Correlation and time delays of the X-ray and optical emission of the Seyfert Galaxy NGC 3783
Correlation and time delays of the X-ray and optical emission of the Seyfert Galaxy NGC 3783
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Seyfert Galaxy NGC 3783 的 X 射线和光学发射的相关性和时间延迟
DOI：
10.1111/j.1365-2966.2009.15110.x
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发表时间：
2009
影响因子：
4.8
通讯作者：
Arévalo P
中科院分区：
文献类型：
--
作者：
Arévalo P
我们同时展示了Seyfert星系NGC 3783的x射线和光学b波段和v波段的光曲线，跨度为2年。各波段的通量变化很大，波动具有显著的相关性。正如前面Stirpe等人所示，光学波段同时变化，其延迟小于1.5 d，但两个波段都滞后于x射线波动3-9 d。该延迟指向x射线再处理产生的光学变化，延迟值使再处理器靠近宽线区域。然而，光曲线的功率谱分析表明，x射线变异性在时间尺度为~ 2.9 d时呈幂律形状弯曲，斜率更陡，而光学波段的变异性振幅继续向覆盖的最长时间尺度（~ 300 d）增长。我们表明，功率谱和时间延迟的小值与x射线再处理产生的光学变异性的图像不一致，尽管振幅小，这种方式可能产生快速的光学波动。我们在长时间尺度上探测到光学波段比x射线波段更大的变化幅度。这一行为与最近从至少三个其他活动星系核获得的类似结果相一致，并表明在发光的吸积盘中存在长期光学变化的单独来源，可能是吸积率或热波动。
We present simultaneous X-ray and opticalB- andV-band light curves of the Seyfert Galaxy NGC 3783 spanning 2 years. The flux in all bands is highly variable and the fluctuations are significantly correlated. As shown before by Stirpe et al. the optical bands vary simultaneously, with a delay of less than 1.5 d but bothBandVbands lag the X-ray fluctuations by 3–9 d. This delay points at optical variability produced by X-ray reprocessing and the value of the lag places the reprocessor close to the broad-line region. A power spectrum analysis of the light curve, however, shows that the X-ray variability has a power-law shape bending to a steeper slope at a time-scale of ∼2.9 d while the variability amplitude in the optical bands continues to grow towards the longest time-scale covered, ∼300 d. We show that the power spectra together with the small value of the time delay are inconsistent with a picture whereallthe optical variability is produced by X-ray reprocessing, though the small amplitude, rapid optical fluctuations might be produced in this way. We detect larger variability amplitudes on long time-scales in the optical bands than in the X-rays. This behaviour adds to similar results recently obtained for at least three other active galactic nuclei and indicates a separate source of long-term optical variability, possibly accretion rate or thermal fluctuations, in the optically emitting accretion disc.