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Title: CARBON-RICH PRESOLAR GRAINS FROM MASSIVE STARS: SUBSOLAR {sup 12}C/{sup 13}C AND {sup 14}N/{sup 15}N RATIOS AND THE MYSTERY OF {sup 15}N

Carbon-rich grains with isotopic anomalies compared to the Sun are found in primitive meteorites. They were made by stars, and carry the original stellar nucleosynthesis signature. Silicon carbide grains of Type X and C and low-density (LD) graphites condensed in the ejecta of core-collapse supernovae. We present a new set of models for the explosive He shell and compare them with the grains showing {sup 12}C/{sup 13}C and {sup 14}N/{sup 15}N ratios lower than solar. In the stellar progenitor H was ingested into the He shell and not fully destroyed before the explosion. Different explosion energies and H concentrations are considered. If the supernova shock hits the He-shell region with some H still present, the models can reproduce the C and N isotopic signatures in C-rich grains. Hot-CNO cycle isotopic signatures are obtained, including a large production of {sup 13}C and {sup 15}N. The short-lived radionuclides {sup 22}Na and {sup 26}Al are increased by orders of magnitude. The production of radiogenic {sup 22}Ne from the decay of {sup 22}Na in the He shell might solve the puzzle of the Ne-E(L) component in LD graphite grains. This scenario is attractive for the SiC grains of type AB with {sup 14}N/{sup 15}Nmore » ratios lower than solar, and provides an alternative solution for SiC grains originally classified as nova grains. Finally, this process may contribute to the production of {sup 14}N and {sup 15}N in the Galaxy, helping to produce the {sup 14}N/{sup 15}N ratio in the solar system.« less
Authors:
 [1] ;  [2] ;  [3] ; ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklos ut 15-17, H-1121 Budapest (Hungary)
  2. Laboratory for Space Sciences and Physics Department, Washington University, St. Louis, MO 63130 (United States)
  3. Max Planck Institute for Chemistry, D-55128 Mainz (Germany)
  4. E.A. Milne Centre for Astrophysics, Dept of Physics and Mathematics, University of Hull, HU6 7RX (United Kingdom)
  5. Department of the Geophysical Sciences and Chicago Center for Cosmochemistry, Chicago, IL 60637 (United States)
  6. Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P5C2 (Canada)
  7. Computational Physics and Methods (CCS-2), LANL, Los Alamos, NM, 87545 (United States)
  8. Keele University, Keele, Staffordshire ST5 5BG (United Kingdom)
  9. The Joint Institute for Nuclear Astrophysics, Notre Dame, IN 46556 (United States)
Publication Date:
OSTI Identifier:
22518919
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 808; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALUMINIUM 26; CARBON 12; CARBON 13; CNO CYCLE; COMPARATIVE EVALUATIONS; CONCENTRATION RATIO; ELEMENT ABUNDANCE; GALAXIES; GRAPHITE; METEORITES; NEON 22; NITROGEN 14; NITROGEN 15; NUCLEOSYNTHESIS; SILICON CARBIDES; SODIUM 22; SOLAR SYSTEM; STAR EVOLUTION; SUN; SUPERNOVAE