Octans年轻恒星协变的动力学回溯年龄
Dynamical traceback age of the Octans young stellar association
AI总结：
本文利用Gaia DR3天体测量与高分辨率光谱视向速度，通过多子样本、多尺度度量和多银河势模型的轨道回溯，确定Octans协变年龄约34 Myr，并指出其与Octans-Near无关。
摘要：
Octans是太阳邻域最遥远（距离d约150 pc）的年轻恒星协变之一。其年龄在现有文献中仍缺乏良好约束，需要进一步研究。我们利用Gaia空间任务第三次数据发布所提供的最先进天体测量数据，并结合由高分辨率光谱学获得的视向速度测量，计算恒星的三维位置和三维空间速度，进而推导该协变的动力学回溯年龄。我们使用不同的恒星子样本、用于定义协变尺度的不同度量，以及用于向过去积分恒星轨道的不同银河系势模型，开展了广泛的回溯分析。我们得到34^{+2}_{-2} Myr的动力学年龄，该年龄独立于恒星模型，并代表目前可获得的对Octans协变最精确的年龄估计。在对恒星视向速度进行引力红移效应校正后，我们得到33^{+3}_{-1} Myr的动力学年龄，这与我们的第一个解非常吻合。这表明，对于如此遥远的年轻恒星协变，引力红移效应很小。我们的结果也与以往研究中由锂耗竭（30–40 Myr）和等时线（20–30 Myr）获得的精度较低的年龄估计一致。通过随时间积分恒星轨道，我们表明Octans和Octans-Near的成员在过去具有不同的位置，这表明尽管二者在天空中距离很近，但这两个协变并无关联。我们的结果证实，对于约150 pc处、年龄约30 Myr的恒星团，通过回溯方法获得精确动力学年龄是可能的，并且其精度水平可与其他研究中针对距太阳50 pc以内年轻恒星群所达到的精度相同。
英文摘要：
Octans is one of the most distant ($d\sim150$pc) young stellar associations of the solar neighbourhood. Its age is still poorly constrained in the literature and requires further investigation. We take advantage of the state-of-the-art astrometry delivered by the third data release of the Gaia space mission combined with radial velocity measurements obtained from high-resolution spectroscopy to compute the 3D positions and 3D spatial velocities of the stars and derive the dynamical traceback age of the association. We performed an extensive traceback analysis using different subsamples of stars, different metrics to define the size of the association, and different models for the Galactic potential to integrate the stellar orbits in the past. We derive a dynamical age of $34^{+2}_{-2}$Myr that is independent from stellar models and represents the most precise age estimate currently available for the Octans association. After correcting the radial velocity of the stars for the effect of gravitational redshift, we obtain a dynamical age of $33^{+3}_{-1}$Myr, which is in very good agreement with our first solution. This shows that the effect of gravitational redshift is small for such a distant young stellar association. Our result is also consistent with the less accurate age estimates obtained in previous studies from lithium depletion (30-40Myr) and isochrones (20-30Myr). By integrating the stellar orbits in time, we show that the members of Octans and Octans-Near had different locations in the past, which indicates that the two associations are unrelated despite the close proximity in the sky. Our results confirm that it is possible to derive precise dynamical ages via the traceback method for $\sim30$Myr old stellar clusters at about $\sim150$pc with the same precision level that has been achieved in other studies for young stellar groups within 50pc of the Sun.
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