标题： 低质量恒星中锂生产的普遍发现 显示英文标题

标题： Discovery of ubiquitous lithium production in low-mass stars

摘要： 绝大多数质量与太阳相似的恒星预计只会通过低温核燃烧在其生命周期中摧毁锂。 现在，通过对数十万颗红巨星的观测已经证实了这一点（Brown等，1989；Kumar等，2011；Deepak等，2019；Singh等，2019；Casey等，2019）。 在这里，我们首次对处于演化红团阶段恒星的锂含量进行了大规模系统的调查，该阶段直接继红巨星分支阶段之后。 令人惊讶的是，我们发现所有红团恒星在其演化的阶段都具有高水平的锂。 平均而言，在红巨星分支阶段结束后，锂含量增加了40倍。 这表明所有低质量恒星在红巨星分支顶端和红团之间都会经历一个锂生产阶段。 我们证明了我们的发现并未被恒星理论所预测，揭示了观测与模型之间的明显矛盾。 我们还显示，被广泛研究的非常富锂巨星（Brown等，1989；Reddy等，2005；Kumar等，2011；Singh等，2019；Casey等，2019），其锂丰度 A(Li)$> +1.5$dex，仅代表锂增强分布的极端尾部，占红团恒星的3%。 我们的研究结果建议重新定义红团恒星的锂丰富度极限，即 A(Li)$> -0.9$dex，这一值远低于数十年来使用的 A(Li)$> +1.5$dex 极限（Brown等，1989；Castilho等，1995；Reddy等，2005；Carlberg等，2016；Casey等，2019；Holanda等，2020）。 显示英文摘要

摘要： The vast majority of stars with mass similar to the Sun are expected to only destroy lithium over the course of their lives, via low-temperature nuclear burning. This has now been supported by observations of hundreds of thousands of red giant stars (Brown et al. 1989, Kumar et al. 2011, Deepak et al. 2019, Singh et al. 2019, Casey et al. 2019). Here we perform the first large-scale systematic investigation into the Li content of stars in the red clump phase of evolution, which directly follows the red giant branch phase. Surprisingly we find that all red clump stars have high levels of lithium for their evolutionary stage. On average the lithium content increases by a factor of 40 after the end of the red giant branch stage. This suggests that all low-mass stars undergo a lithium production phase between the tip of the red giant branch and the red clump. We demonstrate that our finding is not predicted by stellar theory, revealing a stark tension between observations and models. We also show that the heavily studied (Brown et al. 1989, Reddy et al. 2005, Kumar et al. 2011, Singh et al. 2019, Casey et al. 2019) very Li-rich giants, with A(Li) $> +1.5$ dex, represent only the extreme tail of the lithium enhancement distribution, comprising 3% of red clump stars. Our findings suggest a new definition limit for Li-richness in red clump stars, A(Li) $> -0.9$ dex, which is much lower than the limit of A(Li) $> +1.5$ dex used over many decades (Brown et al. 1989, Castilho et al. 1995, Reddy et al. 2005, Carlberg et al. 2016, Casey et al. 2019, Holanda et al. 2020).