约35 Myr '蛇'疏散星团中锂凹陷的出现
Emergence of a lithium dip in ~35 Myr "Snake" Open Clusters
AI总结：
研究发现约35 Myr的'蛇'疏散星团中存在锂凹陷，挑战传统观点，并揭示旋转速度与锂耗尽的关联。
摘要：
我们报告了在恒星'蛇'（年龄=35±5 Myr）中发现锂凹陷（Li-dip），这挑战了传统观点，即锂凹陷仅在年龄大于等于150 Myr时出现。利用GALAH DR4（R≈28,000）的高分辨率光谱数据，对211颗成员恒星进行分析，我们发现6200-6800 K温度范围内存在明显的锂 depletion 特征，深度约为ΔA(Li)≈0.40 dex。我们的分析揭示了两个关键进展：锂凹陷出现的时间比之前的观测早约100 Myr，且在凹陷温度范围内，发现旋转速度与锂耗尽之间存在显著相关性。具体而言，快速旋转者（v sin i >25 km s⁻¹）比慢速旋转者（v sin i <25 km s⁻¹）表现出更强的锂耗尽。这种趋势表明，快速旋转者在对流-辐射边界发展出更强的旋转剪切，增强了湍流混合并加速了锂的破坏。还发现年轻疏散星团中锂平台的低温边缘可以低至5500 K。
英文摘要：
We report the discovery of a lithium dip (Li-dip) in the stellar "Snake" (age = $35 \pm 5$ Myr), challenging the classical view that Li-dips emerge only at ages $\gtrsim 150$ Myr. Using high-resolution spectra from GALAH DR4 ($R \sim 28,000$) for 211 member stars, we identify a clear depletion feature in a $T_{\mathrm{eff}}$ range of 6200--6800 K with a depth of $ΔA(\mathrm{Li}) \approx 0.40$ dex. Our analysis reveals two key advances: the Li-dip appears $\gtrsim 100$ Myr earlier than the previous observations, and within the dip temperature range, a significant correlation is found between rotational velocity and lithium depletion. Specifically, fast rotators ($v \sin i > 25$ km s$^{-1}$) exhibit stronger lithium depletion than slow rotators ($v \sin i < 25$ km s$^{-1}$). This trend suggests that faster rotators develop stronger rotational shear at the convective-radiative boundary, which enhances turbulent mixing and accelerates lithium destruction. It is also found that the lower temperature edge of the lithium plateau can reach as low as 5500 K for the young open clusters.
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