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Medium-Resolution s-process Element Survey of 47 Tuc Giant Stars

Published online by Cambridge University Press:  02 January 2013

C. C. Worley  and
P. L. Cottrell
C. C. Worley*
Affiliation:
Observatoire de la Côte d'Azur, B.P. 4229, Nice, Cedex 04, France
P. L. Cottrell
Affiliation:
The Beatrice Tinsley Institute, Department of Physics & Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Max Planck Institut für Astrophysik, Karl-Schwarzschild Str 1, 85741, Garching, Germany
*
DCorresponding author. Email: cworley@oca.eu
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Abstract

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Medium-resolution (R ∼ 6500) spectra of 97 giant stars in the globu lar cluster 47 Tucanæ (47 Tuc) have been used to derive the C- and N-abundance sensitive index, δC, 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 effective temperature ( Teff) and surface gravity (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 (δC) values which are a measure of the CN abundance. The δC index is shown to be correlated with Na abundance for this sample, confirming previous studies. Fe, Ca, Si and the light and heavy s-process (slow neut ron capture) elements, Zr and Ba, respectively, have a narrow range of abundance values, indicative of a homogeneous abundance within this population of stars. The constancy of many element abundances (Fe, Si, Ca, Zr, Ba) and the δC 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 δC population). But there is no overall metallicity change across the range of δC values at a given position in the HR diagram as has been seen in some other globular clusters.

Keywords

globular clusters: individual (47 Tuc)stars: abundancesstars: late-type
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 29 , Issue 1 , 2012 , pp. 29 - 41
Copyright
Copyright © Astronomical Society of Australia 2012

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