Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf
Two planets around Kapteyn's star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf
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围绕卡普坦恒星的两颗行星：一颗寒冷的超级地球和一颗围绕最近的光晕红矮星运行的温带超级地球
DOI：
10.1093/mnrasl/slu076
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发表时间：
2014
影响因子：
4.8
通讯作者：
Arriagada
中科院分区：
文献类型：
--
作者：
Anglada-Escudé;Arriagada
现在可以使用多普勒光谱学在附近的低质量恒星周围探测到几个地球质量的系外行星。在这封信中，我们调查的径向速度变化的Kapteyn的星星，这是一个亚矮星M-星星和最近的晕对象到太阳。观测包括档案和新的HARPS（高精度径向速度行星搜索器），高分辨率阶梯光谱仪（HIRES）和行星射电光谱仪（PFS）多普勒测量。两个多普勒信号被检测到在48和120天的周期使用似然周期图和贝叶斯分析的数据。使用同样的技术，活动指数和档案全天自动巡天光度测定显示了数百天量级的低层活动周期性的证据。然而，在相同的时间尺度上，径向速度的变化没有显着的相关性。在模型中包含行星开普勒信号导致相关和过量白色噪声的水平与年轻的G，K和M矮星相比显着降低。我们的结论是，卡普坦的星星最有可能是由两个超级地球质量的行星，其中一个是在其环绕恒星的宜居带轨道，成为迄今为止已知的最古老的潜在的宜居行星。鉴于卡普坦星星的特殊起源和运动历史，行星系统的存在和长期生存似乎是一个了不起的壮举。在晕星周围探测到超级地球质量的行星，为研究银河系早期的行星形成过程提供了重要的信息。
Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this Letter, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS (High Accuracy Radial velocity Planet Searcher), High Resolution Echelle Spectrometer (HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 d using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival All Sky Automated Survey (ASAS-3) photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seem a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.