Medium-resolution s-process Element Survey of 47 Tuc giant stars

Abstract

Medium-resolution (R~6,500) spectra of 97 giant stars in the globular cluster 47 Tucanae (47 Tuc) have been used to derive the C and N abundance sensitive index, deltaC, and to infer abundances of several key elements, Fe, Na, Si, Ca, Zr and Ba for a sample of 13 of these stars with similar Teff and log g. These stars have stellar properties similar to the well-studied 47 Tuc giant star, Lee 2525, but with a range of CN excess (deltaC) values which are a measure of the CN abundance. The deltaC index is shown to be correlated with Na abundance for this sample, confirming previous studies. The Fe, Ca, Si and the light- and heavy-s process (slow neutron capture) elements, Zr and Ba respectively, have a narrow range of abundance values in these stars, indicative of a homogeneous abundance within this population of stars. The constancy of many element abundances (Fe, Si, Ca, Zr, Ba) and the deltaC and Na abundance correlation could imply that there has been a second era of star formation in this cluster that has revealed the products of CNO cycle burning via hot bottom burning (depletion of C, enhancement of N and the production of Na for high deltaC population). But there is no overall metallicity change across the range of deltaC values at a given position in the HR diagram that has been seen in some other globular clusters.

14 pages, 15 figures

References in corpus (6)

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• On the C and N Abundances of 47 Tucanae Main Sequence Stars
• Heavy Element Abundances in Giant Stars of 47 Tuc
• Differential chemical abundance analysis of a 47 Tuc AGB star with respect to Arcturus
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• Spectral matching for abundances and clustering analysis of stars on the giant branches of ω Centauri
• Spectral matching for abundances of 848 stars of the giant branches of the globular cluster ω Centauri
• Abundance of barium in the atmospheres of red giants in the Galactic globular cluster NGC 104 (47 Tuc)