Activity induced variation in spin-orbit angles as derived from Rossiter–McLaughlin measurements
Activity induced variation in spin-orbit angles as derived from Rossiter–McLaughlin measurements
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DOI：
10.1051/0004-6361/201833709
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发表时间：
2018-09
影响因子：
6.5
通讯作者：
M. Oshagh;A. Triaud;A. Burdanov;P. Figueira;A. Reiners;Nuno C. Santos;J. Faria;G. Boué;R. Díaz;S. Dreizler;S. Boldt;L. Delrez;E. Ducrot;M. Gillon;A. G. Mesa;E. Jehin;S. Khalafinejad;S. Kohl;L. Serrano;S. Udry
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作者：
M. Oshagh;A. Triaud;A. Burdanov;P. Figueira;A. Reiners;Nuno C. Santos;J. Faria;G. Boué;R. Díaz;S. Dreizler;S. Boldt;L. Delrez;E. Ducrot;M. Gillon;A. G. Mesa;E. Jehin;S. Khalafinejad;S. Kohl;L. Serrano;S. Udry
用于估计系外行星系统的天空投影自旋轨道角的最强大方法之一是通过称为罗西特麦克劳林（RM）效应的光谱凌日观测。到目前为止，大多数单次 RM 观测都被用来估计自旋轨道角，因此还没有关于估计的自旋轨道角随凌日变化的变化的研究。恒星活动可以改变光度凌日光曲线的形状，并且以类似的方式可以使 RM 信号变形。在本文中，我们提出了使用 HARPS 摄谱仪获得的几个已知凌日行星的 RM 观测结果，这些行星都凌日极其活跃的恒星，并通过单独分析它们，我们评估了估计的自旋轨道角的变化。我们的结果表明，由于不同夜晚恒星活动区域结构的变化，估计的自旋轨道角在不同的凌日期间可能会有很大差异（高达~42°）。这一发现几乎比模拟预测的预期变化大两倍。我们无法识别估计的自旋轨道角的变化与恒星磁活动指标之间的任何有意义的相关性。我们还研究了两种可能的方法来减轻恒星活动对 RM 观测的影响。第一个策略是基于获得多个 RM 观测结果并将它们折叠起来以减少恒星活动噪声。我们的结果表明，这是解决这个问题的可行且可靠的方法。第二种方法是基于使用 TRAPPIST/SPECULOOS 望远镜同时获取高精度短节奏光度凌日光曲线，它提供了有关恒星活动区域属性的更多信息，并允许更好的 RM 建模。
One of the most powerful methods used to estimate sky-projected spin-orbit angles of exoplanetary systems is through a spectroscopic transit observation known as the RossiterMcLaughlin (RM) effect. So far mostly single RM observations have been used to estimate the spin-orbit angle, and thus there have been no studies regarding the variation of estimated spin-orbit angle from transit to transit. Stellar activity can alter the shape of photometric transit light curves and in a similar way they can deform the RM signal. In this paper we present several RM observations, obtained using the HARPS spectrograph, of known transiting planets that all transit extremely active stars, and by analyzing them individually we assess the variation in the estimated spin-orbit angle. Our results reveal that the estimated spin-orbit angle can vary significantly (up to ~42°) from transit to transit, due to variation in the configuration of stellar active regions over different nights. This finding is almost two times larger than the expected variation predicted from simulations. We could not identify any meaningful correlation between the variation of estimated spin-orbit angles and the stellar magnetic activity indicators. We also investigated two possible approaches to mitigate the stellar activity influence on RM observations. The first strategy was based on obtaining several RM observations and folding them to reduce the stellar activity noise. Our results demonstrated that this is a feasible and robust way to overcome this issue. The second approach is based on acquiring simultaneous high-precision short-cadence photometric transit light curves using TRAPPIST/SPECULOOS telescopes, which provide more information about the stellar active region’s properties and allow a better RM modeling.