Abundances in giant stars of the globular cluster NGC 6752

By D. Yong, F. Grundahl, P. Nissen, H. R. Jensen, D. Austin, University of North Carolina, U. Aarhus. 2005

207 citations recorded by the source corpus.

Recent theoretical yields and chemical evolution models demonstrate that intermediate-mass AGB stars cannot reproduce the observed abundance distributions of O, Na, Mg, and Al. As a further observational test of this finding, we present elemental abundance ratios [X/Fe] for 20 elements in 38 bright giants of the globular cluster NGC 6752 based on high-resolution, high signal-to-noise spectra obtained with UVES on the VLT. This is the most complete spectroscopic analysis of this cluster in terms of the number of elements considered and the number of stars in the sample. The stars span more than 1000 K in effective temperature and more than 3 visual magnitudes along the red giant branch. None of the abundance ratios [X/Fe] show a correlation with evolutionary status. For Si and heavier elements, the small scatter in [X/Fe] may be attributable to the measurement uncertainties. Our mean abundance ratios [X/Fe] are in good agreement with previous studies of this cluster and are also consistent with other globular clusters and field stars at the same metallicity. The mean abundance ratios [Ba/Eu] and [La/Eu] exhibit values, in agreement with field stars at the same metallicity, that lie approximately midway between the pure r -process and the solar ( s -process + r -process) mix, indicating that AGB stars have played a role in the chemical evolution of the proto-cluster gas.  For the first time, we find possible evidence for an abundance variation for elements heavier than Al in this cluster. We find a correlation between [Si/Fe] and [Al/Fe] which is consistent with the abundance anomalies being synthesized via proton captures at high temperatures. Leakage from the Mg-Al chain into 28 Si may explain the Si excess in stars with the highest [Al/Fe]. We identify correlations between [Y/Fe] and [Al/Fe], [Zr/Fe] and [Al/Fe], and [Ba/Fe] and [Al/Fe] suggesting that Y, Zr, and Ba abundances may increase by about 0.1 dex as Al increases by about 1.3 dex. While the correlations are statistically significant, the amplitudes of the variations are small. If the small variations in Y, Zr, and Ba are indeed real, then the synthesis of the Al anomalies must have taken place within an unknown class of stars that also ran the s -process.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/860b3c16305684831ae0b4ab61ee0ac462b9bb1d

