The discovery of a Li-Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars?. (arXiv:1901.00048v1 [astro-ph.SR])

The discovery of a Li-Na-rich giant star in Omega Centauri: formed from the pure ejecta of super-AGB stars?. (arXiv:1901.00048v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mucciarelli_A/0/1/0/all/0/1">A. Mucciarelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Monaco_L/0/1/0/all/0/1">L. Monaco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonifacio_P/0/1/0/all/0/1">P. Bonifacio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Salaris_M/0/1/0/all/0/1">M. Salaris</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fu_X/0/1/0/all/0/1">X. Fu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Villanova_S/0/1/0/all/0/1">S. Villanova</a>

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.

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