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

We report the discovery of two Li-rich giant stars(fainter than the red giant branchbump) in the stellar system Omega Centauriusing GIRAFFE-FLAMES spectra. These two starshave 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 starsof Omega Centauriof similar metallicity. The chemical abundances of Li and Na in #25664 can be qualitatively explained by deep extra mixing efficient within the starduring its RGB evolution or by super- asymptotic giant branch(AGB) starswith masses between ~7 and 8 Msun. In the latter scenario, this Li-Na-rich starcould be formed from the pure ejectaof super-AGB starsbefore 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.