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arXiv 1202.3783astro-ph.CO
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类星体光变是阻尼随机游动吗？

Is Quasar Optical Variability a Damped Random Walk?

Ying Zu, C. S. Kochanek, Szymon Kozłowski, Andrzej Udalski

备注：
6 pages, 6 figures, ApJ Accepted. For a brief video explaining the key result of this paper, see http://www.youtube.com/watch?v=8_UzzHuLczw, or http://v.youku.com/v_show/id_XMzUzMDAwMTQ0.html in countries where YouTube is not accessible
发表信息：
2013 ApJ 765 106
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摘要：

阻尼随机游走（DRW）模型越来越多地用于模拟类星体光学光变曲线的变化，但DRW模型是否能在所有时间尺度上充分描述类星体的光学变化仍不确定。使用OGLE类星体光变曲线的样本，我们认为四个修改DRW模型引入额外的参数到协方差函数搜索偏离DRW模型的短期和长期的时间尺度。我们发现DRW模型在时间尺度上具有良好的一致性，这些时间尺度被数据很好地采样（从一个月到几年），可能在额外的参数中具有一些内在的分散性，但这一结论取决于所采用的统计检验，并且对光度误差的估计是否正确在~ 10%以内敏感。在非常短的时间尺度上（几个月以下），我们看到一些证据表明存在一个截止点，低于该截止点的相关性比DRW模型更强，这与Mushotzky等人（2011）使用开普勒的类星体光变曲线的最新发现相呼应。在很长的时间尺度上（>几年），光变曲线不能很好地约束模型，但与DRW模型一致。

英文摘要：

The damped random walk (DRW) model is increasingly used to model the variability in quasar optical light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar optical variability across all time scales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long time scales. We find good agreement with the DRW model on time scales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters, but this conclusion depends on the statistical test employed and is sensitive to whether the estimates of the photometric errors are correct to within ~10%. On very short time scales (below a few months), we see some evidence of the existence of a cutoff below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. (2011) using quasar light curves from Kepler. On very long time scales (> a few years), the light curves do not constrain models well, but are consistent with the DRW model.

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