arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1607.02629astro-ph.GAastro-ph.HE
收藏

活动星系核的包绕X射线变率。II。超额方差和更新的结构函数

Ensemble X-ray variability of Active Galactic Nuclei. II. Excess Variance and updated Structure Function

F. Vagnetti, R. Middei, M. Antonucci, M. Paolillo, R. Serafinelli

备注：
9 pages, 13 figures, to appear on Astronomy and Astrophysics; v2 updated with language editing and a few clarifications about structure function
发表信息：
A&A 593, A55 (2016)
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

对活动星系核（AGN）X射线变率的研究大多集中在对单个邻近源的详细分析上。相对较少的研究已经处理了更一般的活动星系核人口在更广泛的区域的光度红移平面的合奏行为。我们想确定一个丰富的活动星系核样本的系综变率特性，该样本被称为多历元XMM偶发活动星系核样本（MEXSAS），它是从第五版XMM-牛顿偶发源目录（XMMSSC-DR 5）中提取的，红移在0.1和5之间，X射线光度在0.5-4.5 keV波段，在10^42和10^47 erg/s之间。我们敦促谨慎使用归一化超额方差（NXS），注意到如果使用不当，可能会导致低估变异性。我们使用结构函数（SF），更新了我们之前对较小样本的分析。我们提出了一个修正的NXS变异估计，占光变曲线持续时间在休息帧的基础上的知识，通过SF研究获得的变异行为。我们发现X射线可变性随静止帧时间滞后τ（τ ^[0.12]）的总体增加。我们证实了对X射线光度的反向依赖关系，近似为L_X^-0.19。我们分析了不同X射线波段的SF，发现变异性对频率的依赖性为nu^-0.15，对应于越亮越软的趋势。反过来，这种依赖性使我们能够参数化地校正在休息帧中的帧间频带中估计的可变性，从而导致适度的上移（V校正）。活动星系核的包绕X射线变率可用结构函数来描述。不适当地使用标准化超额方差可能会导致低估内在变异性，因此必须对数据或模型进行适当的校正以防止这些影响。

英文摘要：

Most investigations of the X-ray variability of active galactic nuclei (AGN) have been concentrated on the detailed analyses of individual, nearby sources. A relatively small number of studies have treated the ensemble behaviour of the more general AGN population in wider regions of the luminosity-redshift plane. We want to determine the ensemble variability properties of a rich AGN sample, called Multi-Epoch XMM Serendipitous AGN Sample (MEXSAS), extracted from the fifth release of the XMM-Newton Serendipitous Source Catalogue (XMMSSC-DR5), with redshift between 0.1 and 5, and X-ray luminosities in the 0.5-4.5 keV band between 10^42 and 10^47 erg/s. We urge caution on the use of the normalised excess variance (NXS), noting that it may lead to underestimate variability if used improperly. We use the structure function (SF), updating our previous analysis for a smaller sample. We propose a correction to the NXS variability estimator, accounting for the light curve duration in the rest frame on the basis of the knowledge of the variability behaviour gained by SF studies. We find an ensemble increase of the X-ray variability with the rest-frame time lag tau, given by tau^0.12. We confirm an inverse dependence on the X-ray luminosity, approximately as L_X^-0.19. We analyse the SF in different X-ray bands, finding a dependence of the variability on the frequency as nu^-0.15, corresponding to a softer when brighter trend. In turn, this dependence allows us to parametrically correct the variability estimated in observer-frame bands to that in the rest frame, resulting in a moderate shift upwards (V-correction). Ensemble X-ray variability of AGNs is best described by the structure function. An improper use of the normalised excess variance may lead to an underestimate of the intrinsic variability, so that appropriate corrections to the data or the models must be applied to prevent these effects.

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。

↑