A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone
A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone
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DOI：
10.1051/0004-6361/201321331
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发表时间：
2013-08-01
影响因子：
6.5
通讯作者：
Jones, Hugh R. A.
中科院分区：
文献类型：
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作者：
Anglada-Escude, Guillem;Tuomi, Mikko;Jones, Hugh R. A.
上下文由于低质量恒星的光度较低，液态水可以存在于地球大小的行星上的轨道相对较近，这会产生多普勒信号，使用最先进的多普勒光谱仪可以检测到。GJ 667 C已经被两个超级地球候选者环绕。我们最近应用开发的数据分析方法来调查数据是否支持存在额外的companions. Methods。我们从HARPS提取的光谱中获得新的多普勒测量，并将它们与PFS和HIRES光谱仪中获得的测量结果相结合。我们使用贝叶斯和基于周期图的方法来重新评估候选人的数量，并评估每个检测的置信度。在其他测试中，我们通过分析每个多普勒信号与几个活动指数测量值的相关性来验证行星候选者，并研究信号的可能准周期性质。GJ 667 C的多普勒测量可以用六个更好的描述。（甚至七个）开普勒类信号：两个已知的候选者（B和c）;另外三个少数地球质量的候选者，周期为92天，62天和39天（d、e和f）;一个寒冷的超级地球在260天的轨道（g）和诱人的证据，一个类似的1米圈以上的物体在近距离轨道17天（h）。我们探索长期稳定的轨道是否与数据兼容，通过整合来自贝叶斯采样的8 × 10（4）的解决方案。我们使用长期频率分析来评估它们的稳定性。由六颗行星组成的系统与动态稳定配置兼容。至于太阳系，最稳定的解决方案不包含平均运动共振，并通过解析拉普拉斯-拉格朗日解决方案很好地描述。初步分析还表明，行星的质量不可能高于多普勒测量获得的最小质量的两倍。第七颗行星（h）的存在是由以下事实支持的：它似乎正中心位于六行星解决方案中唯一剩下的稳定岛屿上。考虑到恒星通量和潮汐耗散效应的适居性评估表明，有三颗（也许是四颗）行星可能适合居住。多普勒和天基凌日观测表明：1）超级地球的动力系统相对丰富，2）M矮星比早期类型的恒星有更多的小行星。这两个趋势共同表明，GJ 667 C是新兴的M星群体中的第一批成员之一，在其可居住区中有多个低质量行星。
Context. Since low-mass stars have low luminosities, orbits at which liquid water can exist on Earth-sized planets are relatively close-in, which produces Doppler signals that are detectable using state-of-the-art Doppler spectroscopy.Aims. GJ 667C is already known to be orbited by two super-Earth candidates. We have recently applied developed data analysis methods to investigate whether the data supports the presence of additional companions.Methods. We obtain new Doppler measurements from HARPS extracted spectra and combined them with those obtained from the PFS and HIRES spectrographs. We used Bayesian and periodogram-based methods to re-assess the number of candidates and evaluated the confidence of each detection. Among other tests, we validated the planet candidates by analyzing correlations of each Doppler signal with measurements of several activity indices and investigated the possible quasi-periodic nature of signals.Results. Doppler measurements of GJ 667C are described better by six (even seven) Keplerian-like signals: the two known candidates (b and c); three additional few-Earth mass candidates with periods of 92, 62, and 39 days (d, e and f); a cold super-Earth in a 260-day orbit (g) and tantalizing evidence of a similar to 1 M-circle plus object in a close-in orbit of 17 days (h). We explore whether long-term stable orbits are compatible with the data by integrating 8 x 10(4) solutions derived from the Bayesian samplings. We assess their stability using secular frequency analysis.Conclusions. The system consisting of six planets is compatible with dynamically stable configurations. As for the solar system, the most stable solutions do not contain mean-motion resonances and are described well by analytic Laplace-Lagrange solutions. Preliminary analysis also indicates that masses of the planets cannot be higher than twice the minimum masses obtained from Doppler measurements. The presence of a seventh planet (h) is supported by the fact that it appears squarely centered on the only island of stability left in the six-planet solution. Habitability assessments accounting for the stellar flux, as well as tidal dissipation effects, indicate that three (maybe four) planets are potentially habitable. Doppler and space-based transit surveys indicate that 1) dynamically packed systems of super-Earths are relatively abundant and 2) M-dwarfs have more small planets than earlier-type stars. These two trends together suggest that GJ 667C is one of the first members of an emerging population of M-stars with multiple low-mass planets in their habitable zones.