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arXiv 0707.2693astro-ph
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洛克曼洞V的XMM-牛顿观测:最亮AGN的时间变化

XMM-Newton observations of the Lockman Hole V: time variability of the brightest AGN

S. Mateos, X. Barcons, F. J. Carrera, M. J. Page, M. T. Ceballos, G. Hasinger, A. C. Fabian

摘要:

本文介绍了用XMM-Newton在Lockman Hole场中探测到的123个最亮天体(包括46个1型活动星系核和28个2型活动星系核)的X射线光谱和通量在月到年时间尺度上的变化。我们在~50%的天体中检测到了显著性> 3 σ的通量变化,其中包括68 ± 11%和48 ± 15%的1型和2型活动星系核样本。然而,我们发现,在我们的数据采样的时间尺度上,具有最佳质量光变曲线的源的比例> 80%,即绝大多数活动星系核的流量实际上可能在长时间尺度上发生变化。通量变化的平均相对固有振幅被认为是~0.15,尽管在测量值中具有较大的分散性,从~0.1到~0.65。我们的样本的活动星系核的流量变化特性并不显着依赖于红移或X射线光度的对象,似乎是相似的两种类型的活动星系核。使用宽带X射线颜色,我们发现显示显著性>3sigma的光谱可变性的源的分数为~40%,即比通量可变性更不常见。光谱变化在2型活动星系核中比在1型活动星系核中更为普遍,显著性> 99%。这一结果是一致的事实,即软发射的一部分,在2型活动星系核来自散射辐射,这一组成部分预计是少得多的变化比硬组件。我们观测到的天体的通量和光谱变化特性不能被解释为仅仅由一个光谱分量的变化产生,例如与质量吸积率变化相关的连续体形状的变化,或者X射线吸收量的变化。至少有两个光谱分量必须变化,以解释我们的对象的X射线可变性。

英文摘要:

This paper presents the results of a study of X-ray spectral and flux variability on time scales from months to years, of the 123 brightest objects (including 46 type-1 AGN and 28 type-2 AGN) detected with XMM-Newton in the Lockman Hole field. We detected flux variability with a significance >3sigma in ~50% of the objects, including 68+-11% and 48+-15% among our samples of type-1 and type-2 AGN. However we found that the fraction of sources with best quality light curves that exhibit flux variability on the time scales sampled by our data is >80%, i.e the great majority of the AGN population may actually vary in flux on long time scales. The mean relative intrinsic amplitude of flux variability was found to be ~0.15 although with a large dispersion in measured values, from ~0.1 to ~0.65. The flux variability properties of our samples of AGN do not significantly depend on the redshift or X-ray luminosity of the objects and seem to be similar for the two AGN types. Using a broad band X-ray colour we found that the fraction of sources showing spectral variability with a significance >3sigma is ~40% i.e. less common than flux variability. Spectral variability was found to be more common in type-2 AGN than in type-1 AGN with a significance >99%. This result is consistent with the fact that part of the soft emission in type-2 AGN comes from scattered radiation, and this component is expected to be much less variable than the hard component. The observed flux and spectral variability properties of our objects cannot be explained as being produced by variability of one spectral component alone, for example changes in the continuum shape associated with changes in the mass accretion rate, or variability in the amount of X-ray absorption. At least two spectral components must vary in order to explain the X-ray variability of our objects.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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