Gamma-ray bursts in the Swift era
Gamma-ray bursts in the Swift era
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DOI：
10.1007/s10509-007-9551-3
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发表时间：
2007-07
影响因子：
1.9
通讯作者：
P. O’Brien;R. Willingale
中科院分区：
文献类型：
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作者：
P. O’Brien;R. Willingale
伽马射线暴是宇宙中最具能量的喷流和圆盘的组合。使用Swiftreveal进行的观察是一种复杂的时间和光谱行为。我们建议，这种行为可以用来完善伽玛射线暴的分类方案，并使其更好地与祖先类型。早期（瞬发）X射线光变曲线可以很好地描述为一个指数，松弛成幂律。指数律和幂律之间的过渡时间给出了一个定义明确的时间尺度Tp，我们使用它与瞬发辐射的光谱指数βp和瞬发幂律衰减指数α p来定义四种类型的爆发：短，慢，快和软。短爆发倾向于比长爆发更缓慢地下降。大多数伽玛暴显示第二个“余辉”成分，可以用类似于早期发射的方式拟合。在这第二个分量的衰变过程中，很少有伽玛暴显示出与雨燕前预测的雅阁一致的射流破裂。然而，最终余辉衰减的开始时间Ta与瞬发γ射线发射谱的峰值Epeak相关，其方式类似于光学“喷流中断”时间tj与Epeak之间的吉兰达关系。这些数据与简单的消色差喷流中断模型不一致，这使人们对使用后期时间中断来确定喷流准直的可靠性产生怀疑。
GRBs are the most energetic combination of jets and disks in the Universe. Observations made usingSwiftreveal a complex temporal and spectral behaviour. We propose that this behaviour can be used to refine the GRB classification scheme and align it better with progenitor types. The early (prompt) X-ray light curve can be well described by an exponential which relaxes into a power law. The transition time between the exponential and the power law gives a well-defined timescale,Tp, for the burst duration which we use with the spectral index of the prompt emission,βp, and the prompt power law decay index,αpto define four classes of burst: short, slow, fast and soft. Short bursts tend to decline more gradually than long bursts. Most GRBs display a second “afterglow” component which can be fitted in a similar way to the early emission. During the decay of this second component, few GRBs show jet breaks in accord with pre-Swiftpredictions. However, the start time of the final afterglow decay,Ta, correlates with the peak of the promptγ-ray emission spectrum,Epeak, in an analogous way to the Ghirlanda relation found between optical “jet-break” times,tj, andEpeak. These data are inconsistent with simple achromatic jet-break models casting doubt on the reliability of using late temporal breaks to determine the jet collimation.