论文标题
解释AGN中的中等UV/X射线相关性
Explaining the moderate UV/X-ray correlation in AGN
论文作者
论文摘要
长期以来，由于积聚磁盘的X射线照明，活性银河核（AGN）的UV/光学和X射线变异性长期以来一直很好地相关。然而，最近对附近AGN的监测活动发现，他们的X射线和紫外线/光学排放仅适度相关，从而挑战了上述范式。在这项工作中，我们旨在证明，由于互相关函数的定义，当考虑到X射线源的动态变异性时，在X射线照明的增强磁盘的情况下，较低的UV/X射线相关性是可以预期的。特别是，我们研究了X射线源的几何或物理配置的变异性如何影响预期的相关性。发现几何构型的变化会产生一系列UV/X射线互相关，它们符合观察到的值，而它们在紫外线和光学变异性之间导致高相关性，从而将观察到的结果与理论预测相吻合。我们得出的结论是，低UV/X射线相关性的检测与磁盘的X射线照明驱动的UV/光学变异性的假设并不矛盾，我们讨论了结果对相关研究的含义。
The UV/optical and X-ray variability of active galactic nuclei (AGN) have long been expected to be well correlated as a result of the X-ray illumination of the accretion disk. Recent monitoring campaigns of nearby AGN, however, found that their X-ray and UV/optical emission are only moderately correlated, challenging the aforementioned paradigm. In this work, we aim to demonstrate that due to the definition of the cross correlation function, a low UV/X-ray correlation is well expected in the case of an X-ray illuminated accretion disk, when the dynamic variability of the X-ray source is taken into account. In particular, we examine how the variability of the geometric or physical configuration of the X-ray source affects the expected correlation. Variations of the geometric configuration are found to produce a range of UV/X-ray cross correlations, which match well the observed values, while they result in high correlation between the UV and optical variability, reconciling the observed results with theoretical predictions. We conclude that the detection of a low UV/X-ray correlation does not contradict the assumption of the UV/optical variability being driven by the X-ray illumination of the disk, and we discuss the implications of our results for correlation studies.
