PKS 2155-304的出色VHE Gamma-Ray火炬
An Exceptional VHE Gamma-Ray Flare of PKS 2155-304
摘要：
红移z=0.116的高频率峰值BL Lac PKS 2155-304是一个众所周知的VHE（>100 GeV）伽马射线发射体。自2002年以来，其VHE通量一直使用H.E.S.S. S进行监测。在纳米比亚的成像大气切伦科夫望远镜的立体阵列。在2006年7月的黑暗时期，平均VHE通量被测量为从该物体观察到的典型值的十倍以上。本文仅关注2006年7月28日凌晨探测到的极端伽马射线爆发（MJD 53944）。在这次爆发中观测到的平均通量为I（>200 GeV）=（1.72 $\pm$ $0.05_{\rm stat}$ $\pm$ $0.34_{\rm syst}$）$\times$ 10 $^{-9}$ cm $^{-2}$ s $^{-1}$，相当于蟹状星云观测到的通量I（>200 GeV）的7倍。峰值通量测量一分钟的时间尺度分辨率在两倍以上的平均值。在傅立叶功率谱中可以看到高达~600 s的变化，并且观察到在~200秒的时间尺度上变化的良好分辨的爆发。数据中没有明显的光谱变异性迹象。假设发射区的大小相当于一个$^9 M_\odot$黑洞的史瓦西半径，则需要大于100的多普勒因子来适应观测到的变化时间尺度。
英文摘要：
The high-frequency peaked BL Lac PKS 2155-304 at redshift z=0.116 is a well-known VHE (>100 GeV) gamma-ray emitter. Since 2002 its VHE flux has been monitored using the H.E.S.S. stereoscopic array of imaging atmospheric-Cherenkov telescopes in Namibia. During the July 2006 dark period, the average VHE flux was measured to be more than ten times typical values observed from the object. This article focuses solely on an extreme gamma-ray outburst detected in the early hours of July 28, 2006 (MJD 53944). The average flux observed during this outburst is I(>200 GeV) = (1.72$\pm$$0.05_{\rm stat}$$\pm$$0.34_{\rm syst}$) $\times$ 10$^{-9}$ cm$^{-2}$ s$^{-1}$, corresponding to ~7 times the flux, I(>200 GeV), observed from the Crab Nebula. Peak fluxes are measured with one-minute time scale resolution at more than twice this average value. Variability is seen up to ~600 s in the Fourier power spectrum, and well-resolved bursts varying on time scales of ~200 seconds are observed. There are no strong indications for spectral variability within the data. Assuming the emission region has a size comparable to the Schwarzschild radius of a ~10$^9 M_\odot$ black hole, Doppler factors greater than 100 are required to accommodate the observed variability time scales.
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