2006年PKS 2155-304的一次壮观的VHE Gamma-Ray爆发
A Spectacular VHE Gamma-Ray Outburst from PKS 2155-304 in 2006
摘要：
自2002年以来，已经用高能立体系统（HESS）监测了高频峰值BL Lac PKS 2155-304的VHE（>100 GeV）伽马射线通量。在2006年7月28日凌晨探测到一次极端的伽马射线爆发（MJD 53944）。在这次爆发中观测到的200 GeV以上的平均通量是蟹状星云在相同阈值以上观测到的通量的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。假设发射区的大小与一个质量约为10^9太阳质量的黑洞的史瓦西半径相当，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：
Since 2002 the VHE (>100 GeV) gamma-ray flux of the high-frequency peaked BL Lac PKS 2155-304 has been monitored with the High Energy Stereoscopic System (HESS). An extreme gamma-ray outburst was detected in the early hours of July 28, 2006 (MJD 53944). The average flux above 200 GeV observed during this outburst is ~7 times the flux observed from the Crab Nebula above the same threshold. 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 solar mass black hole, Doppler factors greater than 100 are required to accommodate the observed variability time scales.
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