The chemical composition of a regular halo globular cluster: NGC 5897
We report for the first time on the chemical composition of the halo cluster NGC 5897 (<i>R<i/><sub>⊙<sub/> = 12.5 kpc), based on chemical abundance ratios for 27 <i>α<i/>-, iron-peak, and neutron-capture elements in seven red giants. From our high-resolution, hig...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
28 April 2014
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| In: |
Astronomy and astrophysics
Year: 2014, Volume: 565 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201323119 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/201323119 Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2014/05/aa23119-13/aa23119-13.html 
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| Author Notes: | Andreas Koch and Andrew McWilliam |
| Summary: | We report for the first time on the chemical composition of the halo cluster NGC 5897 (<i>R<i/><sub>⊙<sub/> = 12.5 kpc), based on chemical abundance ratios for 27 <i>α<i/>-, iron-peak, and neutron-capture elements in seven red giants. From our high-resolution, high signal-to-noise spectra obtained with the <i>Magellan<i/>/MIKE spectrograph, we find a mean iron abundance from the neutral species of [Fe/H] = − 2.04 ± 0.01 (stat.) ± 0.15 (sys.), which is more metal-poor than implied by previous photometric and low-resolution spectroscopic studies. The cluster NGC 5897 is <i>α<i/>-enhanced (to 0.34 ± 0.01 dex) and shows Fe-peak element ratios typical of other (metal-poor) halo globular clusters (GCs) with no overall, significant abundance spreads in iron or in any other heavy element. Like other GCs, NGC 5897 shows a clear Na-O anti-correlation, where we find a prominent primordial population of stars with enhanced O abundances and approximately solar Na/Fe ratios, while two stars are Na-rich, providing chemical proof of the presence of multiple populations in this cluster. Comparison of the heavy element abundances with the solar-scaled values and the metal-poor GC M15 from the literature confirms that NGC 5897 has experienced little contribution from s-process nucleosynthesis. One star of the first generation stands out in that it shows very low La and Eu abundances. Overall, NGC 5897 is a well behaved GC showing archetypical correlations and element-patterns, with little room for surprises in our data. We suggest that its lower metallicity could explain the unusually long periods of RR Lyr that were found in NGC 5897. |
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| Item Description: | Gesehen am 25.08.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201323119 |