Mixing Along the Red Giant Branch in Metal-Poor Field Stars
Stellar models predict that as a small mass star evolves up the RGB, the outer convective envelope expands inward and penetrates into the CN-cycle processed interior regions (first dredge-up). Approximately, the outer 50% of the star by mass is involved in this mixing that brings to the surface mainly 13C and 14N, while the primordial 12C and fragile, light elements like Li, Be, and B are transported from the surface to the interior. Results for old disk field giants (Shetrone et al. 1993) and metal-poor stars (Sneden et al. 1986) show that the first dredge-up occurs at the predicted luminosities; however, mixing in bright giants is much more extreme than predicted by evolutionary models
KeywordsGlobular Cluster Carbon Isotope Ratio Convective Envelope Field Star Globular Cluster Star
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