标题： 利用高分辨率光谱搜寻32个疏散星团中的富锂巨星 显示英文标题

标题： Search for lithium-rich giants in 32 open clusters with high-resolution spectroscopy

摘要： 富锂巨星非常稀有，它们的存在挑战了我们对恒星结构和演化的理解。 我们利用通过HARPS和UVES收集的高质量样本，以寻找富锂巨星并识别导致锂丰度增加的机制。 我们为属于32个疏散星团的247颗恒星推导出恒星参数，这些恒星的年龄范围为0.07吉年到3.6吉年。我们使用光谱合成技术代码FASMA对样本中的228颗恒星进行了丰度分析。 我们还利用来自盖亚和PARSEC等时线的天文学测量和测光数据确定了恒星的年龄、距离和消光，以限制它们的演化阶段。 我们的样本覆盖了从1到超过6倍太阳质量的宽广范围的恒星质量，其中大多数恒星的质量高于2倍太阳质量。 我们发现了14颗典型的经历了第一次物质下沉的富锂巨星。 这占我们总样本的6%，比通常在场星中发现的比例要高。 除了典型的标准值外，我们还以母星的最大锂丰度作为锂富集的判据。 我们发现在八颗已经经历过第一次物质下沉且表现出强烈锂谱线的恒星中也存在锂增强现象，这是因为同一演化阶段的同族恒星具有显著不同的锂丰度。 我们确认锂含量较高的巨星与快速自转的巨星比例较高相对应，这表明锂增强与恒星自转之间存在联系，正如恒星模型所预测的那样。 我们的富锂巨星处于各种不同的演化阶段，这意味着没有单一的锂产生机制负责锂富集，而是不同内在或外在机制可能同时起作用。 显示英文摘要

摘要： Lithium-rich giant stars are rare and their existence challenges our understanding of stellar structure and evolution. We profit from the high-quality sample gathered with HARPS and UVES, in order to search for Li-rich giants and to identify the Li enrichment mechanisms responsible. We derive stellar parameters for 247 stars belonging to 32 open clusters, with 0.07 Ga < ages < 3.6 Ga. We employed the spectral synthesis technique code FASMA for the abundance analysis of 228 stars from our sample. We also determined ages, distances, and extinction using astrometry and photometry from Gaia and PARSEC isochrones to constrain their evolutionary stage. Our sample covers a wide range of stellar masses from 1 to more than 6 solar masses where the majority of the masses are above 2 solar masses. We have found 14 canonical Li-rich giant stars which have experienced the first dredge-up. This corresponds to 6% of our total sample, which is higher than what is typically found for field stars. Apart from the canonical limit, we use the maximum Li abundance of the progenitor stars as a criterion for Li enrichment. We find Li enhancement also among eight stars which have passed the first dredge up and show strong Li lines based on the fact that stars at the same evolutionary stage in the same cluster have significantly different Li abundances. We confirm that giants with higher Li abundance correspond to a higher fraction of fast-rotating giants, suggesting a connection between Li enhancement and stellar rotation as predicted by stellar models. Our Li-rich giants are found in various evolutionary stages implying that no unique Li production mechanism is responsible for Li enrichment but rather different intrinsic or external mechanisms can be simultaneously at play.