标题： 由APOGEE观测的开普勒、K2和TESS中M型矮星行星宿主恒星的金属量：与系外行星半径和轨道周期的趋势 显示英文标题

标题： Metallicities of M Dwarf Planet Host Stars from Kepler, K2, and TESS observed by APOGEE: Trends with Exoplanetary Radii and Orbital Periods

摘要： 研究系外行星种群的一个重要特性是宿主恒星金属量([M/H])。在本研究中，我们利用SDSS APOGEE调查的近红外高分辨率光谱和LTE计算的合成光谱，推导出45颗M型矮星（包含65颗系外行星）的恒星金属量和氧丰度。我们还研究了246颗围绕188颗M型矮星运行的系外行星的半径分布。获得的[M/H]与[O/M]分布表明，我们的样本主要由薄盘恒星组成，它们遵循银河系薄盘低-alpha序列的行为。发现半径小于3R$_{\oplus}$的小行星围绕金属量范围为(-0.6$<$[M/H]$<$+0.3)的恒星运行，而样本中的大行星仅围绕[M/H]$>=0.0$的恒星运行。这些结果表明，虽然小行星可以在不同环境中形成，但大行星更倾向于在金属丰富的原行星盘中形成。轨道周期P$_{\rm orb}<$4.3天的系外行星平均而言围绕比轨道周期更长的行星金属量更高的恒星。这个阈值小于FGK恒星（8-10天）发现的阈值，可能与M型矮星具有较小的尘埃蒸发半径有关。半径R$_{\rm p}>$4R$_{\oplus}$的系外行星的分布显示在轨道周期2到5天之间有集中现象，这可能是向内轨道迁移的结果。单次检测到的系外行星和多行星系统中的行星之间也表现出不同的行为，后者平均围绕金属量更低的恒星运行，且轨道周期大致不超过3天。 显示英文摘要

摘要： One important property in studying the exoplanet population is the host star metallicity ([M/H]). In this study, we derived stellar metallicities and oxygen abundances for 45 M dwarf stars (with 65 exoplanets) using the near-infrared high-resolution spectra from the SDSS APOGEE survey and synthetic spectra computed in LTE. We also investigated the exoplanetary radii distribution for a larger sample of 246 exoplanets orbiting 188 M dwarf stars. The [M/H] versus [O/M] distribution obtained indicates that our sample is composed mainly of thin disk stars, which follow the behavior of the low-alpha sequence in the Milky Way thin disk. Small planets with radii smaller than 3R$_{\oplus}$ were found around stars with a range of metallicities (-0.6$<$[M/H]$<$+0.3), while larger planets of the sample orbit only stars with [M/H]$>=0.0$. These results indicate that while small planets can form in different environments, larger planets preferentially form in metal-rich protoplanetary disks. Exoplanets with P$_{\rm orb}<$4.3 days orbit on average more metal-rich stars than planets with longer periods. This threshold is smaller than that found for FGK stars (8--10 days) and might be related to M dwarfs having a smaller dust sublimation radius. The distribution of exoplanets with R$_{\rm p}>$4R$_{\oplus}$ shows a concentration at orbital periods between 2 and 5 days, which may result from inward orbital migration. There is also a different behavior between single-detected exoplanets and planets from multiplanetary systems, with the latter being found on average around more metal-poor stars, and with orbital periods roughly up to 3 days.