AI 中文总结
研究利用星团NGC-752填补10亿至25亿年年龄区间的陀螺年代学空白，绘制其G/K矮星自转序列，发现现有模型因缺乏中间年龄校准高估恒星年龄20%-50%，为大规模陀螺年代学提供关键锚点。
AI 中文摘要
经验陀螺年代学依赖同恒星星协将恒星自转作为质量和年龄的函数进行映射，因此其年龄预测的准确性受限于基准自转序列的数量和质量。特征明确的星团NGC-6811（年龄约10亿年）和NGC-6819（年龄约25亿年）构成了一个中间年龄区间的边界，该区间内的恒星自旋下降因缺乏可用的自转数据而受到的约束不足。在年龄约13亿年时，NGC-752是填补这一空白的关键基准，但此前的测量无法定义校准所需的G型和K型矮星自转序列。本文将基于盖亚（Gaia）的NGC-752成员列表与文献中的自转周期相结合，首次绘制出NGC-752的慢自转序列，该序列位于NGC-6811和NGC-6819的序列之间。有效温度约4500K的恒星自转速度比NGC-6811中的同类恒星更慢，这表明在约10亿年时经历自旋停滞的恒星，到NGC-752的年龄时已恢复明显的自旋下降。采用NGC-752的年龄为13亿年，我们进一步发现，现有的经验陀螺年代学模型因缺乏中间年龄的校准数据，会将许多G型和早K型矮星的年龄高估20%至50%，尽管NGC-752绝对年龄的不确定性可能解释部分偏差。因此，NGC-752为提高自转年龄估计提供了必要的锚点，这一校准恰逢其时，因为盖亚DR4、罗曼空间望远镜（Roman）和柏拉图（PLATO）预计将为数千万颗恒星提供自转周期，使基准序列的年龄覆盖范围成为大规模陀螺年代学的主要限制因素。
英文摘要
Empirical gyrochronology relies on co-eval stellar associations to map stellar rotation as a function of mass and age. The accuracy of its age predictions is therefore limited by the number and quality of benchmark rotation sequences. The well-characterized clusters NGC-6811 (t ~ 1 Gyr) and NGC-6819 (t ~ 2.5 Gyr) bracket an intermediate-age interval in which stellar spin-down remains poorly constrained due to lack of available rotation data. At t ~ 1.3 Gyr, NGC-752 provides a critical benchmark within this gap, but previous measurements could not define the G- and K-dwarf rotation sequence needed for calibration. Here, we combine Gaia-based NGC-752 membership lists with literature rotation periods to map NGC-752's slow-rotator sequence for the first time. We identify a well-defined sequence intermediate between those of NGC-6811 and NGC-6819. Stars near Teff ~ 4500 K rotate more slowly than their counterparts in NGC-6811, indicating that stars experiencing stalled spin-down at ~1 Gyr have resumed appreciable spin-down by the age of NGC-752. Adopting an age of 1.3 Gyr for NGC-752, we further show that existing empirical gyrochronology models overestimate the ages of many G and early-K dwarfs by 20--50% because they lack intermediate-age calibration data, although uncertainty in the absolute age of NGC-752 may account for part of this offset. NGC-752 therefore provides a necessary anchor for improving rotational age estimates. This calibration is especially timely because Gaia DR4, Roman, and PLATO are expected to yield rotation periods for tens of millions of stars, making the age coverage of benchmark sequences a principal limitation on large-scale gyrochronology.
CommentsAccepted to ApJ Letters
