB余辉X射线光变曲线中的喷流间断

Jet-breaks in the X-ray Light-Curves of Swift GRB Afterglows

A. Panaitescu

备注：
7 pages, accepted by MNRAS, afterglows with lower limits on jet-break time added to Amati & Ghirlanda relations
发表信息：
Mon.Not.Roy.Astron.Soc.380:374-380,2007
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摘要：

在2005年1月至2007年3月期间由雨燕观测到的236个伽玛暴余辉中，我们确定了30个X射线光变曲线，其幂律衰减在触发后0.1-10天呈现出陡峭（“中断”），衰减比t^{-1.5}更陡。对于大多数这些余辉，X射线光谱斜率和衰减指数之前和之后的休息可以容纳的标准射流模型，虽然不能排除不同的起源的休息。此外，还有27个余辉的X射线光变曲线也可能表现出一个陡峭的衰变后期断裂，但证据并不那么令人信服。38个余辉的X射线发射在3天后才慢于t^{-1.5}，其中一半余辉在10天后才表现出这种慢衰减。因此，无论我们只计算每种类型的最强情况还是所有类型的最强情况，受到良好监测的雨燕余辉中有可能发生喷射中断的比例约为60%。这一比例与雨燕前余辉的75%相当，后者的光学光变曲线在约1天时显示出类似的中断。具有光变曲线突变的雨燕余辉的即时发射的性质显示出与先前发现的具有光变曲线突变的雨燕前光学余辉（分别为Amati和Ghirlanda关系）相同的相关性（GRB谱的峰值能量与爆发各向同性输出和爆发准直输出）。然而，我们发现，Ghirlanda关系在很大程度上是一个后果的Amati的和使用的喷气休息时间导致一个更强的Ghirlanda相关性只有当少数离群值的Amati关系被包括在内。

英文摘要：

In the set of 236 GRB afterglows observed by Swift between January 2005 and March 2007, we identify 30 X-ray light-curves whose power-law fall-off exhibit a steepening ("break") at 0.1-10 day after trigger, to a decay steeper than t^{-1.5}. For most of these afterglows, the X-ray spectral slope and the decay indices before and after the break can be accommodated by the standard jet model although a different origin of the breaks cannot be ruled out. In addition, there are 27 other afterglows whose X-ray light-curves may also exhibit a late break to a steep decay, but the evidence is not that compelling. The X-ray emissions of 38 afterglows decay slower than t^{-1.5} until after 3 day, half of them exhibiting such a slow decay until after 10 day. Therefore, the fraction of well-monitored Swift afterglows with potential jet-breaks is around 60 percent, whether we count only the strongest cases for each type or all of them. This fraction is comparable to the 75 percent of pre-Swift afterglows whose optical light-curves displayed similar breaks at ~1 day. The properties of the prompt emission of Swift afterglows with light-curve breaks show the same correlations (peak energy of GRB spectrum with the burst isotropic output and with burst collimated output) as previously found for pre-Swift optical afterglows with light-curve breaks (the Amati and Ghirlanda relations, respectively). However, we find that Ghirlanda relation is largely a consequence of Amati's and that the use of the jet-break time leads to a stronger Ghirlanda correlation only when the few outliers to the Amati relation are included.

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