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We present a multi-instrument spectroscopic analysis of the unique Li/Na-rich giant star 25664 in Omega Centauri using spectra acquired with FLAMES-GIRAFFE, X-SHOOTER, UVES and HARPS. Li and Na abundances have been derived from the UVES spectrum using transitions weakly sensitive to non-local thermodynamic equilibrium and assumed isotopic ratio. This new analysis confirms the surprising Li and Na abundances of this star (A(Li) =+2.71+-0.07 dex, [Na/Fe]=+1.00+-0.05 dex). Additionally, we provide new pieces of evidence for its chemical characterisation. The 12C/13C isotopic ratio (15+-2) shows that this star has not yet undergone the extra-mixing episode usually associated with the red giant branch bump. Therefore, we can rule out the scenario of efficient deep extra-mixing during the red giant branch phase envisaged to explain the high Li and Na abundances. Also, the star exhibits high abundances of both C and N ([C/Fe]=+0.45+-0.16 dex and [N/Fe]=+0.99+-0.20 dex), not compatible with the typical C-N anticorrelation observed in globular cluster stars. We found evidence of a radial velocity variability in 25664, suggesting that the star could be part of a binary system, likely having accreted material from a more massive companion when the latter was evolving in the AGB phase. Viable candidates for the donor star are AGB stars with 3-4 Msun and super-AGB stars (~7-8 Msun), both able to produce Li- and Na-rich material. Alternatively, the star could be formed from the pure ejecta of a super-AGB stars, before the dilution with primordial gas occurs.
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
DY Cen has shown a steady fading of its visual light by about 1 magnitude in the last 40 years suggesting a secular increase in its effective temperature. We have conducted non-LTE and LTE abundance analyses to determine the stars effective temperatu
The helium-enriched (He-enriched) metal-rich red giants of Omega Centauri, discovered by Hema and Pandey using the low-resolution spectra from the Vainu Bappu Telescope (VBT) and confirmed by the analyses of the high-resolution spectra obtained from
High-resolution optical spectra are analyzed for two of the four metal rich mildly hydrogen-poor or helium-enhanced giants discovered by Hema and Pandey (2014) along with their comparison normal (hydrogen-rich) giants of Omega Cen. The strengths of t
We present a detailed spectroscopic analysis of RR Lyrae (RRL) variables in the globular cluster NGC 5139 (omega Cen). We collected optical (4580-5330 A), high resolution (R = 34,000), high signal-to-noise ratio (200) spectra for 113 RRLs with the mu