The discovery of non-linear X-ray variability in NGC 4051
The discovery of non-linear X-ray variability in NGC 4051
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NGC 4051 中非线性 X 射线变化的发现
DOI：
10.1046/j.1365-8711.1999.02370.x
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发表时间：
1999
影响因子：
4.8
通讯作者：
C. Done
中科院分区：
文献类型：
--
作者：
A. R. Green;I. McHardy;C. Done
我们给出了NGC4051的0.1-2keV X射线光曲线的功率谱分析。对两个长时间的ROSAT观测进行了分析，发现功率谱形状明显不同，表明该源在∼1年的时间尺度上不具有统计上的平稳性。也有强有力的证据表明，光曲线在某些时期是非线性的，这意味着功率谱不能充分代表光曲线中包含的所有信息。这些发现的意义深远，对研究活动星系核的X射线光曲线具有重要意义。目前流行的两个X射线可变性模型(多时间尺度散粒噪声和圆盘上的旋转耀斑)是线性的，因此不能完全描述数据：然而，可变性事件相关而不是随机的模型可能在描述观测到的光曲线方面更成功。
We present a power spectral analysis of the 0.1--2 keV X-ray light curves of NGC 4051. Two long ROSAT observations have been analysed and the power spectra are shown to have significantly different shapes, indicating that the source is not statistically stationary on time-scales of ∼ 1 year. There is also strong evidence that the light curve is non-linear at certain epochs, which means that the power spectra do not adequately represent all the information contained in the light curve. The implications of these discoveries are far reaching and fundamental to the study of the X-ray light curves of active galactic nuclei. The two currently popular models for X-ray variability (multi-time-scale shot noise and rotating flares on a disc) are linear, and so cannot fully describe the data: however, models in which the variability events are correlated rather than random may be more successful in describing the observed light curves.