Ne, C, N, O, Mg, and SI isotopes in single interstellar graphite grains: Multiple stellar sources for Neon-E(L)

Details Ne, C, N, O, Mg, and SI isotopes in single interstellar graphite grains: Multiple stellar sources for Neon-E(L) Ne, C, N, O, Mg, and SI isotopes in single interstellar graphite grains: Multiple stellar sources for Neon-E(L)

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.510n&link_type=abstract

Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 510-511

Computer Science

22

Graphite, Interstellar Matter, Meteoritic Composition, Murchison Meteorite, Neon, Radioactive Isotopes, Chemical Composition, Ion Probes, Supernovae, Wolf-Rayet Stars

Scientific paper

We have analyzed 21 individual graphite grains from Murchison KE3 first by ion microprobe to determine C, N, O, Mg, and Si isotopic compositions and then by laser gas extraction to determine He and Ne compositions. This work complements our initial investigation of Ne, C, and N compositions in individual SiC and graphite grains from the Murchison meteorite. Each of the grains is interstellar in origin based on isotopic anomalies in at least one element. Fifteen of the grains exhibit (18)-O excesses and high Al-26/Al-27 ratios. Of these O-19-rich grains, seven carry (22)Ne-E(L) above detection limits. Each of these gas-rich grains has negative delta Si-29 and delta Si-30 values, except for grains 751 and 563. Of the remaining six grains one with a solar O-16/O18 ratio is gas-rich (573), however, the error on its O-16/O18 ratios is quite large. Ion probe measurements were not made on (22)Ne-rich grain 099. No He and Ne-20 were detected in any of the (22)Ne-rich grains, consistent with earlier work. The upper limits of the Ne-20/Ne-22 ratios range from approximately 0.04 to 2.4. The concentration of Ne-22 in KE3 derived from the gas-rich grains is similar to that found in its parent (KE1). Based on the O compositions, a massive (presupernova)star origin for the (18)O-rich grains has been suggested. In this scenario, the excess Ne-22 could originate as SN-produced Na-22. Alternatively, the association between Ne-22 and O-18 in seven grains suggests a Ne origin from an alpha capture on O-18 in the He-shell of the pre-SN star. Supernovae, novae (KFB1 grain 161), and possibly WR stars (grain 563) appear to be required to produce Ne-E(L).

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