Isotopic Abundances in Globular Clusters as Tests of Stellar Nucleosynthesis – Madeleine McKenzie (Carnegie Observatories)

Abstract
Magnesium isotope ratios provide a powerful probe of the origin of chemical anomalies in globular clusters. Although globular clusters were once thought to contain stars of a single chemical composition, we now know that many host multiple stellar populations with distinct abundance patterns. These variations point to high-temperature nuclear processing in an earlier generation of stars, but the nature of those stars and the enrichment mechanisms remain uncertain. In this talk, I present a high-precision spectroscopic analysis of magnesium isotope ratios in globular cluster stars. We find that stars enriched in nitrogen, sodium, and aluminium also show enhanced ^26Mg/^24Mg, but not ^25Mg/^24Mg, revealing a surprising isotopic pattern that is difficult to reproduce in current models. We also find no clear isotopic difference between stars with and without enhancements in slow neutron-capture elements. Together, these results provide new insight into the stellar sources and nuclear processes that shaped the chemistry of globular clusters.

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