AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)

Abstract

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 (M2FS) and MSpec spectrograph on the Magellan-Clay 6.5m telescope. We find the average heliocentric radial velocity and [Fe/H] values to be <RV_helio.>=-18.56 km s^-1 (sigma=10.21 km s^-1) and <[Fe/H]>=-0.68 (sigma=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. 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. [abridged]

Accepted for publication in the Astronomical Journal; 15 pages; 8 figures; 4 tables

References in corpus (25)

• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Formation and Dynamical Evolution of Multiple Stellar Generations in Globular Clusters
• New Grids of ATLAS9 Model Atmospheres
• Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-AGB end for 0.15 - 2.5 Mo stars
• A new implementation of the infrared flux method using the 2MASS catalogue
• Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• Line lists for the A2PI-X2Sigma+ (red) and {B2Sigma+-X2Sigma} (violet) Systems of CN, 13C14N, and 12C15N, and Application to Astronomical Spectra
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Star Clusters in M31: I. A Catalog and a Study of the Young Clusters
• Light, Alpha, and Fe-Peak Element Abundances in the Galactic Bulge
• A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
• A model for the Globular Cluster extreme anomalies
• A new abundance scale for the globular cluster 47 Tuc
• CNO abundances in the globular clusters NGC 1851 and NGC 6752
• The Chemical Evolution of Helium in Globular Clusters: Implications for the Self-Pollution Scenario
• The chemical composition of red giants in 47 Tucanae I: Fundamental parameters and chemical abundance patterns
• Recombination Ghosts in Littrow Configuration: Implications for Spectrographs Using Volume Phase Holographic Gratings
• On the missing second generation AGB stars in NGC6752
• Heavy Element Abundances in Giant Stars of 47 Tuc
• The helium abundance in the metal-poor globular clusters M30 and NGC6397
• The VMC Survey. XI. Radial Stellar Population Gradients in the Galactic Globular Cluster 47 Tucanae
• Blue Hook Stars in Globular Clusters
• Medium-resolution s-process Element Survey of 47 Tuc giant stars
• NLTE effects on AGB stars in 47 Tucanae

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