模拟HD200466行星系统的一个强活动周期
A vigorous activity cycle mimicking a planetary system in HD200466
摘要：
恒星活动可能是径向速度（RV）噪声的来源，并可以重现类似于系外行星产生的周期性RV变化。我们介绍了视觉双星HD 200466的活跃活动周期，这是一个由两颗几乎相同的太阳型恒星组成的系统，在距离44+/-2 pc处的视间距为4.6角秒。十多年来的高精度RV、自适应光学（AO）图像和丰度均已获得。在RV的线性趋势被发现的中学。我们认为这是由于双星轨道的原因，一旦与天体测量数据相结合，它就强烈地限制了双星在高偏心率（e~0.85）和~21 AU的相当小的近星点处的轨道解。如果从主视向速度曲线中减去这个轨道运动，得到一个约为1300 d的显著周期（误报概率<0.1%），这在第一次分析中表明存在一颗巨行星，但它被证明是由于恒星活动周期。由于我们的光谱不包括Ca~II共振线，我们测量了一个基于H α线的色球活动指示器，以研究活动周期和长期活动变化之间的相关性。虽然线轮廓的平分线分析没有显示出活动的明确指示，但H α线指示器和RV测量值之间的相关性识别出存在强活动周期。
英文摘要：
Stellar activity can be a source of radial velocity (RV) noise and can reproduce periodic RV variations similar to those produced by an exoplanet. We present the vigorous activity cycle in the primary of the visual binary HD200466, a system made of two almost identical solar-type stars with an apparent separation of 4.6 arcsec at a distance of 44+/-2 pc. High precision RV over more than a decade, adaptive optics (AO) images, and abundances have been obtained for both components. A linear trend in the RV is found for the secondary. We assumed that it is due to the binary orbit and once coupled with the astrometric data, it strongly constrains the orbital solution of the binary at high eccentricities (e~0.85) and quite small periastron of ~21 AU. If this orbital motion is subtracted from the primary radial velocity curve, a highly significant (false alarm probability <0.1%) period of about 1300 d is obtained, suggesting in a first analysis the presence of a giant planet, but it turned out to be due to the stellar activity cycle. Since our spectra do not include the Ca~II resonance lines, we measured a chromospheric activity indicator based on the Halpha line to study the correlation between activity cycles and long-term activity variations. While the bisector analysis of the line profile does not show a clear indication of activity, the correlation between the Halpha line indicator and the RV measurements identify the presence of a strong activity cycle.
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