Pub Date : 2018-02-16DOI: 10.3847/1538-4357/aae306
S. Frederick, E. Kara, C. Reynolds, C. Pinto, A. Fabian
A fraction of active galactic nuclei (AGN) exhibit dramatic variability, which is observed on timescales down to minutes in the X-ray band. We introduce the case study of 1H 1934-063 (z = 0.0102), a Narrow-line Seyfert 1 among the brightest and most variable AGN ever observed with XMM-Newton. This work includes spectral and temporal analyses of a concurrent XMM-Newton and NuSTAR 2015 observation lasting 130 kiloseconds, during which the X-ray source exhibited a steep (factor of ∼6) plummet and subsequent full recovery of the flux level, accompanied by deviation from a single log-normal flux distribution. We rule out Compton-thin obscuration as the cause for this dramatic variability observed even at NuSTAR energies. In order to constrain coronal geometry, dynamics, and emission/absorption processes, we compare a detailed spectral fitting with a Fourier-based timing analysis. Similar to other well-studied, highly variable Seyfert 1s, this AGN is X-ray bright and displays strong reflection features. We find a narrower broad iron line component compared to most Seyfert 1s, and constrain the black hole spin to be <0.1, one of the lowest yet discovered for such systems. Combined spectral and timing results are consistent with a dramatic change in the continuum on timescales as short as a few kiloseconds dictating the nature of this variability. We also discover a Fe–K time lag, measuring a delay of 20 s between relativistically blurred reflection off the inner accretion flow and the hard X-ray continuum emission.
一小部分活动星系核(AGN)表现出戏剧性的变化，这在x射线波段的时间尺度上可以观察到分钟。我们介绍了1H 1934-063 (z = 0.0102)的案例研究，它是XMM-Newton观测到的最亮、最多变的AGN之一。这项工作包括对XMM-Newton和NuSTAR 2015同时进行的持续130千秒的观测进行光谱和时间分析，在此期间，x射线源表现出急剧(约6倍)的下降，随后通量水平完全恢复，并伴随着偏离单一对数正态通量分布。我们排除了康普顿薄遮挡是造成这种戏剧性变化的原因，即使在核星能量下也能观察到。为了约束日冕几何、动力学和发射/吸收过程，我们将详细的光谱拟合与基于傅里叶的时序分析进行了比较。与其他被充分研究的，高度可变的Seyfert 1s类似，这个AGN是x射线明亮的，并显示出强烈的反射特征。与大多数Seyfert 1s相比，我们发现了更窄的宽铁线成分，并将黑洞自旋限制在<0.1，这是迄今为止发现的此类系统中最低的一个。综合光谱和时序结果与连续体在时间尺度上的剧烈变化一致，时间尺度短至几千秒，说明了这种变化的性质。我们还发现了Fe-K时间滞后，测量了内部吸积流的相对模糊反射和硬x射线连续体发射之间20秒的延迟。
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