温带亚海王星M矮星宿主恒星的年龄
Stellar Ages of M Dwarf Hosts of Temperate Sub-Neptunes
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中文总结 AI 辅助
本文利用锂吸收、自转周期和运动学方法测定六颗M矮星宿主（含TOI-270、K2-18等）的年龄，发现其年龄在2.8-8.6 Gyr（自转法），为温带亚海王星系统演化提供年龄参考。
中文摘要 AI 辅助
测量M矮星的年龄是恒星天体物理学中的一个核心挑战。这些恒星演化非常缓慢，以至于等时线拟合几乎无法提供约束，需要采用基于自转、活动和运动学的替代方法。可靠的年龄有助于约束M矮星周围行星系统的形成与演化，包括目前正利用詹姆斯·韦布空间望远镜（JWST）进行表征的温带亚海王星。我们利用6708 Å处的锂吸收线、自转周期和银河系运动学，对六颗邻近的M矮星行星宿主（TOI-732、TOI-736、TOI-270、TOI-1468、TOI-1231和K2-18）进行了年龄分析。在所有目标中，Li I 6708 Å特征均未在3σ以上被探测到，表明锂已显著耗尽，年龄超过200 Myr。39至145天的自转周期给出的年龄为2.8至8.6 Gyr，该结果基于疏散星团M矮星进行校准，并包含了自转-年龄关系的固有弥散。运动学年龄范围为0.8至13 Gyr，不确定度为4至6 Gyr。这些年龄对每颗恒星而言精度较低，但有助于识别异常值，如TOI-1231（约13 Gyr）和K2-18（约1至2 Gyr），并将这些恒星置于银河系背景中。在已测得周期的恒星中，自转给出的年龄约束比运动学紧密2至6倍；而在必须从色球活动推断周期的恒星中，两者给出的约束相当。结合多种指标能够更可靠地分类这些恒星的演化状态，为未来的比较研究提供参考点。
英文摘要
Measuring M dwarf ages is a central challenge in stellar astrophysics. These stars evolve so slowly that isochrone fitting gives little constraint, requiring alternative methods based on rotation, activity, and kinematics. Reliable ages help constrain the formation and evolution of planetary systems around M dwarfs, including the temperate sub-Neptunes now being characterised with the James Webb Space Telescope (JWST). We present an age analysis of six nearby M dwarf planet hosts (TOI-732, TOI-736, TOI-270, TOI-1468, TOI-1231, and K2-18) using lithium absorption at 6708 Å, rotation periods, and Galactic kinematics. The Li I 6708 Åfeature is absent above 3$σ$ in all targets, implying substantial depletion and ages exceeding 200 Myr. Rotation periods of 39-145 days yield ages of 2.8-8.6 Gyr, calibrated against open cluster M dwarfs and including the intrinsic dispersion of the rotation-age relation. Kinematic ages span 0.8-13 Gyr with uncertainties of 4-6 Gyr. These are less precise per star but help identify outliers such as TOI-1231 (~13 Gyr) and K2-18 ( ~1-2 Gyr) and place the stars in Galactic context. Rotation yields age constraints 2-6 times tighter than kinematics where periods are measured, and comparable constraints where periods must be inferred from chromospheric activity. Combining multiple indicators enables more secure classification of these stars' evolutionary states, providing reference points for future comparative studies.
发表机构
- Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）
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