XMM-Newton Observations of a Possible Light Echo in the Seyfert 1 Nucleus of NGC 4051
XMM-Newton Observations of a Possible Light Echo in the Seyfert 1 Nucleus of NGC 4051
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NGC 4051 Seyfert 1 核中可能的光回波的 XMM-牛顿观测
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发表时间：
2002
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通讯作者：
T. Sasseen
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作者：
K. Mason;I. McHardy;M. Page;P. Uttley;F. Córdova;L. Maraschi;W. Priedhorsky;E. Puchnarewicz;T. Sasseen
我们讨论了一个1.5天的观测明亮的变量Seyfert 1星系NGC 4051，获得了X射线和紫外望远镜的XMM-牛顿和扩展的X射线波段使用罗西X射线定时探测器。紫外（2900 nm）和X射线（2-10 keV）光变曲线的峰-峰振幅分别为5%和~4倍。一个简单的带间互相关函数显示了三个广泛的特征：在滞后（Topt-TX射线）τ ~ +0.2天时，正相关系数rM = +0.63;在τ ~ +0.7天时，正相关系数rM = -0.65;由于光学和X射线数据的不对称采样，只能探测正滞后。蒙特卡洛模拟的基础上合成的不相关的光变曲线来自功率谱的真实的数据给出了一个~85%的信心，在这个水平上的功能。如果X射线和UV光曲线确实相关，则滞后是非常显著的（即，与零不一致），这暗示了X射线在离X射线源一定距离处被再处理成UV光的情况。一个简单的模型，其中的再处理器是一个倾斜的光学厚环在半径为0.14 LT-天的X射线源再现的UV数据以及。比较紫外和X射线波段的调制部分表明，2900流明通量的5%是以这种方式产生的。后处理场地足够靠近X射线发射器，以便从具有NGC 4051光度的源进行X射线加热，从而在UV波段产生增亮，并且所发射的UV通量的量表明后处理器的覆盖率约为6%。我们简要地讨论了后处理环结构的可能的物理性质。
We discuss a 1.5 day long observation of the bright variable Seyfert 1 galaxy NGC 4051 that was obtained with the X-ray and ultraviolet telescopes on XMM-Newton and extended in the X-ray band using the Rossi X-Ray Timing Explorer. The ultraviolet (2900 Å) and X-ray (2-10 keV) light curves varied with peak-to-peak amplitudes of 5% and a factor of ~4, respectively. A simple interband cross-correlation function shows three broad features: a positive correlation with coefficient rM = +0.63 at a lag (Topt - TX-ray) τ ~ +0.2 days, an anticorrelation with rM = -0.65 at τ ~ +0.7 days, and a broad but slightly weaker feature with rM ≥ 0.53 over τ = 1.2-1.4 days. Because of the asymmetric sampling of the optical and X-ray data, only positive lags could be probed. Monte Carlo simulations based on synthetic uncorrelated light curves derived from the power spectrum of the real data give an ~85% confidence in features at this level. If the X-ray and UV light curves are indeed correlated, the lag is highly significant (i.e., not consistent with zero), which is suggestive of a scenario in which X-rays are being reprocessed into UV light at a distance from the X-ray source. A simple model in which the reprocessor is an inclined optically thick ring at a radius of 0.14 lt-days from the X-ray source reproduces the UV data well. A comparison of the modulated fractions in the ultraviolet and X-ray bands suggests that 5% of the 2900 Å flux is produced in this way. The reprocessing site is close enough to the X-ray emitter for X-ray heating from a source with the luminosity of NGC 4051 to produce a brightening in the UV band, and the amount of UV flux emitted suggests that the covering fraction of the reprocessor is about 6%. We briefly discuss the possible physical nature of the reprocessing ring structure.