Characterizing the Heavy Elements in Globular Cluster M22 and an Empirical s-process Abundance Distribution Derived from the Two Stellar Groups
arXiv:1108.3868 · doi:10.1088/0004-637X/742/1/37
Abstract
We present an empirical s-process abundance distribution derived with explicit knowledge of the r-process component in the low-metallicity globular cluster M22. We have obtained high-resolution, high signal-to-noise spectra for 6 red giants in M22 using the MIKE spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. In each star we derive abundances for 44 species of 40 elements, including 24 elements heavier than zinc (Z=30) produced by neutron-capture reactions. Previous studies determined that 3 of these stars (the "r+s group") have an enhancement of s-process material relative to the other 3 stars (the "r-only group"). We confirm that the r+s group is moderately enriched in Pb relative to the r-only group. Both groups of stars were born with the same amount of r-process material, but s-process material was also present in the gas from which the r+s group formed. The s-process abundances are inconsistent with predictions for AGB stars with M =< 3 Msun and suggest an origin in more massive AGB stars capable of activating the Ne-22(alpha,n)Mg-25 reaction. We calculate the s-process "residual" by subtracting the r-process pattern in the r-only group from the abundances in the r+s group. In contrast to previous r- and s-process decompositions, this approach makes no assumptions about the r- and s-process distributions in the solar system and provides a unique opportunity to explore s-process yields in a metal-poor environment.
Accepted for publication in the Astrophysical Journal. 18 pages, 8 figures
References in corpus (21)
- A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
- Spectroscopic and Photometric evidence of two stellar populations in the Galactic Globular Cluster NGC6121 (M4)
- The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
- Discovery of HE 1523-0901, a Strongly r-Process Enhanced Metal-Poor Star with Detected Uranium
- Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
- New Rare Earth Element Abundance Distributions for the Sun and Five r-Process-Rich Very Metal-Poor Stars
- The s process in massive stars at low metallicity. Effect of primary N14 from fast rotating stars
- Both accurate and precise gf-values for FeII lines
- Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
- Nucleosynthesis in the Early Galaxy
- The double Subgiant Branch of NGC 1851: the role of the CNO abundance
- An abundance analysis of bright giants in the globular cluster NGC 1851
- Neutron-capture elements in the very metal-poor star HD88609: another st ar with excesses of light neutron-capture elements
- Improved Laboratory Transition Probabilities for Ce II, Application to the Cerium Abundances of the Sun and Five r-process Rich, Metal-Poor Stars, and Rare Earth Lab Data
- A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
- Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
- Improved Laboratory Transition Probabilities for Er II and Applications to the Erbium Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars
- Heavy element abundances in giant stars of the globular clusters M4 and M5
- Primordial r-process Dispersion in Metal-Poor Globular Clusters
- Rubidium and lead abundances in giant stars of the globular clusters M4 and M5
- Neutron-capture elements in the metal-poor globular cluster M15
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- On the distance of the globular cluster M4 (NGC 6121) using RR Lyrae stars: I. optical and near-infrared Period-Luminosity and Period-Wesenheit relations
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- A Spectroscopic Analysis of the Galactic Globular Cluster NGC 6273 (M19)
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- Heavy elements in Globular Clusters: the role of AGB stars
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- Multiple Stellar Populations of Globular Clusters from Homogenous Ca by Photometry I. M22 (NGC 6656)
- Detailed Chemical Abundances in NGC 5824: Another Metal-Poor Globular Cluster with Internal Heavy Element Abundance Variations
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- Multiple stellar populations and their evolution in globular clusters: A nucleosynthesis perspective
- NGC 5824: a luminous outer halo globular cluster with an intrinsic abundance spread
- CNO and F abundances in the globular cluster M22 (NGC 6656)
- Potassium in globular cluster stars: comparing normal clusters to the peculiar cluster NGC 2419
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- Spectroscopic analysis of the two subgiant branches of the globular cluster NGC1851
- Nucleosynthesis in helium-enriched asymptotic giant branch models: Implications for Heavy Element Enrichment in Omega Centauri
- Detailed Abundances of 15 Stars in the Metal-Poor Globular Cluster NGC 4833
- Fluorine variations in the globular cluster NGC 6656 (M22): implications for internal enrichment timescales
- The complex stellar system M 22: confirming abundance variations with high precision differential measurements
- The WAGGS project - II. The reliability of the calcium triplet as a metallicity indicator in integrated stellar light
- On the internal pollution mechanisms in the globular cluster NGC 6121 (M4): heavy-element abundances and AGB models
- Using the Multi-Object Adaptive Optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre
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- The s-Process Enrichment of the Globular Clusters M4 and M22
- Confirming the intrinsic abundance spread in the globular cluster NGC 6273 (M 19) with calcium triplet spectroscopy
- A chemical signature from fast-rotating low-metallicity massive stars: ROA 276 in omega Centauri
- Potassium abundances in multiple stellar populations of the globular cluster NGC 4833
- Single photoionization of the Zn II ion in the photon energy range 17.5 to 90.0 eV: experiment and theory
- Abundances of disk and bulge giants from high-resolution optical spectra V. Molybdenum -- the p-process element
- Single photoionization of the Kr-like Rb II ion in the photon energy range 22 - 46.0 eV
- Stellar s-process neutron capture cross section of Ce isotopes
- The complex stellar system M 22: constraining the chemical enrichment from AGB stars using magnesium isotope ratios
- Neutron-capture elements in a sample of field metal-poor N-rich dwarfs