论文标题

通过使用变更点检测技术来考虑径向速度数据中出色的活动信号

Accounting for stellar activity signals in radial-velocity data by using Change Point Detection techniques

论文作者

Simola, U., Bonfanti, A., Dumusque, X., Cisewski-Kehe, J., Kaski, S., Corander, J.

论文摘要

恒星光球上的活跃区域一直是使用径向速度(RV)方法检测类似地球外球星的主要障碍。解决恒星活动的一种通常使用的解决方案是假设RV观测值与整个时间序列的活动指标之间存在线性关系,然后从RV数据的变化(整体校正方法)中删除活动的估计贡献。但是,由于随着时间的流逝,活动区域会在光球上演变,因此RV观测和活动指标之间的相关性将相应地是各向异性的。我们提出了一种方法,该方法识别RV位置,其中RV与活动指标之间的相关性显着变化,以便更好地说明由恒星活动引起的RV的变化。所提出的方法使用统计断点方法的一般家族,通常称为变更点检测(CPD)算法; R和Python中有几种实现。在基于断点的方法和整体校正方法之间进行了详尽的比较。为了确保广泛的代表性,我们使用具有不同水平的恒星活动并且其光谱具有不同信噪比的实际恒星的测量值。当将恒星活性​​的校正分别应用于通过断点方法识别的每个时间段时,RV时间序列中的相应残差通常比通过整体校正方法获得的残差小得多。因此,广义的伦敦量表周期图包含由活性区域引起的较小峰。当专注于具有长时间序列的活性恒星时,CPD算法特别有效,例如Alpha CenB。

Active regions on the photosphere of a star have been the major obstacle for detecting Earth-like exoplanets using the radial velocity (RV) method. A commonly employed solution for addressing stellar activity is to assume a linear relationship between the RV observations and the activity indicators along the entire time series, and then remove the estimated contribution of activity from the variation in RV data (overall correction method). However, since active regions evolve on the photosphere over time, correlations between the RV observations and the activity indicators will correspondingly be anisotropic. We present an approach that recognizes the RV locations where the correlations between the RV and the activity indicators significantly change in order to better account for variations in RV caused by stellar activity. The proposed approach uses a general family of statistical breakpoint methods, often referred to as change point detection (CPD) algorithms; several implementations of which are available in R and python. A thorough comparison is made between the breakpoint-based approach and the overall correction method. To ensure wide representativity, we use measurements from real stars that have different levels of stellar activity and whose spectra have different signal-to-noise ratios. When the corrections for stellar activity are applied separately to each temporal segment identified by the breakpoint method, the corresponding residuals in the RV time series are typically much smaller than those obtained by the overall correction method. Consequently, the generalized Lomb-Scargle periodogram contains a smaller number of peaks caused by active regions. The CPD algorithm is particularly effective when focusing on active stars with long time series, such as alpha Cen B.

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