Abstract
Spectroscopic scans with the CTIO vidicon systems are described for a total of 63 stars in six globular clusters, including 47 Tuc, NGC 288, NGC 362, M15, M2, and Pal 12. Several abundance-sensitive features (calcium lines, iron lines, G band, CN bands) are synthesized from the spectra and used to determine the relative compositions of the clusters. The principal results are: (a) 47 Tuc is clearly the most metal rich system in our sample, followed in order of decreasing (Fe/H) by NGC 362, Pal 12, NGC 288, M2, and M15. Except for CN, the rankings given by the individual parameters tend to be closely consistent; (b) NGC 288, NGC 362, and Pal 12 all have nearly similar metallicities (at (Fe/H)approx.-1.2 if 47 Tuc is at -0.8 and M2 at -1.5) but strongly different average ultraviolet CN strengths. Their observed spectroscopic differences are not well correlated with their equally strong color-magnitude differences: (c) the giants in both 47 Tuc and NGC 362 have similar average CN (lambda3883) band strengths and also variable star-to-star CN strengths, at all levels along the giant branch. The more metal poor clusters show smaller CN variations.
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