On the Carbon and Nitrogen Abundances of 47 Tucanae's Main-Sequence Stars

Briley, Michael M.; Harbeck, Daniel; Smith, Graeme H.; Grebel, Eva K.

doi:10.1086/381912

Cited by 80 publications

(98 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A clearly bimodal anticorrelation is detected here (Fig. 7), which confirms the results by Harbeck et al (2003) and Briley et al (2004a) and which, together with the double SGB and wide MS found by Anderson et al (2009), demonstrates the presence of two distinct populations in this cluster.…”

Section: Ncg 104 (47 Tucanae)supporting

confidence: 90%

“…Various studies identified CN bimodalities among red giants of M 3 and M 13 (Suntzeff 1981;Briley et al 2004b), NGC 6752 (Norris et al 1981), ω Cen (Cohen & Bell 1986), NGC 6934 (Smith & Bell 1986), NGC 6171 (Smith 1988), M 71 (Smith & Penny 1989;Lee 2005), M 2 (Smith & Mateo 1990), M 5 (Ramírez & Cohen 2002), NGC 288 and NGC 362 (Kayser et al 2008), NGC 6121 (Marino et al 2008), NGC 6356, and NGC 6528 (Martell & Smith 2009), among others. Bimodalities among MS and sub-giant branch stars have also been found in M 71 (Cohen 1999), 47 Tuc (Cannon et al 1998;Harbeck et al 2003;Briley et al 2004a;Carretta et al 2005), and NGC 6752 .…”

Section: Ch and Cn Bimodalitiesmentioning

confidence: 72%

“…These calculations will be the subject of a future paper. Indeed, such a bimodality in C and N enhancements has been found e.g., by Briley et al (2004b) in RGB stars in M 13, or by Briley et al (2004a) in MS stars in 47 Tuc. That such bimodalities have rarely been found among red giants when the Na-O anti-correlations are considered deserves further studies.…”

Section: Ch and Cn Bimodalitiesmentioning

confidence: 85%

“…The CN-CH molecular abundances of turn-off and sub-giant stars in this cluster were also topic of a detailed study by Harbeck et al (2003) and Briley et al (2004a), resulting in a clear bimodality in band strengths and also in [N/Fe], with abundance differences of up to 1 dex. We use here their archive data to test the homogeneity of reductions.…”

Section: Ncg 104 (47 Tucanae)mentioning

confidence: 95%

See 3 more Smart Citations

Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters

Pancino

Rejkuba²,

Zoccali

et al. 2010

A&A

164

View full text Add to dashboard Cite

Context. Globular clusters show star-to-star abundance variations for light elements that are not yet well understood. The preferred explanation involves a self-enrichment scenario, within which two subsequent generations of stars co-exist in globular clusters. Observations of chemical abundances in the main sequence and sub-giant branch stars allow us to investigate the signature of this chemically processed material without the complicating effects caused by stellar evolution and internal mixing. Aims. Our main goal is to investigate the carbon-nitrogen anti-correlation with low-resolution spectroscopy of 20−50 stars fainter than the first dredge-up in seven Galactic globular clusters (NGC 288, NGC 1851, NGC 5927, NGC 6352, NGC 6388, and Pal 12) with different properties. We complemented our observations with 47 Tuc archival data, with four additional clusters from the literature (M 15, M 22, M 55, NGC 362), and with additional literature data on NGC 288. Methods. In this first paper, we measured the strengh of the CN and CH band indices, which correlate with the N and C abundances, and we investigated the anti-correlation and bimodality of these indices. We compared r CN , the ratio of stars belonging to the CN-strong and weak groups, with 15 different cluster parameters. Results. We clearly see bimodal anti-correlation of the CH and CN band stregths in the metal-rich clusters (Pal 12, 47 Tuc, NGC 6352, NGC 5927). Only M 15 among the metal-poor clusters shows a clearly bimodal anti-correlation. We found weak correlations (sligthly above 1σ) of r CN with the cluster orbital parameters, present-day total mass, cluster concentration, and age. Conclusions. Our findings support the self-enrichment scenario, and suggest that the occurrence of more than two major generations of stars in a GGC should be rare. Small additional generations (<10−20% of the total) would be difficult to detect with our samples. The first generation, which corresponds to the CN-weak stars, usually contains more stars than the second one ( r CN = 0.82 ± 0.29), as opposed to results based on the Na-O anti-correlations.

