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arXiv 1003.4794astro-ph.HE
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低能峰值BL Lac天体S5 0716+714的同步辐射和逆康普顿辐射的演化

Evolution of the synchrotron and inverse Compton emissions of the low energy peaked BL Lac object S5 0716+714

You-Hong Zhang

摘要:

本文详细分析了低能量峰值BL Lac天体S5 0716+714的时间和光谱变化,并在2007年9月24日至25日由XMM-牛顿进行了长X射线观测。源经历以小时为时间尺度的周期性耀斑。软X射线的变化,高达~4倍,比硬X射线的变化强得多。随着能量的增加,软X射线中的变化幅度增加,但在硬X射线中减小。然而,硬X射线的变化幅度实际上很大。这是我们第一次检测到软X射线和硬X射线变化之间约1000 s的软滞后。随着能量差的增大,软滞后可能变得更大。整个X射线光谱表现出一个软时亮的趋势,而软X射线光谱似乎显示出一个硬时亮的趋势。源的凹X射线谱可以解释为同步辐射的高能尾(在软X射线中占主导地位)和逆康普顿(IC)辐射的低能端(在硬X射线中贡献更多)的总和。同步辐射谱是陡的(Γ~2.6),而IC谱是平坦的(Γ~1.2)。同步辐射光谱似乎硬化与较大的同步辐射通量,而IC光谱似乎软化与较大的IC通量。当光源变亮时,同步辐射通量增加,而离子注入通量减小。同步加速器尾部具有较大的通量变化,但较小的光谱变化比IC组件。当光源变亮时,两个分量的交叉能量和谱能量分布的波谷能量增加。X射线光谱的变化表明,同步辐射和IC SED峰的S5 0716+714移动到更高的能量时,它变亮。

英文摘要:

This paper presents a detailed analysis of the temporal and spectral variability of the low-energy peaked BL Lac object S5 0716+714 with a long (~74 ks)X-ray observation performed by XMM-Newton on 2007 September 24-25. The source experiences recurrent flares on timescales of hours. The soft X-ray variations, up to a factor of ~4, are much stronger than the hard X-ray variations. With higher energy, the variability amplitude increases in the soft X-rays but decreases in the hard X-rays. The hard X-ray variability amplitude, however, is effectively large. For the first time, we detect a soft lag of ~1000s between the soft and hard X-ray variations. The soft lags might become larger with larger energy differences. The overall X-ray spectra exhibit a softer-when-brighter trend, whereas the soft X-ray spectra appear to show a harder-when-brighter trend. The concave X-ray spectra of the source can be interpreted as the sum of the high-energy tail of the synchrotron emission, dominating in the soft X rays, and the low-energy end of the inverse Compton (IC) emission, contributing more in the hard X-rays. The synchrotron spectra are steep (Γ~2.6), while the IC spectra are flat (Γ~1.2). The synchrotron spectra appear to harden with larger synchrotron fluxes, while the IC spectra seem to soften with larger IC fluxes. When the source brightens, the synchrotron fluxes increase but the IC fluxes decrease. The synchrotron tail exhibits larger flux variations but smaller spectral changes than the IC component does. The crossing energies between the two components and the trough energies of spectral energy distributions (SEDs) increase when the source brightens. The X-ray spectral variability demonstrates that the synchrotron and IC SED peaks of S5 0716+714 shift to higher energies when it brightens.

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