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Session 71 - Globular Clusters.
Display session, Wednesday, January 15
Isotopic carbon abundances, which trace the presence of CN-cycle material in stellar atmospheres, have been determined for a sample of 4 and 5 bright red giants in the halo globular clusters NGC 288 and 362, respectively. These giants span a range in M_V between -2.2 and -1.1 and all exhibit low ^12C/^13C ratios (\leq 8). As shown previously to be the case in the metal-rich clusters 47 Tuc and M71, a preliminary analysis suggests a general correlation between ^12C/^13C ratios and CN band strengths among the NGC 288 stars. For the 362 stars, however, ^12C/^13C ratios all appear lower, with little correlation with CN. When viewed in the context of the larger range in star-to-star [O/Fe] and [C/Fe] variations observed in NGC 362 (as compared to 288), the near equilibrium ^12C/^13C ratios imply that the 362 stars have undergone a more extensive episode of deep mixing than their 288 counterparts.
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