Citations in the corpus

Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, unknown): “The explanation for this behaviour is given by Yong et al. (2005) in their study of giants in NGC 6752.”
Multiple populations in globular clusters (2012, unknown): “…6397 (Korn et al. 2007; Carretta et al. 2009a,b; Lind et al. 2011); NGC 6388 (Carretta et al. 2007c); NGC 6441 (Gratton et al. 2006, 2007); NGC 6712 (Yong et al. 2008); M 4 (Smith et al. 2005b; Marino et al. 2008; Carretta et al. 2009a,b; Monaco et al. 2011); M 22 (Marino et al. 2009, 2011b); NGC…”
Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters (2006, unknown): “However the predicted magnesium isotopic ratios are still in conflict with the data by Yong et al. (2003, 2005).”
MULTIPLE STELLAR POPULATIONS IN 47 Tucanae (2011, unknown): “Yong et al. (2008) found that RGB spreads are present in a large number of GCs, when using the Strömgren c1 index, which is a powerful tracer of the N abundance.”
Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus (2010, unknown): “The proton-capture reactions involving Mg, Al (and Si, see Yong et al. 2005; Carretta et al. 2009b) require a much higher temperature regime and consequently allow us to probe the contribution from polluters of, on average, higher mass. Al abundances were derived from the subordinate doublet at…”
Abundance patterns of multiple populations in globular clusters: a chemical evolution model based on yields from AGB ejecta (2010, unknown): “This is consistent with previous determinations, e.g. for NGC 6752 (σ=0.02 Yong et al. 2005), and for the clusters examined by Kraft & Ivans (2003) (0.03 – 0.10 dex).”
The SUMO project: a SUrvey of Multiple pOpulations in globular clusters (2013, unknown): “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).”
A WFC3/HST VIEW OF THE THREE STELLAR POPULATIONS IN THE GLOBULAR CLUSTER NGC 6752 (2013, unknown): “Since carbon abundance was not measured by Yong et al. (2008) we adopted the [C/Fe] values from Carretta et al. (2005) and take [C/Fe]=0.15 for population a, and [C/Fe]=−0.15 for both population b, and c.”
THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. I. OVERVIEW OF THE PROJECT AND DETECTION OF MULTIPLE STELLAR POPULATIONS (2014, unknown): “Previous studies, based on spectroscopy and ground-based photometry have shown that Ströemgren and ultraviolet photometry does a good job in separating multiple populations along the RGB on nearbly GCs (e.g. Yong et al. 2008; Marino et al. 2008).”
Properties of stellar generations in globular clusters and relations with global parameters (2010, unknown): “In Paper VIII we demonstrated that the ratio [Si/Fe]max is an additional marker of second-generation stars, because of the leakage of the Mg-Al cycle which produces 28Si at temperatures in excess of about 65 million K (Carretta et al. 2009b; Arnould et al. 1999; Yong et al. 2005).”
The second and third parameters of the horizontal branch in globular clusters (2010, unknown): “…this data set with a few GCs from the literature (Shetrone & Keane 2000 for NGC 362; Sneden et al. 2004 and Cohen & Melendez 2005 for NGC 5272 and NGC 6205; Sneden et al. 1991, 2000 for NGC 6341; Marino et al. 2008 for NGC 6121; Marino et al. 2009 for NGC 6656; and Yong et al. 2005 for NGC 6752).”
Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems (2014, unknown): “S R ] 1 1 Se et al. 2012), intermediate- and narrow-band photometry is more limited in this respect, although still very informative (e.g., Mould & Bessell 1982; Bonnell & Bell 1982; Yong et al. 2008; Árnadóttir et al. 2010; Casagrande et al. 2014a).”
The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, unknown): “Yong et al. (2008) find that N abundances in the giant stars of the GC NGC 6752 are positively correlated with Si, Al and Na, indicating breakout of the Mg-Al chain.”
Photometric signatures of multiple stellar populations in galactic globular clusters (2011, unknown): “In comparison with observations we find that our MV − cydiagram closely follows empirical results by Yong et al. (2008) and Lind et al. (2010), which adds support to our theoretical models.”
Origin of multiple stellar populations in globular clusters and their helium enrichment (2008, unknown): “For example, from the strength of the NH bands among RGB stars in NGC 6752 Yong et al. (2008) infer that the nitrogen abundance among the sample stars spans almost two orders of magnitude, with no obvious bimodality.”
Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra (2009, unknown): “…are of poorer quality and we only got upper limits to O abundances for quite a large fraction of the stars, the high-resolution/high S/N data by Yong et al. (2005) show that our upper limits in O can be safely considered as actual measures and that very few or no super O-poor stars of the E…”
Intrinsic iron spread and a new metallicity scale for globular clusters (2009, unknown): “…are found to differ in abundances of light elements (C, N, O, Na, Mg, Al, Si, F; Smith & Martell 2003; Smith et al. 2005; Carretta et al. 2009a,b; Yong et al. 2008a,b; Melendez & Cohen 2009, to quote a few studies; see also Gratton et al. 2004, and references therein) involved in proton-capture…”
New constraints on the chemical evolution of the solar neighbourhood and galactic disc(s) - improved astrophysical parameters for the Geneva-Copenhagen Survey (2011, unknown): “(2) and (3) to [M/H], the scatter of the resulting calibrations decreases to 0.07 and 0.10 dex respectively, thus suggesting (cf. e.g., Yong et al. 2008) that Strömgrenindices carry information on the overall metal content (apartfrom a few of the most metal-poor stars in the sample, which…”
An Abundance Analysis of Bright Giants in the Globular Cluster NGC 1851 (2007, unknown): “The hint of a correlation between Al and Zr has also been found in NGC 6752 (Yong et al. 2005).”