活动星系核的微变：不同统计方法的研究II。模拟图像的光变曲线
Microvariability in AGNs: study of different statistical methods II. Light curves from simulated images
摘要：
在以前的文章中，我们研究了两种统计方法用于分析活动星系核（AGN）的变化：C和F统计。应用它们观察到的差分光变曲线的39 AGN，我们发现，即使C标准不能被认为是一个实际的统计检验，它仍然可以是一个有用的参数来检测可变性，而F是一个很好的检测器的非可变性。为了在受控输入条件下测试这些结果，以便可以单独评估不同的误差源，我们生成了一系列合成差分光变曲线，模拟具有不同大气条件的天文图像，例如云量，视宁度或天空亮度，以及AGN的几种类型的固有变化，所有这些都具有特定的仪器配置。在获得每种情况下的光变曲线后，我们将这两种统计量应用于它们，以测试它们的可靠性。我们发现，权重系数应始终与这些指数一起使用。F检验倾向于将有噪声的非变量曲线分类为变量（即假阳性），尽管正确分类非变量曲线是可靠和稳健的。相反，尽管C指数倾向于给出假阴性，但我们发现，每当C指数指示源是可变的时，它实际上是可变的。最后，具有低振幅变化的光变曲线更可能受到大气条件变化的影响。
英文摘要：
In a previous paper, we studied two statistical methods used to analyse the variability of active galactic nuclei (AGNs): the C and F statistics. Applying them to observed differential light-curves of 39 AGNs, we found that, even though the C criterion cannot be considered as an actual statistical test, it could still be a useful parameter to detect variability, whereas F is a good detector of non-variability. In order to test these results under controlled input conditions, so that the different error sources could be individually evaluated, we generated a series of synthetic differential light curves simulating astronomical images with different atmospheric conditions, such as cloud cover, seeing or sky brightness, as well as several types of intrinsic variability of the AGN, all with a specific instrumental configuration. Having obtained light curves for each case, we applied both statistics to them in order to test their reliability. We found that a weight factor should always be used with these indices. The F test has a tendency to classify noisy non-variable curves as variable (i.e. false positives), although it is reliable and robust to correctly classify non-variable curves. On the contrary, although the C index tends to give false negatives, we found that whenever the C index indicates a source to be variable, it effectively is. Finally, light curves with low amplitude variabilities are more likely to be affected by changes in atmospheric conditions.
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