Seyfert星系铁K α线的均方根变率特性
Rms variability properties of the iron K alpha line in Seyfert galaxies
摘要：
本文分析了XMM-牛顿观测的14个Seyfert星系的18个观测样本的均方根变率谱，这些样本具有足够的变率和信噪比，可以用来研究铁K波段的变化。在塞弗茨星系中普遍存在的6.4 keV的K α谱线的窄核显示出最小的可变性，并且总是比连续谱的可变性小，这支持了遥远物质（如环面）的起源。然而，至少有一半的观测确实显示了更宽的铁K波段变化的证据，并且至少有5种情况下，多余的线变化似乎很宽。最简单的预测-宽发射谱线和连续谱线一样可变-通常没有得到证实，因为只有两次观测显示了这种行为。在四种情况下，线的红翼比幂律连续体更易变，并向下延伸到~ 5 keV的能量。三个观测结果显示，线核的蓝向变化很强，也可能来自盘，但也可能是由于靠近核的其他热气体或光电离气体的发射或吸收。在存在这种过量蓝色变化的情况下，它并不总是在时间平均光谱中看到。六个观测结果在时间平均光谱中具有宽的铁谱线，但具有不变的红翼，其中三个在整个铁谱线区域没有变化。这表明连续谱和反射分量的解耦，可能是由于光弯曲或其他各向异性效应，如MCG-6-30-15和其他窄线塞弗特1所建议的。一个关键的结果是，像NGC 3516这样的天体的均方根光谱与模拟宽红翼的复杂吸收效应不一致。
英文摘要：
We present an analysis of the rms variability spectra of a sample of 18 observations of 14 Seyfert galaxies observed by XMM-Newton, which exhibit sufficient variability and signal-to-noise ratio to examine the variations in the iron K-band. The narrow core of the K alpha line at 6.4 keV, seen universally in Seyferts, shows minimal evidence for variability and is always less variable than the continuum, supporting an origin in distant material such as the torus. At least half the observations do show evidence for variations in the wider iron K-band, however, and in at least 5 cases the excess line variations appear to be broad. The simplest prediction -- that the broad emission line is as variable as the continuum -- is generally not confirmed as only two observations show this type of behaviour. In four cases, the red wing of the line is more variable than the power-law continuum and extends down to energies of ~ 5 keV. Three observations show strong variability blueward of the line core that could also be from the disk, but alternatively might be due to emission or absorption by other hot or photoionised gas close to the nucleus. In cases where this excess blue variability is present, it is not always seen in the time-averaged spectrum. Six observations possess a broad iron line in the time-averaged spectra but with an invariant red wing, and three of these six show no variability across the entire iron line region. This suggests a decoupling of the continuum and reflection component, perhaps due to light bending or other anisotropic effects as has been suggested for MCG-6-30-15 and other narrow-line Seyfert 1s. A key result is that the rms spectra of objects such as NGC 3516 do not agree with complex absorption effects mimicking the broad red wing.
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