Chemo-kinematic Ages of Eccentric-planet-hosting M Dwarf Stars
Chemo-kinematic Ages of Eccentric-planet-hosting M Dwarf Stars
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DOI：
10.3847/1538-4357/aad40e
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发表时间：
2018-07
期刊：
影响因子：
--
通讯作者：
M. Veyette;P. Muirhead
中科院分区：
文献类型：
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作者：
M. Veyette;P. Muirhead
M型矮星是令人兴奋的系外行星研究目标;然而，它们的基本恒星性质很难测量。也许最具挑战性的属性是恒星年龄。一旦进入主序列，M矮星的温度和亮度就会发生微妙的变化，这就需要新颖的统计技术来估计它们的年龄。在本文中，我们使用运动学和α元素富集的组合来推断已知的偏心行星托管M矮星的年龄，两者都与类太阳FGK恒星的年龄相关。我们校准我们的方法FGK星在贝叶斯上下文中。为了测量α-富集，我们使用来自CARMENES系外行星巡天的公开光谱和最近开发的利用Y波段中的单个Ti i和Fe i吸收线的[Ti/Fe]校准。潮汐效应预计会在短时间尺度上使短周期行星的轨道圆化;然而，我们发现了一些轻微偏心的近距离行星绕着古老的（108 Gyr）恒星运行。对于这些系统，我们使用我们的年龄来约束行星的潮汐耗散参数Qp。对于两颗小型海王星行星，GJ 176 B和GJ 536 B，我们发现它们的Qp值更接近于冰巨星，而不是太阳系中的类地行星。对于GJ 436 B，我们估计的年龄和约束的Qp是>105，在很好的协议，从其推断的潮汐加热的约束。我们发现GJ 876 d在其一生中可能经历了重大的轨道演化，可能受到其三个外伴星的影响，这些伴星的轨道处于拉普拉斯共振状态。
The M dwarf stars are exciting targets for exoplanet investigations; however, their fundamental stellar properties are difficult to measure. Perhaps the most challenging property is stellar age. Once on the main sequence, M dwarfs change imperceptibly in their temperature and luminosity, necessitating novel statistical techniques for estimating their ages. In this paper, we infer ages for known eccentric-planet-hosting M dwarfs using a combination of kinematics and α-element enrichment, both shown to correlate with age for Sun-like FGK stars. We calibrate our method on FGK stars in a Bayesian context. To measure α-enrichment, we use publicly available spectra from the CARMENES exoplanet survey and a recently developed [Ti/Fe] calibration utilizing individual Ti i and Fe i absorption lines in the Y band. Tidal effects are expected to circularize the orbits of short-period planets on short timescales; however, we find a number of mildly eccentric, close-in planets orbiting old (∼8 Gyr) stars. For these systems, we use our ages to constrain the tidal dissipation parameter of the planets, Qp. For two mini-Neptune planets, GJ 176 b and GJ 536 b, we find that they have Qp values more similar to the ice giants than to the terrestrial planets in our solar system. For GJ 436 b, we estimate an age of and constrain the Qp to be >105, in good agreement with constraints from its inferred tidal heating. We find that GJ 876 d has likely undergone significant orbital evolution over its lifetime, potentially influenced by its three outer companions that orbit in a Laplace resonance.