Testing Relativistic Boost as the Cause of Gamma-Ray Quasi-periodic Oscillation in a Blazar
Testing Relativistic Boost as the Cause of Gamma-Ray Quasi-periodic Oscillation in a Blazar
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测试相对论增强作为耀变体中伽马射线准周期振荡的原因
DOI：
10.3847/1538-4357/aae48a
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Wang Jiancheng
中科院分区：
文献类型：
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作者：
Yan Dahai;Zhou Jianeng;Zhang Pengfei;Zhu Qianqian;Wang Jiancheng
耀变体中伽马射线准周期振荡（QPO）的产生机制尚不清楚。一种可能性是几何模型，其中不需要固有的准周期变化，相对论多普勒因子周期性变化，导致观察到的伽马射线QPO。我们提出了一种方法来测试这个几何模型。我们分析了PG 1553+113从2008年8月到2018年2月的费米LAT数据。根据0.1-300 GeV能量范围内的29个四个月平均光谱能量分布，我们将费米LAT能量范围分为三个波段：0.1-1 GeV，1-10 GeV和10-300 GeV。在每个能量范围内的光谱可以成功地拟合的幂律。得到了三个能区的光变曲线和光子指数。然后，在三个狭窄的能量范围内的光变曲线，即，构造了0.2- 0.5GeV、2- 5GeV和20-40 GeV三个窄能区，并计算了这三个窄能区的相对变化幅度。对光曲线进行离散相关分析。结果表明：（1）在0.1GeV以上的能量范围内，光变曲线的变化规律与光变曲线的变化规律相同，（2）在0.1- 1GeV、1-10 GeV和10-300 GeV的能量范围内，三组光子指数基本保持不变;以及（iii）不同窄能量范围内的相对变化幅度之间的比率等于（在其误差内）通过多普勒效应的预测。我们的研究结果支持相对论助推产生的伽马射线QPO PG 1553+113的情况。
The mechanism for producing gamma-ray quasi-periodic oscillation (QPO) in blazars is unknown. One possibility is the geometric model, in which without the need for intrinsic quasi-periodic variation, the relativistic Doppler factor changes periodically, resulting in observed gamma-ray QPO. We propose a method to test this geometric model. We analyze the Fermi-LAT data of PG 1553+113 spanning from 2008 August until 2018 February. According to 29 four-month average spectral energy distributions in the energy range of 0.1–300 GeV, we split the Fermi-LAT energy range into three bands: 0.1–1 GeV, 1–10 GeV, and 10–300 GeV. The spectrum in each energy range can be successfully fitted by a power law. The light curves and photon indices in the three energy ranges are obtained. Then, light curves in three narrow energy ranges, i.e., 0.2–0.5 GeV, 2–5 GeV, and 20–40 GeV, are constructed, and the relative variability amplitudes in the three narrow energy ranges are calculated. A discrete-correlation analysis is performed for the light curves. Our results indicate that (i) the light curves in the different energy ranges follow the same pattern showed in the light curve above 0.1 GeV; (ii) the three groups of photon indices in the energy ranges of 0.1–1 GeV, 1–10 GeV, and 10–300 GeV keep nearly constant; and (iii) the ratio between relative variability amplitudes in different narrow energy ranges are equal (within their errors) to the prediction by the Doppler effect. Our results support the scenario of the relativistic boost producing the gamma-ray QPO for PG 1553+113.