show abstract

Section: Ncg 104 (47 Tucanae)supporting

confidence: 90%

Section: Ch and Cn Bimodalitiesmentioning

confidence: 72%

Section: Ch and Cn Bimodalitiesmentioning

confidence: 85%

Section: Ncg 104 (47 Tucanae)mentioning

confidence: 95%

See 2 more Smart Citations

Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters

Pancino

Rejkuba²,

Zoccali

et al. 2010

A&A

164

View full text Add to dashboard Cite

show abstract

“…While changes in [C/Fe], [N/Fe], and 12 C/ 13 C ratios as a function of evolutionary state on the subgiant branch (SGB) and red giant branch (RGB) are clearly linked to in situ mixing processes (e.g., Denissenkov & VandenBerg 2003), the temperatures reached near the bottom of the convective envelope in more evolved low-mass RGB stars are too low to significantly alter the abundances of heavier elements (but see also D'Antona & Ventura 2007 for a possible exception). Observations of similar star-to-star abundance variations among scarcely evolved globular cluster mainsequence and SGB stars (e.g., Briley et al 1996Briley et al , 2004Gratton et al 2001;Ramírez & Cohen 2002, 2003Carretta et al 2004;Cohen & Meléndez 2005;Bragaglia et al 2010;D'Orazi et al 2010;Dobrovolskas et al 2014) indicate that the composition differences between the various globular cluster populations were already imprinted on the gas from which the stars formed. Although there is still no consensus regarding the nucleosynthesis source(s) driving the composition differences, possible options include intermediate mass (∼5-8 M e ) asymptotic giant branch (AGB) stars (e.g., Karakas et al 2006;, rapidly rotating massive (20 M e ) main-sequence stars (e.g., Decressin et al 2007a), massive binary stars (de Mink et al 2009), and super massive (∼10 4 M e ) stars (Denissenkov & Hartwick 2014).…”

Section: Introductionmentioning

confidence: 99%

Agb Sodium Abundances in the Globular Cluster 47 Tucanae (Ngc 104)

Johnson

McDonald

Pilachowski

et al. 2015

View full text Add to dashboard Cite

A recent analysis comparing the [Na/Fe] distributions of red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB in NGC 6752 warrants additional investigations to determine if the failure of a significant fraction of stars to ascend the AGB is an attribute common to all globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe] abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47 Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB sample published previously. The abundances and velocities were derived from high-resolution spectra obtained with the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan-Clay 6.5 m telescope. We find the average heliocentric radial velocity and [Fe/H] values to be á ñ RV helio. = −18.56 km s −1 (σ = 10.21 km s −1 ) and á ñ [Fe H] = −0.68 (σ = 0.08), respectively, in agreement with previous literature estimates. The average [Na/Fe] abundance is 0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB. However, in contrast to NGC 6752, the two 47 Tuc populations have nearly identical [Na/Fe] dispersion and interquartile range values. The data presented here suggest that only a small fraction (20%) of Na-rich stars in 47 Tuc may fail to ascend the AGB, which is a similar result to that observed in M13. Regardless of the cause for the lower average [Na/Fe] abundance in AGB stars, we find that Na-poor stars and at least some Na-rich stars in 47 Tuc evolve through the early AGB phase. The contrasting behavior of Na-rich stars in 47 Tuc and NGC 6752 suggests that the RGB [Na/Fe] abundance alone is insufficient for predicting if a star will ascend the AGB.

show abstract

Chemical Abundance Inhomogeneities in Globular Cluster Stars

Cohen

Chemical Abundances and Mixing in Stars in the Milky Way and Its Satellites

View full text Add to dashboard Cite

It is now clear that abundance variations from star-to-star among the light elements, particularly C, N, O, Na and Al, are ubiquitous within galactic globular clusters; they appear seen whenever data of high quality is obtained for a sufficiently large sample of stars within such a cluster. The correlations and anti-correlations among these elements and the range of variation of each element appear to be independent of stellar evolutionary state, with the exception that enhanced depletion of C and of O is sometimes seen just at the RGB tip. While the latter behavior is almost certainly due to internal production and mixing, the internal mixing hypothesis can now be ruled out for producing the bulk of the variations seen. We focus on the implications of our new data for any explanation invoking primordial variations in the proto-cluster or accretion of polluted material from a neighboring AGB star.

show abstract

On the Carbon and Nitrogen Abundances of 47 Tucanae's Main-Sequence Stars

Cited by 80 publications

References 32 publications

Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters

Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters

Agb Sodium Abundances in the Globular Cluster 47 Tucanae (Ngc 104)

Chemical Abundance Inhomogeneities in Globular Cluster Stars

Contact Info

Product

Resources

About