Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e. metallicity, a stellar parameter which strongly influences the occurrence of gas giant planets. We obtained infrared spectra of 121 M dwarfs stars monitored by the California Planet Search (CPS) and determined metallicities with an accuracy of 0.08 dex. The mean and standard deviation of the sample is -0.05 and 0.20 dex, respectively. We parameterized the metallicity dependence of the occurrence of giant planets on orbits with period less than 2 yr around solar-type stars and applied this to our M dwarf sample to estimate the expected number of giant planets. The number of detected planets (3) is lower than the predicted number (6.4) but the difference is not very significant (12% probability of finding as many or fewer planets). The three M dwarf planet hosts are not especially metal rich and the most likely value of the power-law index relating planet occurrence to metallicity is 1.06 dex per dex for M dwarfs compared to 1.80 for solar-type stars; this difference, however, is comparable to uncertainties. Giant planet occurrence around both types of stars allows, but does not necessarily require, mass dependence of $\sim 1$ dex per dex. The actual planet-mass-metallicity relation may be complex and elucidating it will require larger surveys like those to be conducted by ground-based infrared spectrographs and the Gaia space astrometry mission.
Uniform Metallicity Measurements of M Dwarf Planet Hosts Support Metallicity-Dependent Sub-Neptune Formation
McMaster University（麦克马斯特大学）；University of California, Berkeley（加州大学伯克利分校）；California Institute of Technology（加州理工学院）；San Francisco State University（旧金山州立大学）；Georgia State University（佐治亚州立大学）；RECONS Institute（RECONS研究所）；Flatiron Institute（平顿研究所）
The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars
陀螺年代学的方法将恒星的年龄与自转周期联系起来。然而，最近的证据偏离gyrochronology关系的文献报道。在这里，我们研究恒星和它的伴星之间的潮汐相互作用对恒星自转速度的影响，以解释奇特的恒星自转速度。一颗恒星和它的行星的相互作用是使用一个全面的数值框架，结合潮汐摩擦，磁制动，行星迁移，和详细的恒星演化模型从GARSTEC网格。我们专注于近距离的同伴从1至20 M $_{Jup}$轨道低质量，0.8和1 M $_{\odot}$，主序星具有广泛的金属量范围从[Fe/H] = -1太阳。我们的模拟表明，恒星与其伴星之间的动力学相互作用可能会产生不同的结果，这取决于初始半长轴和行星的质量，以及其宿主恒星的质量和金属丰度。在大多数情况下，特别是在行星被吞没的情况下，我们发现恒星的自转速度从1公里$^{-1}$增加到40公里以上$^{-1}$，而恒星仍然在主序星上。我们的模型的主要预测是，低质量的主序恒星与异常的旋转速度应该是更常见的低金属丰度，因为较低的[Fe/H]有利于更快的行星吞没，在大质量行星的发生率接近是在所有的金属丰度相似。我们的方案解释了特殊的旋转速度的低质量主序星的恒星和它的同伴之间的潮汐相互作用。目前的观测样本太小且不完整，因此不允许我们测试我们的模型。
Chemical abundances and kinematics of 257 G-, K-type field giants. Setting a base for further analysis of giant-planet properties orbiting evolved stars
Gaia Exoplanet Orbits, Demographics, and Evolution Survey (GEODES): Characteristics of Three Long-Period Companions Accelerating their Host Stars
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；University of California Los Angeles（加州大学洛杉矶分校）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；Princeton University（普林斯顿大学）
