Abundances in giant stars of the globular cluster 
 NGC 6752

Yong, David; Grundahl, F.; Nissen, P. E.; Jensen, Hannes; Lambert, David L.

doi:10.1051/0004-6361:20052916

Cited by 158 publications

(256 citation statements)

References 129 publications

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“…It was not until the comprehensive study of Sneden et al (1991) that this trend was clearly defined in a robust way, resting on measurements in a large sample of stars. Recent studies of field (Mishenina et al 2002;Bihain et al 2004) and Globular Cluster stars (Shetrone et al 2001(Shetrone et al , 2003Simmerer et al 2003;Yong et al 2005) have confirmed this trend (see Fig. 1 of Bisterzo et al 2004).…”

Section: Introductionmentioning

confidence: 69%

“…For NGC 6752 we can rely on the recent analysis by Yong et al (2005), who analysed 38 giants in this cluster, making use of high-resolution high-S/N ratio UVES spectra. The atomic data used by Yong et al (2005) are the same as those here used. The analysis is based on 1D ATLAS models and LTE spectrum synthesis.…”

Section: Observations and Equivalent Width Measurementsmentioning

confidence: 99%

“…The analysis is based on 1D ATLAS models and LTE spectrum synthesis. That the ATLAS models employed by Yong et al (2005) use the approximate overshooting option in ATLAS, while those we use do not, brings about only minor differences. Thus the measurements of Yong et al (2005) are directly comparable to our own.…”

Section: Observations and Equivalent Width Measurementsmentioning

confidence: 99%

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Cu i resonance lines in turn-off stars of NGC 6752 and NGC 6397

Bonifacio

Caffau

Ludwig

2010

A&A

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Context.Copper is an element whose interesting evolution with metallicity is not fully understood. Observations of copper abundances rely on a very limited number of lines, the strongest are the Cu i lines of Mult. 1 at 324.7 nm and 327.3 nm which can be measured even at extremely low metallicities. Aims. We investigate the quality of these lines as abundance indicators. Methods. We measure these lines in two turn-off (TO) stars in the Globular Cluster NGC 6752 and two TO stars in the Globular Cluster NGC 6397 and derive abundances with 3D hydrodynamical model atmospheres computed with the CO5BOLD code. These abundances are compared to the Cu abundances measured in giant stars of the same clusters, using the lines of Mult. 2 at 510.5 nm and 578.2 nm. Results. The abundances derived from the lines of Mult. 1 in TO stars differ from the abundances of giants of the same clusters. This is true both using CO5BOLD models and using traditional 1D model atmospheres. The LTE 3D corrections for TO stars are large, while they are small for giant stars.Conclusions. The Cu i resonance lines of Mult. 1 are not reliable abundance indicators. It is likely that departures from LTE should be taken into account to properly describe these lines, although it is not clear if these alone can account for the observations. An investigation of these departures is indeed encouraged for both dwarfs and giants. Our recommendation to those interested in the study of the evolution of copper abundances is to rely on the measurements in giants, based on the lines of Mult. 2. We caution, however, that NLTE studies may imply a revision in all the Cu abundances, both in dwarfs and giants.

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Section: Introductionmentioning

confidence: 69%

Section: Observations and Equivalent Width Measurementsmentioning

confidence: 99%

Section: Observations and Equivalent Width Measurementsmentioning

confidence: 99%

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Cu i resonance lines in turn-off stars of NGC 6752 and NGC 6397

Bonifacio

Caffau

Ludwig

2010

A&A

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“…The average number of Fe i and Fe ii lines measured in a given star was 29 and 3, respectively. Following Yong et al (2005), we estimate that the internal uncertainties in T eff , log g and ξt are 30 K, 0.1 a The digits to the left of the decimal point are the atomic number. The digit to the right of the decimal point is the ionization state ("0" = neutral, "1" = singly ionised).…”

Section: Discussionmentioning

confidence: 99%

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Yong¹,

Grundahl²,

Norris³

2014

Monthly Notices of the Royal Astronomical Society

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We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O) = 8.16 ± 0.10 (σ = 0.34) and 7.62 ± 0.02 (σ = 0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of four (∼0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances.

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“…Furthermore, Smith et al (2005) noted that stars in M4 showed evidence for a Na-F anticorrelation (an F spread was also found in NGC 6712; Yong et al 2008a), while Pasquini et al (2005) and Bonifacio et al (2007) found a Na-Li anticorrelation in NGC 6752 and 47 Tucanae, respectively. The Mg-Al anticorrelation is of particular interest, because from data for NGC 6752 (Yong et al 2005), it is apparent that there is a larger spread in Al relative to Fe, on the order of ∼ 1 dex or more, but only a modest spread of ∼ 0.3 dex in Mg relative to Fe. A further important test for any model is determining how well it can reproduce the Mg isotopic ratios observed in GC stars (e.g., in NGC 6752; Yong et al 2003), which show a positive correlation between 26 Mg and Al, and an anticorrelation between the dominant 24 Mg and Al.…”

Section: Introductionmentioning

confidence: 99%

Globular cluster abundances: the role of asymptotic giant branch stars

Karakas

2009

Proc. IAU

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Abstract.One of the more popular theories to account for the abundance anomalies in globular cluster stars is the 'self-pollution scenario,' where the polluters were a previous generation of intermediate-mass asymptotic giant branch (AGB) stars. This idea has proved attractive because: (i) the hot-bottom burning experienced by these objects qualitatively provides an ideal proton-capture environment to produce helium and convert C and O to N, Ne to Na and Mg to Al, and (ii) the slow winds from these stars allow their retention by the cluster's gravitational potential. New stellar yields from low-metallicity AGB models are presented and compared to abundances derived in globular clusters. We also discuss external pollution and inhomogeneouspollution models that use AGB stars as polluters. Current models of AGB stars cannot match all observational features of globular cluster stars. However, stellar modelling uncertainties are considerable and suggest AGB stars should not be ruled out just yet.

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Abundances in giant stars of the globular cluster NGC 6752

Cited by 158 publications

References 129 publications

Cu i resonance lines in turn-off stars of NGC 6752 and NGC 6397

Cu i resonance lines in turn-off stars of NGC 6752 and NGC 6397

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Globular cluster abundances: the role of asymptotic giant branch stars

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