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Abstract 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 (eight stars) and second generation (five stars). We derive a mean cluster metallicity of [Fe/H] = −1.98 ± 0.10 with no significant variation among cluster members. Mostα- 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 2σlevels. 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 lightrprocess and Mg. We find the universalr-process pattern, but with larger dispersions in the mainrprocess than the limited-relements. 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 rarer-process events.
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r-process Abundance Patterns in the Globular Cluster M92
Abstract Whereas light-element abundance variations are a hallmark of globular clusters, there is little evidence for variations in neutron-capture elements. A significant exception is M15, which shows a star-to-star dispersion in neutron-capture abundances of at least one order of magnitude. The literature contains evidence both for and against a neutron-capture dispersion in M92. We conducted an analysis of archival Keck/HIRES spectra of 35 stars in M92, 29 of which are giants, which we use exclusively for our conclusions. M92 conforms to the abundance variations typical of massive clusters. Like other globular clusters, its neutron-capture abundances were generated by ther-process. We confirm a star-to-star dispersion inr-process abundances. Unlike M15, the dispersion is limited to “first-generation” (low-Na, high-Mg) stars, and the dispersion is smaller for Sr, Y, and Zr than for Ba and the lanthanides. This is the first detection of a relation between light-element and neutron-capture abundances in a globular cluster. We propose that a source of the mainr-process polluted the cluster shortly before or concurrently with the first generation of star formation. The heavierr-process abundances were inhomogeneously distributed while the first-generation stars were forming. The second-generation stars formed after several crossing times (∼0.8 Myr); hence, the second generation shows nor-process dispersion. This scenario imposes a minimum temporal separation of 0.8 Myr between the first and second generations.
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- PAR ID:
- 10473568
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 958
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 45
- Size(s):
- Article No. 45
- Sponsoring Org:
- National Science Foundation
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