标题： Omega Centauri中富锂富钠巨星的发现：由超AGB星纯喷发物形成？ 显示英文标题

标题： The discovery of a Li-Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars?

摘要： 我们报告了在球状星团Omega Centauri中使用GIRAFFE-FLAMES光谱发现的两颗富锂巨星（比红巨星分支上的凸起暗）。这两颗恒星的锂丰度分别为A(Li)=1.65和2.40 dex，并且它们属于该系统的主星族（[Fe/H]=-1.70和-1.82，分别对应）。 其中最富锂的一颗（编号\#25664）的钠丰度[Na/Fe]=+0.87 dex，比相同金属丰度的Omega Centauri中最富钠的恒星高约0.5 dex。 \#25664中的锂和钠化学丰度可以通过恒星在其红巨星分支演化过程中发生的高效深度额外混合来定性地解释，或者通过质量在7到8倍太阳质量之间的超巨星分支(AGB)恒星来解释。 在后一种情况下，这颗锂-钠丰富的恒星可能是由超AGB恒星的纯净喷发物质形成，在与原始物质混合之前，或者作为双星系统的一部分，在其伴星经历超AGB阶段时经历了物质转移。 在这两种情况下，这个独特天体的化学组成可能首次允许我们观察超AGB恒星内部处理过的气体的化学组成。 显示英文摘要

摘要： We report the discovery of two Li-rich giant stars (fainter than the red giant branch bump) in the stellar system Omega Centauri using GIRAFFE-FLAMES spectra. These two stars have A(Li)=1.65 and 2.40 dex and they belong to the main population of the system ([Fe/H]=--1.70 and --1.82, respectively). The most Li-rich of them (#25664) has [Na/Fe]=+0.87 dex that is ~0.5 dex higher than those measured in the most Na-rich stars of Omega Centauri of similar metallicity. The chemical abundances of Li and Na in #25664 can be qualitatively explained by deep extra mixing efficient within the star during its RGB evolution or by super-asymptotic giant branch (AGB) stars with masses between ~7 and 8 Msun. In the latter scenario, this Li-Na-rich star could be formed from the pure ejecta of super-AGB stars before the dilution with pristine material occurs, or, alternatively, be part of a binary system and experienced mass transfer from the companion when this latter evolved through the super-AGB phase. In both these cases, the chemical composition of this unique object could allow to look for the first time at the chemical composition of the gas processed in the interior of super-AGB stars.