EVOLUTION OF THE SYNCHROTRON AND INVERSE COMPTON EMISSIONS OF THE LOW-ENERGY-PEAKED BL LAC OBJECT S5 0716+714
EVOLUTION OF THE SYNCHROTRON AND INVERSE COMPTON EMISSIONS OF THE LOW-ENERGY-PEAKED BL LAC OBJECT S5 0716+714
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DOI：
10.1088/0004-637x/713/1/180
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发表时间：
2010-03
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通讯作者：
Y. H. Zhang
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作者：
Y. H. Zhang
本文通过 XMM-Newton 于 2007 年 9 月 24 日至 25 日进行的长（~74 ks）X 射线观测，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。源头以小时为单位经历反复的耀斑。软 X 射线变化最多可达 4 倍，比硬 X 射线变化强得多。随着能量的增加，软 X 射线的变化幅度增大，但硬 X 射线的变化幅度减小。然而，硬X射线变异幅度实际上很大。我们第一次检测到软 X 射线变化和硬 X 射线变化之间有约 1000 秒的软滞后。能量差异越大，软滞后可能会变得越大。总体 X 射线光谱表现出较亮时较软的趋势，而软 X 射线光谱似乎表现出较亮时较硬的趋势。源的凹面X射线光谱可以解释为同步加速器发射的高能尾部（在软X射线中占主导地位）和逆康普顿（IC）发射的低能尾部（在硬X射线中贡献更大）的总和。同步加速器光谱是陡峭的（Г∼2.6），而IC光谱是平坦的（Г∼1.2）。同步加速器光谱似乎随着同步加速器通量的增加而变硬，而 IC 光谱似乎随着 IC 通量的增加而变软。当光源变亮时，同步加速器通量增加，但 IC 通量减少。与 IC 组件相比，同步加速器尾部表现出更大的通量变化，但光谱变化更小。当光源变亮时，两个分量之间的交叉能量和光谱能量分布 (SED) 的波谷能量会增加。 X 射线光谱变化表明，S5 0716+714 的同步加速器和 IC SED 峰值在变亮时会转向更高的能量。时间变化还表明源的硬 X 射线变化可能由同步加速器尾部主导。将使用 XMM-Newton 同时获得的光学和紫外数据与 X 射线观测结果进行比较。
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 ∼1000 s 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. The temporal variability also elucidates that the hard X-ray variations of the source might be dominated by the synchrotron tail. The simultaneous optical and UV data obtained with XMM-Newton are compared with the X-ray observations.