论文标题
Blazar的可变性：非平稳性和Flux-RMS关系的研究
Blazar Variability: A Study of Non-stationarity and the Flux-RMS Relation
论文作者
论文摘要
我们使用软X射线望远镜在Astrosat和Archival XMM-Newton Data上观察到了Blazars MRK 421，PKS 2155-304和3C 273的X射线光曲线。我们使用所有三个Blazars的3-4个时期的长度为30-90 KS的光曲线。我们应用自回旋的集成运动平均值（ARIMA）模型，该模型表明可变性与大多数时期的短记忆过程一致。我们表明，在整个时期的不确定性中，单个Blazar的X射线变异性的功率谱密度（PSD）是一致的。这意味着使用来自不同时期的光曲线构建宽带PSD是准确的。但是，使用光曲线及其片段的方差的某些特性，我们表明，由于在某些观察结果中，由于其特征性的红噪声性质，因此，Blazars表现出非平稳性的提示。我们发现较短时间尺度上的可变性的根平方幅度与较长时间尺度的平均通量水平之间的线性关系，对于MRK 421的光曲线，跨时期的光曲线，数十年来，以及跨越5天和$ \ $ \ sim $ 10 yr的光曲线。在非常不同的时间尺度上的磁通量关系的存在可能意味着，与X射线二进制组和Seyfert星系相似，在Blazars中连接了较长和较短的时间尺度变异性。
We analyze X-ray light curves of the blazars Mrk 421, PKS 2155-304, and 3C 273 using observations by the Soft X-ray Telescope on board AstroSat and archival XMM-Newton data. We use light curves of length 30-90 ks each from 3-4 epochs for all three blazars. We apply the autoregressive integrated moving average (ARIMA) model which indicates the variability is consistent with short memory processes for most of the epochs. We show that the power spectral density (PSD) of the X-ray variability of the individual blazars are consistent within uncertainties across the epochs. This implies that the construction of broadband PSD using light curves from different epochs is accurate. However, using certain properties of the variance of the light curves and its segments, we show that the blazars exhibit hints of non-stationarity beyond that due to their characteristic red noise nature in some of those observations. We find a linear relationship between the root-mean-squared amplitude of variability at shorter timescales and the mean flux level at longer timescales for light curves of Mrk 421 across epochs separated by decades as well as light curves spanning 5 days and $\sim$10 yr. The presence of flux-rms relation over very different timescales may imply that, similar to the X-ray binaries and Seyfert galaxies, longer and shorter timescale variability are connected in blazars.
