论文标题
探索X射线功率光谱与活性银核的能量光谱之间的联系
Exploring the Link between the X-ray Power Spectra and Energy Spectra of Active Galactic Nuclei
论文作者
论文摘要
活动的银河核（AGN）通常被认为是X射线二进制文件（XRBS）的缩放对应物。众所周知，XRBS X射线发射的功率谱密度（PSD）显示出具有光谱态的显着演化。但是，尚不清楚AGN是否遵循类似的进化趋势，尽管它们的X射线发射和PSD都是可变的。在这项工作中，我们研究了具有XMM-Newton多个长期观察结果的9个AGN样品，该样品表现出显着的X射线光谱变化。我们执行贝叶斯PSD分析以测量PSD形状和变异。我们发现，X射线能谱发生了很大的变化（主要是通量状态的变化）通常伴随着PSD形状的大变化。 PSD中高频断裂的出现也取决于光谱状态。在检测到明显高频PSD断裂的四个来源中，三个仅显示出高频率状态的突破，而其余的则仅显示仅在低频率状态下。此外，发现AGN的不同光谱状态的X射线RMS变异性变化多达1.0 dex。这些结果表明，观察到的不同变异性能可能是由不同光谱状态主导的不同物理过程引起的。我们的结果还表明，固有的PSD变化可以引入分散体的很大一部分，如各种X射线变异性能与黑洞质量之间的相关性报道。
Active Galactic Nuclei (AGN) are generally considered as the scaled-up counterparts of X-ray binaries (XRBs). It is known that the power spectral density (PSD) of the X-ray emission of XRBs shows significant evolution with spectral states. It is not clear whether AGN follow a similar evolutionary trend, however, though their X-ray emission and the PSD are both variable. In this work, we study a sample of nine AGN with multiple long observations with XMM-Newton, which exhibit significant X-ray spectral variation. We perform Bayesian PSD analysis to measure the PSD shape and variation. We find that a large change in the X-ray energy spectrum (mainly the change of flux state) is often accompanied by a large change in the PSD shape. The emergence of a high-frequency break in the PSD also depends on the spectral state. Among the four sources with significant high-frequency PSD breaks detected, three show the break only in the high-flux state, while the remaining one shows it only in the low-flux state. Moreover, the X-ray rms variability in different spectral states of an AGN is found to vary by as much as 1.0 dex. These results suggest that the different variability properties observed are likely caused by different physical processes dominating different spectral states. Our results also indicate that the intrinsic PSD variation can introduce a significant fraction of the dispersion as reported for the correlations between various X-ray variability properties and the black hole mass.
