Medium-resolution (R a?? 6500) spectra of 97 giant stars in the globu lar cluster 47 Tucan?| (47 Tuc) have been used to derive the C- and N-abundance sensitive index, ?′C, 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 (?′C) values which are a measure of the CN abundance. The ?′C 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 ?′C 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 ?′C population). But there is no overall metallicity change across the range of ?′C values at a given position in the HR diagram as has been seen in some other globular clusters.
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