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arXiv 0801.2598astro-ph
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活动星系核的X射线变率振幅与黑洞质量之间的反相关是内在的吗？

Is the anti-correlation between the X-ray variability amplitude and black hole mass of AGNs intrinsic?

Yuan Liu, Shuang Nan Zhang

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3 pages, 3 figures, 2 tables, accepted for publication in A&A (Research Note)
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摘要：

目标。活动星系核的黑洞质量和X射线光度都与X射线光变曲线的归一化超额方差（$σ_{\rm rms}^2 $）反相关。我们研究与$σ_{\rm rms}^2 $的哪种相关性是内在的相关性。方法.我们将33个活动星系核的完整样本（O' Neill et al.2005）分成两个子样本。子样本1中17个天体的黑洞质量由混响映射或恒星速度色散确定。其余16个天体的黑洞质量是根据宽线区半径与光学光度之间的关系估算的（子样本2）。然后分别对全样本和子样本进行偏相关分析、普通最小二乘回归和K-S检验。结果我们发现，$σ_{\rm rms}^2 $似乎是内在相关的黑洞质量在整个样本。然而，这似乎是由于将子样本2包括在分析中而导致的，这在黑洞质量和光度之间引入了额外的相关性，并人为地加强了与黑洞质量的任何相关性。因此，完整样本的结果可能会产生误导。子样本1的结果表明，$σ_{\rm rms}^2 $与X射线光度之间的相关可能是内在的，因此$σ_{\rm rms}^2 $与黑洞质量之间的反相关是可疑的。

英文摘要：

Aims. Both the black hole mass and the X-ray luminosity of AGNs have been found to be anti-correlated with the normalized excess variance ($σ_{\rm rms}^2 $) of the X-ray light curves. We investigate which correlation with $σ_{\rm rms}^2 $ is the intrinsic one. Methods. We divide a full sample of 33 AGNs (O' Neill et al. 2005) into two sub-samples. The black hole masses of 17 objects in sub-sample 1 were determined by the reverberation mapping or the stellar velocity dispersion. The black hole masses of the remaining 16 objects were estimated from the relationship between broad line region radius and optical luminosity (sub-sample 2). Then partial correlation analysis, ordinary least squares regression and K-S tests are performed on the full sample and the sub-samples, respectively. Results. We find that $σ_{\rm rms}^2 $ seems to be intrinsically correlated with the black hole mass in the full sample. However, this seems to be caused by including the sub-sample 2 into the analysis, which introduces an extra correlation between the black hole mass and the luminosity and strengthens any correlation with the black hole mass artificially. Therefore, the results from the full sample may be misleading. The results from the sub-sample 1 show that the correlation between $σ_{\rm rms}^2 $ and the X-ray luminosity may be the intrinsic one and therefore the anti-correlation between $σ_{\rm rms}^2 $ and the black hole mass is doubtful.

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