  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.
