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Title: The impact of updated Zr neutron-capture cross sections and new asymptotic giant branch models on our understanding of the S process and the origin of stardust

We present model predictions for the Zr isotopic ratios produced by slow neutron captures in C-rich asymptotic giant branch (AGB) stars of masses 1.25-4 M {sub ☉} and metallicities Z = 0.01-0.03, and compare them to data from single meteoritic stardust silicon carbide (SiC) and high-density graphite grains that condensed in the outflows of these stars. We compare predictions produced using the Zr neutron-capture cross sections from Bao et al. and from n{sub T}OF experiments at CERN, and present a new evaluation for the neutron-capture cross section of the unstable isotope {sup 95}Zr, the branching point leading to the production of {sup 96}Zr. The new cross sections generally present an improved match with the observational data, except for the {sup 92}Zr/{sup 94}Zr ratios, which are on average still substantially higher than predicted. The {sup 96}Zr/{sup 94}Zr ratios can be explained using our range of initial stellar masses, with the most {sup 96}Zr-depleted grains originating from AGB stars of masses 1.8-3 M {sub ☉} and the others from either lower or higher masses. The {sup 90,} {sup 91}Zr/{sup 94}Zr variations measured in the grains are well reproduced by the range of stellar metallicities considered here, which is the same needed tomore » cover the Si composition of the grains produced by the chemical evolution of the Galaxy. The {sup 92}Zr/{sup 94}Zr versus {sup 29}Si/{sup 28}Si positive correlation observed in the available data suggests that stellar metallicity rather than rotation plays the major role in covering the {sup 90,} {sup 91,} {sup 92}Zr/{sup 94}Zr spread.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Monash Centre for Astrophysics (MoCA), Monash University, Clayton, VIC 3800 (Australia)
  2. Istituto Nazionale di Fisica Nucleare (INFN), Bari (Italy)
  3. Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
  4. Istituto Nazionale di Fisica Nucleare (INFN), Trieste (Italy)
  5. Karlsruhe Institute of Technology, Campus North, D-76021 Karlsruhe (Germany)
  6. The Department of the Geophysical Sciences, The University of Chicago, Chicago, IL 60637 (United States)
  7. Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States)
Publication Date:
OSTI Identifier:
22348310
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; BRANCHING RATIO; CAPTURE; COMPUTERIZED SIMULATION; CORRELATIONS; COSMOLOGY; CROSS SECTIONS; FORECASTING; GALAXIES; ISOTOPE RATIO; METALLICITY; NEUTRON REACTIONS; NUCLEOSYNTHESIS; S PROCESS; SILICON 28; SILICON 29; SILICON CARBIDES; SLOW NEUTRONS; STARS; ZIRCONIUM ISOTOPES