arXiv 2007.005572020-07-01astro-ph.GAastro-ph.HE

活动星系核时间序列周期性的二维相关分析

Two-dimensional correlation analysis of periodicity in active galactic nuclei time series

Andjelka B Kovacevic, Luka C. Popovic, Dragana Ilic

备注：: accepted by Open astronomy

摘要：

活动星系核（AGN）是最强大的光源之一，具有固有的、显著的和随机的亮度变化。它们的时间序列的随机性是如此微妙，以至于模糊了非周期波动和噪声振荡之间的边界。这对分析这样的时间序列提出了挑战，因为视觉检查和预处理方法都不能很好地识别其中的振荡信号。因此，需要一种用于周期性检测的客观方法。在这里，我们回顾我们的一个新的数据分析方法，结合了二维相关（2D）的时间序列与强大的方法高斯过程。为了证明这种技术的实用性，我们将其应用到两个例子的问题，没有充分利用：阻尼rednoised人工时间序列模仿活动星系核的时间序列和新发表的观察到的时间序列的变化看活动星系核（CL活动星系核）NGC 3516。该方法成功地检测到这两种类型的时间序列的周期性。NGC 3516中$\sim 4$ yr的周期性使我们能够推测，如果在其吸积盘（AD）中形成的热不稳定性在类似于检测到的周期性的时间尺度上，那么AD半径可能是$\sim 0.0024$ pc。

英文摘要：

The active galactic nuclei (AGN) are among the most powerful sources with an inherent, pronounced and random variation of brightness. The randomness of their time series is so subtle as to blur the border between aperiodic fluctuations and noisy oscillations. This poses challenges to analysing of such time series because neither visual inspection nor pre-exisitng methods can identify well oscillatory signals in them. Thus, there is a need for an objective method for periodicity detection. Here we review our a new data analysis method that combines a two-dimensional correlation (2D) of time series with the powerful methods of Gaussian processes. To demonstrate the utility of this technique, we apply it to two example problems which were not exploited enough: damped rednoised artificial time series mimicking AGN time series and newly published observed time series of changing look AGN (CL AGN) NGC 3516. The method successfully detected periodicities in both types of time series. Identified periodicity of $\sim 4$ yr in NGC 3516 allows us to speculate that if the thermal instability formed in its accretion disc (AD) on a time scale resembling detected periodicity then AD radius could be $\sim 0.0024$ pc.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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