2014年2月1 ES 1011+496耀斑的MAGIC观测和随后的EBL密度约束
MAGIC observations of the February 2014 flare of 1ES 1011+496 and ensuing constraint of the EBL density
摘要：
2014年2月至3月，MAGIC望远镜在甚高能量（VHE，E> 100 GeV）下观测到处于耀斑状态的高频峰值BL Lac 1 ES 1011+496（z=0.212）。通量达到了比以前记录的任何源燃烧状态高10倍以上的水平。本文描述了耀斑的特征，给出了光变曲线、夜间光谱和全周期平均光谱的光谱参数。从这些数据中，我们的目标是检测的VHE光谱的源的河外背景光（EBL）的印记，以限制其在光学波段的强度。为此，我们实施了H.E.S.S.开发的方法。合作，其中源的固有能谱用简单函数建模，并且EBL诱导的光学深度使用模板EBL模型计算。然后最大化所观察到的光谱的可能性，包括自由参数之间的EBL不透明度的归一化因子。从所收集的数据中，产生了观测期间所有夜晚的微分能谱。评估拟合参数的变化，我们得出结论，大多数夜晚的光谱形状是兼容的，无论通量水平如何，这使我们能够产生一个平均光谱，从中可以限制EBL印记。似然比检验表明，EBL密度为1.07（-0.20，+0.24）_{stat+sys}的模型，相对于测试的EBL模板（Dominguez et al.2011）中的模型，在4.6 sigma水平上优于无EBL假设，假设内禀源谱可以建模为对数抛物线。这将转化为EBL密度在波长范围[0.24 um，4.25 um]内的约束，在1.4 um处的峰值为F=12.27 - 2.29 ^{+2.75} nW m^{-2} sr^{-1}，包括系统分类。
英文摘要：
In February-March 2014, the MAGIC telescopes observed the high-frequency peaked BL Lac 1ES 1011+496 (z=0.212) in flaring state at very-high energy (VHE, E>100GeV). The flux reached a level more than 10 times higher than any previously recorded flaring state of the source. We present the description of the characteristics of the flare presenting the light curve and the spectral parameters of the night-wise spectra and the average spectrum of the whole period. From these data we aim at detecting the imprint of the Extragalactic Background Light (EBL) in the VHE spectrum of the source, in order to constrain its intensity in the optical band. For this we implement the method developed by the H.E.S.S. collaboration in which the intrinsic energy spectrum of the source is modeled with a simple function, and the EBL-induced optical depth is calculated using a template EBL model. The likelihood of the observed spectrum is then maximized, including a normalization factor for the EBL opacity among the free parameters. From the data collected differential energy spectra was produced for all nights of the observed period. Evaluating the changes in the fit parameters we conclude that the spectral shape for most of the nights were compatible, regardless of the flux level, which enabled us to produce an average spectrum from which the EBL imprint could be constrained. The likelihood ratio test shows that the model with an EBL density 1.07(-0.20,+0.24)_{stat+sys}, relative to the one in the tested EBL template (Dominguez et al.2011), is preferred at the 4.6 sigma level to the no-EBL hypothesis, with the assumption that the intrinsic source spectrum can be modeled as a log-parabola. This would translate into a constraint of the EBL density in the wavelength range [0.24 um,4.25 um], with a peak value at 1.4 um of F=12.27_{-2.29}^{+2.75} nW m^{-2} sr^{-1}, including systematics.
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