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  1. ; ; (, Research Notes of the AAS)
    Accurate stellar ages are crucial for galactic archeology, but cannot be measured directly. Evolved red giant stars offer a solution, since their lifetimes can be inferred from their masses. Mass measurements often rely on mass proxies, such as the surface carbon-to-nitrogen ratio ([C/N]) after the first dredge-up. But this relationship is not consistent for all stars. Understanding the systematics behind these [C/N] outliers is essential for improving mass and subsequent age measurements. We analyze additional elemental abundances, such as those of s-process elements, that may indicate binary interactions. We find significant differences between typical and outlier stars, suggesting atypical or binary evolution histories for outlier stars. By accounting for such complexities in this method, more accurate stellar ages and a clearer picture of the Milky Way’s formation and evolution will be understood. 
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    Free, publicly-accessible full text available October 29, 2026