Gamma-Ray Burst Energetics in the Swift Era
Gamma-Ray Burst Energetics in the Swift Era
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DOI：
10.1086/586693
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发表时间：
2007-07
期刊：
影响因子：
--
通讯作者：
D. Kocevski;N. Butler
中科院分区：
文献类型：
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作者：
D. Kocevski;N. Butler
我们研究了76个已知红移的伽马射线暴（GRB）的静止坐标能量学，这些伽马射线暴是由雨燕航天器探测到的，并由卫星的X射线望远镜（XRT）监测。利用Butler及其同事估计的辐射热通量值和每个事件的最后一次XRT观测，我们为它们的准直校正能量Eγ设置了一个下限，发现我们的样本中有68%的红移足够高和/或通量足够低，可以容纳在最后一次XRT观测之后发生的喷流破裂，并且仍然与雨燕前长伽玛暴的Eγ分布一致。我们发现，相对较少的剩余事件的X射线光变曲线显示晚时间的衰减斜率，这是一致的，从喷流中断后排放的预期的证据。X射线光变曲线中确实存在的突变往往比以前在光学光变曲线中观察到的突变更浅，并且发生得更早，产生的Eγ分布远低于雨燕前的分布。如果这些早期的X射线断裂不是由于喷流效应，那么我们的样本中有一小部分但很重要的部分具有较低的准直校正能量，使它们远高于雨燕前的Eγ分布。无论是哪种情况，对于长的宇宙学伽玛暴来说，与从雨燕前的观测中推导出的狭窄的标准能量相比，雨燕后的Eγ分布都必须要宽得多。我们注意到，几乎所有的雨燕前Eγ估计都来自于在光学中检测到的喷流破裂，而我们的样本完全限于X射线波长，进一步表明假设的喷流破裂的消色差可能不会延伸到高能量。
We examine the rest-frame energetics of 76 gamma-ray bursts (GRBs) with known redshift that were detected by the Swift spacecraft and monitored by the satellite’s X-Ray Telescope (XRT). Using the bolometric fluence values estimated by Butler and coworkers and the last XRT observation for each event, we set a lower limit to their collimation-corrected energy Eγ and find that 68% of our sample is at high enough redshift and/or low enough fluence to accommodate a jet break occurring beyond the last XRT observation and still be consistent with the pre-Swift Eγ distribution for long GRBs. We find that relatively few of the X-ray light curves for the remaining events show evidence for late-time decay slopes that are consistent with that expected from post-jet break emission. The breaks in the X-ray light curves that do exist tend to be shallower and occur earlier than the breaks previously observed in optical light curves, yielding a Eγ distribution that is far lower than the pre-Swift distribution. If these early X-ray breaks are not due to jet effects, then a small but significant fraction of our sample have lower limits to their collimation-corrected energy that place them well above the pre-Swift Eγ distribution. Either scenario would necessitate a much wider post-Swift Eγ distribution for long cosmological GRBs compared to the narrow standard energy deduced from pre-Swift observations. We note that almost all of the pre-Swift Eγ estimates come from jet breaks detected in the optical whereas our sample is limited entirely to X-ray wavelengths, furthering the suggestion that the assumed achromaticity of jet breaks may not extend to high energies.