Details

Autor(en) / Beteiligte

• Worley, C. C.
• Cottrell, P. L.
• McDonald, I.
• van Loon, J. Th

Titel

Heavy-element abundances in low-gravity globular cluster stars: 47 Tuc

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2010-03, Vol.402 (3), p.2060-2074

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

2010

Quelle

Access via Wiley Online Library

Beschreibungen/Notizen

• The exploration of chemical abundances in globular cluster giant branch stars has revealed element-abundance inhomogeneities between the stars. This study has investigated a sample of giant branch stars in the globular cluster 47 Tucanæ, which were observed at a resolution of R∼ 110 000 using the Ultraviolet Échelle Spectrograph on the Very Large Telescope. The analysis of these stars showed non-local thermodynamic equilibrium (non-LTE) effects on the abundances derived from the sample of atomic lines under an LTE approximation. The stellar parameters for each star were redetermined using only high-excitation-potential Fe i lines. The resulting chemical abundance analysis showed enhancements in both the light and heavy s-process element abundances with mean values of 〈[ls/Fe]〉= 0.53 ± 0.09 dex and 〈[hs/Fe]〉= 0.40 ± 0.11 dex. However, no trend was found between the ratio of the heavy to light s-process element abundances ([hs/ls]=−0.13 ± 0.14 dex) and metallicity ([Fe/H]=−0.89 ± 0.09 dex) due to the small spread in both of these values. This indicates that the heavy-element-abundance enhancements are not due to third dredge-up of internal nucleosynthesis products in these evolved stars. The source of the heavy-element enhancements is therefore primordial or pollution event related in origin.