Isotopic Carbon Abundances in NGC 288 and 362 Bright Giants

Session 71 - Globular Clusters.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[71.04] Isotopic Carbon Abundances in NGC 288 and 362 Bright Giants

M. M. Briley (U. Wisconsin Oshkosh), N. B. Suntzeff (CTIO), V. V. Smith (U. Texas El Passo), R. A. Bell (U. Maryland), J. Norris (MSSSO)

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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Program listing for Wednesday