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arXiv 0709.0262astro-ph
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窄线Seyfert 1 Ark 564的X射线定时特性中多个洛伦兹分量的发现

Discovery of multiple Lorentzian components in the X-ray timing properties of the Narrow Line Seyfert 1 Ark 564

I. M. McHardy, P. Arevalo, P. Uttley, I. E. Papadakis, D. P. Summons, W. Brinkmann, M. J. Page

备注：
11 pages, 11 figures, accepted for publication in MNRAS
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摘要：

本文给出了窄线Seyfert 1星系Ark~564的100 ksec XMM-牛顿观测的功率谱分析。当与早期的RXTE和ASCA观测相结合时，这些数据产生了一个覆盖70年频率的功率谱，该功率谱由具有两个非常明显的中断的幂律很好地描述。这种形状与迄今为止观测到的几乎所有其他活动星系核的功率谱不同，这些活动星系核只有一个检测到的破裂，并且类似于处于软状态的银河系双星系统。功率谱也可以很好地描述为两个洛伦兹形分量的总和，其中一个在较高频率处具有硬谱，类似于银河系双星系统中所看到的。以前，我们已经证明，相对于软带方舟564的硬带变化的滞后依赖于可变性的时间尺度，在银河系的二进制源。在这里，我们表明，可以很好地描述使用相同的两个洛伦兹模型描述的功率谱，假设每个洛伦兹分量有一个不同的时间滞后的时间尺度依赖的滞后。因此，所有的X射线定时证据都强烈地指向两个离散的局部区域，作为大多数变异性的起源。在银河系的X射线双星系统中，除了软态之外的大多数状态下，也就是在低硬态和中/极高态下，都可以看到类似的行为。鉴于方舟564的吸积速率非常高，最接近的类比是非常高（中间）状态，而不是低硬状态。因此，我们加强活动星系核和银河系双星源之间的比较超出了以前的研究，将其扩展到以前研究不足的非常高的吸积率制度。

英文摘要：

We present a power spectral analysis of a 100 ksec XMM-Newton observation of the narrow line Seyfert 1 galaxy Ark~564. When combined with earlier RXTE and ASCA observations, these data produce a power spectrum covering seven decades of frequency which is well described by a power law with two very clear breaks. This shape is unlike the power spectra of almost all other AGN observed so far, which have only one detected break, and resemble Galactic binary systems in a soft state. The power spectrum can also be well described by the sum of two Lorentzian-shaped components, the one at higher frequencies having a hard spectrum, similar to those seen in Galactic binary systems. Previously we have demonstrated that the lag of the hard band variations relative to the soft band in Ark 564 is dependent on variability time-scale, as seen in Galactic binary sources. Here we show that the time-scale dependence of the lags can be described well using the same two-Lorentzian model which describes the power spectrum, assuming that each Lorentzian component has a distinct time lag. Thus all X-ray timing evidence points strongly to two discrete, localised, regions as the origin of most of the variability. Similar behaviour is seen in Galactic X-ray binary systems in most states other than the soft state, i.e. in the low-hard and intermediate/very high states. Given the very high accretion rate of Ark 564 the closest analogy is with the very high (intermediate) state rather than the low-hard state. We therefore strengthen the comparison between AGN and Galactic binary sources beyond previous studies by extending it to the previously poorly studied very high accretion rate regime.

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