Kavli Affiliate: Anna Frebel
| First 5 Authors: Avrajit Bandyopadhyay, Rana Ezzeddine, Vinicius M. Placco, Anna Frebel, David S Aguado
| 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 2sigma levels. 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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