CHEMICAL COMPOSITION OF THE OLD GLOBULAR CLUSTERS NGC 1786, NGC 2210, AND NGC 2257 IN THE LARGE MAGELLANIC CLOUD
- Dipartimento di Astronomia, Universita degli Studi di Bologna, Via Ranzani, 1-40127 Bologna (Italy)
- INAF-Osservatorio Astronomico di Bologna, Via Ranzani, 1-40127 Bologna (Italy)
This paper presents the chemical abundance analysis of a sample of 18 giant stars in three old globular clusters in the Large Magellanic Cloud (LMC), NGC 1786, NGC 2210, and NGC 2257. The derived iron content is [Fe/H] = -1.75 {+-} 0.01 dex ({sigma} = 0.02 dex), -1.65 {+-} 0.02 dex ({sigma} = 0.04 dex), and -1.95 {+-} 0.02 dex ({sigma} = 0.04 dex) for NGC 1786, NGC 2210, and NGC 2257, respectively. All the clusters exhibit similar abundance ratios, with enhanced values ({approx}+0.30 dex) of [{alpha}/Fe], consistent with the Galactic halo stars, thus indicating that these clusters have formed from a gas enriched by Type II supernovae. We also found evidence that r-process is the main channel of production of the measured neutron capture elements (Y, Ba, La, Nd, Ce, and Eu). In particular, the quite large enhancement of [Eu/Fe] ({approx}+0.70 dex) found in these old clusters clearly indicates a relevant efficiency of the r-process mechanism in the LMC environment.
- OSTI ID:
- 21452879
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 717; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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