CHARACTERIZING THE HEAVY ELEMENTS IN GLOBULAR CLUSTER M22 AND AN EMPIRICAL s-PROCESS ABUNDANCE DISTRIBUTION DERIVED FROM THE TWO STELLAR GROUPS

Journal Article · Sun Nov 20 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/742/1/37; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21612610

Roederer, I U ^[1]; Marino, A F ^[2]; Sneden, C ^[3]

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1. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
2. Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei Muenchen (Germany)
3. Department of Astronomy, University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712 (United States)

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 six red giants in M22 using the Magellan Inamori Kyocera Echelle 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 three of these stars (the 'r+s group') have an enhancement of s-process material relative to the other three 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 asymptotic giant branch (AGB) stars with M {<=} 3 M{sub Sun} and suggest an origin in more massive AGB stars capable of activating the {sup 22}Ne({alpha},n){sup 25}Mg 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.

• OSTI ID: 21612610
• Journal Information: Astrophysical Journal, Vol. 742, Issue 1; Other Information: DOI: 10.1088/0004-637X/742/1/37; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ASYMPTOTIC SOLUTIONS
DECOMPOSITION
MAGNESIUM 25
NEUTRON REACTIONS
NUCLEOSYNTHESIS
R PROCESS
S PROCESS
SOLAR SYSTEM
STARS
TELESCOPES
ZINC
ALKALINE EARTH ISOTOPES
BARYON REACTIONS
CHEMICAL REACTIONS
ELEMENTS
EVEN-ODD NUCLEI
EVOLUTION
HADRON REACTIONS
ISOTOPES
LIGHT NUCLEI
MAGNESIUM ISOTOPES
MATHEMATICAL SOLUTIONS
METALS
NUCLEAR REACTIONS
NUCLEI
NUCLEON REACTIONS
STABLE ISOTOPES
STAR EVOLUTION
SYNTHESIS