银河系中心VHE gamma-ray源HESS J1745-290的光谱和变率
Spectrum and variability of the Galactic Center VHE gamma-ray source HESS J1745-290
摘要：
使用来自H.E.S.S.的新数据对银河系中心（GC）区域的源HESS J1745-290的光谱和可变性进行了详细研究。切伦科夫望远镜阵列。研究了HESS J1745-290的耀斑活动和准周期振荡。结合半解析淋浴模型和基于统计矩的Hillas技术进行图像分析。根据谱形假设，用似然法计算了HESS J1745-290的光谱和光变曲线。H.E.S.S.的瑞利测试和傅立叶分析。GC信号被用来研究源的周期性。与以前的工作相比，统计增加了三倍，从一个简单的幂律谱的偏差是第一次检测到。在2004年、2005年和2006年三年的数据采集中测得的能谱与指数截止的幂律谱和破幂律谱都是兼容的。能谱的弯曲可能是光子源固有的，而不是星际吸收的影响。HESS J1745-290的伽马射线通量至少要增加两倍才能探测到一小时时间尺度的耀斑。在声称在X射线中检测到的周期内对可能的QPO活动进行的研究未显示H.E.S.S.中的任何周期性。信号了
英文摘要：
A detailed study of the spectrum and variability of the source HESS J1745-290 in the Galactic Center (GC) region using new data from the H.E.S.S. array of Cherenkov telescopes is presented. Flaring activity and Quasi Periodic Oscillations (QPO) of HESS J1745-290 are investigated. The image analysis is performed with a combination of a semi-analytical shower model and the statistical moments based Hillas technique. The spectrum and lightcurves of HESS J1745-290 are derived with a likelihood method based on a spectral shape hypothesis. Rayleigh tests and Fourier analysis of the H.E.S.S. GC signal are used to study the periodicity of the source. With three-fold increase in statistics compared to previous work, a deviation from a simple power law spectrum is detected for the first time. The measured energy spectrum over the three years 2004, 2005 and 2006 of data taking is compatible with both a power law spectrum with an exponential cut-off and a broken power law spectrum. The curvature of the energy spectrum is likely to be intrinsic to the photon source as opposed to effects of interstellar absorption. No significant flux variation is found. Increases in the gamma-ray flux of HESS J1745-290 by at least a factor of two would be required for a 3 sigma detection of a flare of time scales of an hour. Investigation of possible QPO activity at periods claimed to be detected in X-rays does not show any periodicities in the H.E.S.S. signal.
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