Variations in the lithium abundances of turn off stars in the globular cluster 47 Tuc

Abstract

aims: Our aim is to determine Li abundances in TO stars of the Globular Cluster 47 Tuc and test theories about Li variations among TO stars. method: We make use of high resolution (R~ 43000), high signal-to-noise ratio (S/N=50--70) spectra of 4 turn off (TO) stars obtained with the UVES spectrograph at the 8.2m VLT Kueyen telescope. results: The four stars observed, span the range 1.6<~A(Li)} <~ 2.14, providing a mean A(Li) = 1.84 with a standard deviation of 0.25 dex. When coupled with data of other two TO stars of the cluster, available in the literature, the full range in Li abundances observed in this cluster is 1.6<~A(Li)<~ 2.3. The variation in A(Li) is at least 0.6 dex (0.7 dex considering also the data available in the literature) and the scatter is six times larger than what expected from the observational error. We claim that these variations are real. A(Li) seems to be anti-correlated with A(Na) exactly as observed in NGC 6752. No systematic error in our analysis could produce such an anti-correlation. conclusions: Na production through p captures on 22Ne at temperatures in excess of 3x10^7 K and the contemporary Li destruction could result in this anti-correlation. However such nuclear processing cannot have taken place in the stars themselves, which do not reach such high temperatures, even at their centre. This points towards the processing in a previous generation of stars. The low N/O ratios in the observed stars and the apparent lack of correlation between N an Li abundances, place a strong constraint on the properties of this previous generation. Our results indicate a different behaviour among the Globular Clusters so far studied as far as the abundance patterns are concerned.

recommended for publication in A&A by the managing associate Editor

References in corpus (8)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• A probable stellar solution to the cosmological lithium discrepancy
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• First stars VII. Lithium in extremely metal poor dwarfs
• Origin of Abundance Inhomogeneity in Globular Clusters
• Heavy elements and chemical enrichment in globular clusters
• Heavy Element Abundances in Giant Stars of 47 Tuc

Cited by in corpus (12)

• The evolution of two stellar populations in globular clusters I. The dynamical mixing timescale
• The Chemical Evolution of Globular Clusters I. Reactive Elements and Non-Metals
• Globular Cluster Formation at High Density: A model for Elemental Enrichment with Fast Recycling of Massive-Star Debris
• Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
• Lithium abundances in globular cluster giants: NGC 6218 (M12) and NGC 5904 (M5)
• Light Element Discontinuities Suggest an Early Termination of Star Formation in the Globular Cluster NGC 6402 (M14)
• Big Bang Nucleosynthesis Constraints on the Self-Gravity of Pressure
• Abundance of zirconium in the globular cluster 47 Tuc: a possible Zr-Na correlation?
• Initial Li Abundances in the Protogalaxy and Globular Clusters Based upon the Chemical Separation and Hierarchical Structure Formation
• Lithium in NGC 2243 and NGC 104
• Abundance of barium in the atmospheres of red giants in the Galactic globular cluster NGC 104 (47 Tuc)
• Dynamical mixing of two stellar populations in globular clusters