Kavli Affiliate: Anna Frebel
| Summary:
Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red giant stars from the metal-poor globular cluster NGC 2298 using the newly commissioned GHOST spectrograph at Gemini South. We derived stellar parameters and abundances for 36 species across 32 elements, including 16 neutron-capture elements. We find that the stars exhibit chemical anomalies among the light elements, allowing us to classify them into first-generation (8 stars) and second-generation (5 stars). We derive a mean cluster metallicity of [Fe/H]=-1.98 +/- 0.10 with no significant variation among cluster members. Most alpha- and Fe-peak elements display low star-to-star abundance dispersion, with notable exceptions for Sc, Ni, and Zn for which the dispersions in Sc vary significantly between stars from different generations to 2σlevels. Similarly, among the neutron-capture elements, we observed considerable differences in dispersion for Sr and Eu among the first and second generation stars to 2 sigma levels. We also confirm an intrinsic scatter beyond observational uncertainties for several elements using a maximum likelihood approach among stars from different generations. Additionally, we note an increase in [Sr/Eu] and [Ba/Eu] with [Mg/Fe] in first-generation stars indicating correlations between the productions of light r-process and Mg. We find the universal r-process pattern, but with larger dispersions in the main r-process than the limited-r elements. These differences in abundance dispersion, among first- and second-generation stars in NGC 2298, suggest complex and inhomogeneous early chemical enrichment processes, driven by contributions from multiple nucleosynthetic events, including massive stars and rare r-process events.
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