追踪先进行星系统（TAPAS）与HARPS-N VIII：热木星系统HD 118203中的宽轨道行星伴体
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N VIII. A wide-orbit planetary companion in the hot-Jupiter system HD 118203
AI总结：
本研究基于17年径向速度与TESS光度数据，确认HD 118203系统中存在一颗11倍木星质量的宽轨道伴星，形成层级行星系统，并探讨其动力学与形成机制。
摘要：
恒星HD 118203，被分类为K0亚巨星，已知拥有一颗在6.1天偏心轨道上凌日的热木星。先前的研究还揭示了径向速度（RV）域中的线性趋势，表明存在一个宽轨道上的伴体。这种层级轨道结构可能有助于研究热木星的起源。我们利用9.2米霍比-埃伯利望远镜和3.6米伽利略国家望远镜，在17年间获取了精确的径向速度测量。将这些观测与来自凌日系外行星巡天卫星（TESS）的太空光度时间序列相结合，我们构建了该系统的双行星模型。来自Hipparcos和Gaia的天体测量观测被用来约束宽轨道伴体的轨道倾角及其质量。数值模拟被用来研究系统的动力学。对光度数据进行了搜索，以寻找额外的凌日状通量下降。我们发现，额外的伴体是一颗质量为11倍木星质量的行星，围绕HD 118203运行在14年的中等偏心轨道上，与热木星构成了一个层级行星系统。发现这两颗行星在动力学上主要由于内行星的广义相对论拱点进动而解耦，使得长期相互作用边缘化。除非升交点经度差异显著，否则两颗行星的轨道可能具有相对较低的相互倾角。这种构型有利于共面高偏心迁移作为当前轨道构型的形成路径。在该系统中未发现其他半径低至2个地球半径、轨道周期小于100天的凌日行星。
英文摘要：
The star HD 118203, classified as a K0 subgiant, was known to harbour a transiting hot Jupiter planet on a 6.1-day eccentric orbit. Previous studies also revealed a linear trend in the radial velocity (RV) domain, indicative of a companion on a wide orbit. Such a hierarchical orbital architecture could be helpful in studies of the origins of hot Jupiters. We acquired precise RV measurements over 17 years using the 9.2 m Hobby-Eberly Telescope and the 3.6 m Telescopio Nazionale Galileo. Combining these observations with space-born photometric time series from the Transiting Exoplanet Survey Satellite, we constructed a two-planetary model for the system. Astrometric observations from Hipparcos and Gaia were used to constrain the orbital inclination of the wide-orbit companion and its mass. Numerical simulations were used to investigate the dynamics of the system. The photometric data were searched for additional transit-like flux drops. We found that the additional companion is an 11-Jupiter mass planet orbiting HD 118203 on a 14-year moderately eccentric orbit, constituting a hierarchical planetary system with the hot Jupiter. Both planets were found to be dynamically decoupled mainly due to the general relativistic apsidal precession of the inner planet, marginalising secular interactions. The orbits of both planets might have a relatively low mutual inclination unless the longitudes of the ascending node differ substantially. This configuration favours the coplanar high-eccentricity migration as a path to the present-day orbital configuration. No other transiting planets with radii down to 2 Earth radii and orbital periods less than 100 days were found in the system.
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