Highly Energetic Physical Processes and Mechanisms for Emission from Astrophysical Plasmas: IAU Symposium 195
Highly Energetic Physical Processes and Mechanisms for Emission from Astrophysical Plasmas: IAU Symposium 195
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天体物理等离子体发射的高能物理过程和机制：IAU 研讨会 195
DOI：
10.1086/316487
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发表时间：
2000
影响因子：
3.5
通讯作者：
S. Tsuruta
中科院分区：
文献类型：
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作者：
S. Tsuruta
近30年来，伽玛暴的起源一直是个谜。它们的源在短时间尺度上发出巨大的能量，并且该过程涉及极端的相对论运动，其体积洛伦兹因子至少为几百。在过去的两年中，在X射线，光学，红外和无线电中的“余辉”发射被检测到。余辉可以在几秒钟的伽玛射线暴之后的几个月甚至几年内测量。我们回顾了，射线发射和余辉的理论，并表明，这些都得到了观测的有力支持。最近检测到的光发射同时与伽玛暴同意与理论预测，并进一步约束模型的自由参数。我们讨论的证据表明，一些突发的射流，并讨论偏振测量的前景。1.极端相对论运动和类属图像伽玛暴现象是近30年前由船帆座防御卫星发现的（Klebesadel，Strong，& Olson 1973）。今天，最大的伽马射线暴目录（Mesquesas等人，1999年）是由康普顿伽马射线天文台上的BATSE仪器记录的。BATSE每天观测到一次爆发，到目前为止已经观测到两千多次爆发。伽玛暴的光谱可以用破幂定律来描述，通常峰值在100-400 keY之间（Band等，1993）。在强烈的爆发中，可以看到延伸到200 MeV的高能幂律尾，在最极端的情况下可以检测到几个GeV的光子。平均而言，高能尾的特征是uF; rv v-0.25。伽玛暴的持续时间变化很大，主要在几毫秒到几百秒之间。持续时间的分布是双峰的：大约四分之一的爆发是“短”的，持续不到2秒，而大多数是“长”的。伽玛暴的一个显著特性是其不稳定的时间结构。虽然只有少数爆发是平滑的，但它们中的大多数在比爆发的持续时间t短得多的时间尺度~t上变化。在许多爆发中，比率N == t/~t是100或更大。由BATSE获得的爆发在天空中的分布是非常均匀的。具体来说，在银道面的方向上没有过多的爆发。最简单的解释是，爆发起源于宇宙学距离。到目前为止，宇宙学距离尺度已经很好地建立起来，因为红移已经被测量了超过少数的爆发。
The origin of GRBs has been a mystery for almost 30 years. Their sources emit a huge amount of energy on short time scales, and the process involves extreme relativistic motion with a bulk Lorentz factor of at least a few hundred. In the last two years, "afterglow" emission in Xray, optical, IR, and radio was detected. The afterglow can be measured up to months and even years after the few-seconds GRB. We review the theories for the ,-ray emission and its afterglow, and show that these are strongly supported by observations. A recent detection of optical emission simultaneous with the GRB agrees well with theoretical predictions and further constrains the free parameters of the models. We discuss the evidence that some of the bursts are jets and discuss the prospects of polarization measurements. 1. Extreme Relativistic Motion and the Generic Picture The phenomenon of GRBs was discovered almost thirty years ago by the Vela defense satellites (Klebesadel, Strong, & Olson 1973). Today, the largest catalog of GRBs (Paciesas et al. 1999) is due to the instrument BATSE onboard the Compton Gamma-ray Observatory. BATSE observes about one burst per day, and more than two thousands bursts have been observed by now. The spectrum of GRBs is well described by a broken power law and usually peaks between 100-400 keY (Band et al. 1993). In strong bursts, high-energy power law tails extending up to 200 MeV were seen, and several photons of a few GeV were detected in the most extreme case. On the average, the highenergy tail is characterized by uF; rv v-O.25 • The durations of the GRBs vary significantly, mainly between a few milliseconds to a few hundred seconds. The duration distribution is bimodal: about a quarter of the bursts are "short", lasting less than 2 seconds, while the majority are "long". One of the striking properties of GRBs is their erratic temporal structure. While only a few bursts are smooth, most of them vary over a time scale ~t which is much shorter than the burst's duration t. In many bursts, the ratio N == t/~t is a hundred or more. The distribution of bursts over the sky, as obtained by BATSE, is extremely uniform. Specifically, there is no excess of bursts in the direction of the galactic plane. The simplest explanation is that the bursts originate from cosmological distances. By now, the cosmological distance scale is well established since redshifts have been measured for more than a handful of bursts.