AI 中文总结
本研究重新审视近共振多行星系统是否更年轻的论断，发现表观年轻性源于观测选择效应，而非真实年龄差异。
AI 中文摘要
近期研究声称，开普勒任务发现的拥有近共振行星对的多行星系统——尤其是那些接近二阶平均运动共振（MMRs）的系统——其恒星速度弥散度比开普勒行星宿主的总体群体更小。将速度弥散度解释为年龄指标，这些研究得出结论：近共振系统在统计上更年轻。我们重新审视这一论断，但明确考虑厚盘恒星的污染，厚盘恒星运动学温度更高，且遵循与薄盘恒星不同的年龄-速度弥散关系（AVR）。利用运动学判据区分薄盘和厚盘恒星，我们发现被归类为具有合理二阶共振对的系统，更倾向于由更明亮、距离更近的恒星所拥有，因此比总体样本受厚盘恒星的污染更少。在应用阈值移除可能的厚盘污染物（TD/D<0.1）后，近共振系统的垂直速度弥散度与开普勒多行星样本的总体垂直速度弥散度在统计上无显著差异。我们得出结论，开普勒观测到的近共振系统的表观运动学年轻性，可能并非源于真实的年龄差异，而是由与宿主恒星性质和行星可探测性相关的观测选择效应导致。我们还对超短周期行星（USPs）的运动学年龄进行了评述。
英文摘要
Recent studies have claimed that Kepler multi-planet systems hosting near-resonant planet pairs---particularly those near second-order mean-motion resonances (MMRs)---exhibit smaller stellar velocity dispersions than the general population of Kepler planet hosts. Interpreting velocity dispersion as an age indicator, these works concluded that near-resonant systems are systematically younger. We revisit this claim, but we explicitly account for contamination by thick disk stars, which are kinematically hotter and follow a different age-velocity dispersion relation (AVR) than thin disk stars. Using the kinematic criterion to separate thin and thick disk stars, we show that systems classified as having plausible second-order resonant pairs are preferentially hosted by brighter, closer stars and are therefore less contaminated by thick disk stars than the overall sample. After applying a cut to remove probable thick disk contaminants (${\rm TD/D}<0.1$), the vertical velocity dispersion of near-resonant systems becomes statistically indistinguishable from that of the overall Kepler multi-planet sample. We conclude that the apparent kinematic youth of near-resonant systems in Kepler may not be due to a genuine age difference, but rather arises from observational selection effects linked to host star properties and planet detectability. We also comment on the kinematic ages of ultra-short-period planets (USPs).
Comments7 pages, 5 figures, accepted. For a related issue, see our companion paper (Q. Hu et al.) appearing on the same day on arXiv
