THE SODIUM ALUMINUM-OXYGEN ANTICORRELATION IN OMEGA-CENTAURI AND OTHER CLUSTERS

We discuss abundances of O, Na, and Al, as a function of [Fe/H], toget her with their interrelationships, from a high-dispersion, high signal -to-noise analysis of a (biased) sample of 40 red giants in the chemic ally inhomogeneous cluster omega Centauri. Accompanying the well-estab lished range in [Fe/H], which in our sample extends from -1.8 to -0.8, we find large variations of O, Na, and Al. At [Fe/H] similar to -1.5, for example, Delta[O/Fe] greater than or equal to 0.9, Delta[Na/Fe] s imilar to 0.6, and Delta[Al/Fe] similar to 1.1. More important, there are strong ([Na/Fe], [O/Fe]) and ([Al/Fe], [O/Fe]) anticorrelations, a nd a strong positive correlation between [Na/Fe] and [Al/Fe]. The simp lest explanation of these relationships is that they are produced by e volutionary mixing effects as suggested by Denisenkov and Denisenkova in the context of earlier observations of this duster and elaborated u pon by Langer, Hoffman, and Sneden for more normal ones. We comment on the importance of the relative sizes of the ranges of intracluster Na and Al variations as a possible diagnostic of putative mixing phenome na.