论文标题
恒星活动的准周期高斯过程：从物理到内核参数
Quasi-periodic Gaussian Processes for stellar activity: from physical to kernel parameters
论文作者
论文摘要
近年来，高斯流程（GP）回归已被广泛用于分析恒星和系外系列数据集。对于斑点的恒星，最流行的GP协方差函数是准周期（QP）内核，其GP的超参数在恒星和斑点的物理特性方面具有合理的解释。在本文中，我们通过使用QP GP进行模拟模拟模拟数据模拟该解释的可靠性，以及最近提出的Quasi-periodic Plus余弦（QPC）GP，将GP超参数的后验分布与点模型的输入参数进行了比较。我们发现输入恒星旋转期与QP和QPC GP时期之间的一致性很高，以及斑点衰减时间尺度与平方指数项的长度尺度之间的很好的一致性。我们还比较了给定恒星的光和径向速度（RV）曲线的超参数，发现周期和演化时间尺度非常吻合。但是，GP的谐波复杂性虽然与我们的模拟中的点属性没有明显的相关性，但在系统上对RV的谐波相关性远高于光曲线数据。最后，对于QP内核，我们研究了RVS的噪声和时间采样对超参数的影响。我们的结果表明，旋转周期和点演变时间尺度的良好覆盖范围比点的总数更重要，噪声特性决定了谐波复杂性。
In recent years, Gaussian Process (GP) regression has become widely used to analyse stellar and exoplanet time-series data sets. For spotted stars, the most popular GP covariance function is the quasi-periodic (QP) kernel, whose the hyperparameters of the GP have a plausible interpretation in terms of physical properties of the star and spots. In this paper, we test the reliability of this interpretation by modelling data simulated using a spot model using a QP GP, and the recently proposed quasi-periodic plus cosine (QPC) GP, comparing the posterior distributions of the GP hyperparameters to the input parameters of the spot model. We find excellent agreement between the input stellar rotation period and the QP and QPC GP period, and very good agreement between the spot decay timescale and the length scale of the squared exponential term. We also compare the hyperparameters derived from light and radial velocity (RV) curves for a given star, finding that the period and evolution timescales are in good agreement. However, the harmonic complexity of the GP, while displaying no clear correlation with the spot properties in our simulations, is systematically higher for the RV than for the light curve data. Finally, for the QP kernel, we investigate the impact of noise and time-sampling on the hyperparameters in the case of RVs. Our results indicate that good coverage of rotation period and spot evolution time-scales is more important than the total number of points, and noise characteristics govern the harmonic complexity.
