High Resolution Spectroscopic Abundances of Red Giant Branch Stars in NGC 6681

Abstract

We obtain high resolution spectra of nine red giant branch stars in NGC 6681 and perform the first detailed abundance analysis of stars in this cluster. We confirm cluster membership for these stars based on consistent radial velocities of 214.5$\pm$3.7 km/s and find a mean [Fe/H] = -1.63$\pm$0.07 dex and [α/Fe] = 0.42$\pm$0.11 dex. Additionally, we confirm the existence of a Na-O anti-correlation in NGC 6681 and identify two populations of stars with unique abundance trends. With the use of HST photometry from Sarajedini et al. (2007) and Piotto et al. (2015) we are able to identify these two populations as discrete sequences in the cluster CMD. Although we cannot confirm the nature of the polluter stars responsible for the abundance differences in these populations, these results do help put constraints on possible polluter candidates.

16 pages, 11 figures, 8 tables, Accepted for publication in ApJ

References in corpus (20)

• The Dartmouth Stellar Evolution Database
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• NLTE determination of the aluminium abundance in a homogeneous sample of extremely metal-poor stars
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. II. The seven stellar populations of NGC7089 (M2)
• Mg line formation in late-type stellar atmospheres: I. The model atom
• Primordial r-process Dispersion in Metal-Poor Globular Clusters
• Heavy elements in Globular Clusters: the role of AGB stars
• Accretion of pristine gas and dilution during the formation of multiple-population globular clusters
• The chemical composition of red giants in 47 Tucanae I: Fundamental parameters and chemical abundance patterns
• Three discrete groups with homogeneous chemistry along the red giant branch in the globular cluster NGC 2808
• Evidence of AGB pollution in Galactic globular clusters from the Mg-Al anticorrelations observed by the APOGEE survey
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VIII. Preliminary Public Catalog Release
• Testing Metal Poor Stellar Models and Isochrones with HST Parallaxes of Metal Poor Stars

Cited by in corpus (9)

• What is a globular cluster? An observational perspective
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• The Relationship Between Globular Cluster Mass, Metallicity, and Light Element Abundance Variations
• Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569
• A stellar census in globular clusters with MUSE -- Extending the CaT-metallicity relation below the horizontal branch and applying it to multiple populations
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• Dynamical evolution of Milky Way globular clusters on the cosmological timescale I. Mass loss and interaction with the nuclear star cluster
• Gas and Cosmic-Ray Properties in the MBM 53, 54, and 55 Molecular Clouds and the Pegasus Loop as Revealed by HI Line Profiles, Dust, and Gamma-Ray Data
• Globular Cluster Intrinsic Iron Abundance Spreads: I. Catalog