An Abundance Analysis of Bright Giants in the Globular Cluster NGC 1851

By David Yong, F. Grundahl. 2007

138 citations recorded by the source corpus.

We present the chemical compositions for eight bright giants in the globular cluster NGC 1851. Our analysis reveals large star-to-star abundance variations and correlations of the light elements O, Na, and Al, a feature found in every well-studied globular cluster. However, NGC 1851 also exhibits large star-to-star abundance variations of the s-process elements Zr and La. These s-process elements are correlated with Al and anticorrelated with O. Furthermore, the Zr and La abundances appear to cluster around two distinct values. A recent study revealed a double subgiant branch in NGC 1851. Our data reinforce the notion that there are two stellar populations in NGC 1851 and indicate that this cluster has experienced a complicated formation history with similarities to ω Centauri.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/31c624bde5d21d388777343e135f90abf0da0228

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In Astronomy and Astrophysics

1. Martin Asplund
2. R. Gratton
3. E. Carretta
4. A. Bragaglia
5. G. Piotto
6. F. D’Antona
7. A. Milone
8. L. Bedin

In Instrumentation

1. R. Gratton
2. E. Carretta
3. A. Bragaglia
4. F. D’Antona
5. G. Piotto
6. A. Milone
7. L. Bedin
8. A. Renzini

Citations in the corpus

• The Gaia-ESO Survey: the analysis of high-resolution UVES spectra of FGK-type stars (2014, methodology): “…method-to-method dispersion of each parameter we decided to use the median and the associated MAD (median absolute devi- 13 For example, NGC 1851 seems to present a small dispersion in metallicity and star-to-star variations of s-process elements (Yong & Grundahl 2008; Carretta et al. 2011) ation).”
• Spectroscopic and photometric evidence of two stellar populations in the Galactic globular cluster NGC 6121 (M 4) (2008, background): “In NGC 1851 the presence of a group f RGB stars with enhanced Sr and Ba and strong CN bands, mong the majority of CN-normal RGB stars (Yong & Grundahl 2008), and the presence of a bimodal HB, agrees with the hypothesis of two stellar generations inferred by the observed SGB split.”
• Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, background): “This is the only cluster in which a bimodal spread in the abundance of s-process elements has also been found, anticorrelated with the oxygen abundance (Yong & Grundahl 2008).”
• The two metallicity groups of the globular cluster M 22: a chemical perspective (2011, background): “Like M22, there is a bimodality in s-process elements (Yong & Grundahl 2008), a possible spread in [Fe/H] metallicity and [Ca/H], a segregation of stars in color-magnitude diagram quantities that correlates with abundance variations (Milone et al. 2008, Han et al. 2009).”
• Multiple populations in globular clusters (2012, background): “2008) and spectroscopy (Yong and Grundahl 2008; Villanova et al. 2010; Carretta et al. 2011a) in the peculiar cluster NGC 1851, characterised by a small difference of Fe and a larger spread in Ba, positively correlated with metallicity, as the enhancement in s-process elements is higher in the more ”
• A double stellar generation in the globular cluster NGC 6656 (M 22): Two stellar groups with different iron and s-process element abundances (2009, background): “Unfortunately, for both of these clusters, the available chemical measurements from high resolution spectroscopy are limited to seven RGB stars for NGC 6388 (Carretta et al. 2007) and eight RGB stars for NGC 1851 (Yong & Grundahl 2008).”
• The SUMO project: a SUrvey of Multiple pOpulations in globular clusters (2013, background): “These components contain ∼25% (population a),∼45% (population b), and∼30% (population c) of the cluster stars (see e.g. Norris 1981; Grundahl et al.2002; Yong et al. 2005; Carretta et al. 2007; Yong & Grundahl 2008; Carretta et al. 2012, for spectroscopic studies on stellar populations in NGC 6752).”
• Origin of multiple stellar populations in globular clusters and their helium enrichment (2008, background): “O anticorrelation and variations of the s-process elements (Yong & Grundahl 2008).”
• The fraction of second generation stars in globular clusters from the analysis of the horizontal branch (2008, background): “The recent new data by Yong & Grundahl (2008), on the contrary, contain also nitrogen normal stars.”