High-resolution CCD spectra of stars in globular clusters. IX. The "young" clusters Ruprecht 106 and PAL 12

Jeffrey A. Brown, George Wallerstein, Daniel Zucker

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We have performed a spectroscopic abundance analysis of two stars each in the anomalously young globular clusters Rup 106 and Pal 12. We find [Fe/H] ≃ -1.45 for Rup 106 and -1.0 for Pal 12. The abundance ratios in both clusters are peculiar in comparison to other globulars: The α-elements are not enhanced over the solar ratio. We find that oxygen in Rup 106 is also relatively low, with [O/Fe] ≃ 0.0±0.1. The similarity of the ratio of the alpha-elements to iron to the solar ratio shows that species contributed by supernovae of type Ia have "caught up" with species produced by SN II's. The similar contributions of the α-and Fe-peak species to disk stars shows that age, not metallicity, is the determining factor in the ratio of SN II/SN Ia nucleosynthesis. Galactic enrichment models show that these abundance ratios can be understood as being the result of these two clusters coming from an environment with multiple discontinuous star formation events.

Original languageEnglish
Pages (from-to)180-188
Number of pages9
JournalAstronomical Journal
Issue number1
Publication statusPublished - Jul 1997
Externally publishedYes


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