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STELLAR ORIGINS OF EXTREMELY C-13- AND N-15-ENRICHED PRESOLAR SIC GRAINS: NOVAE OR SUPERNOVAE?

Alexander, Conel M. O’D.; Alexander, Conel M. O'D.; Jose, Jordi; Nguyen; Pignatari, Marco; Alexander, Conel M.O.D.; José, Jordi; Liu, Nan; Nguyen, Ann; Nittler, Larry R.; Wang, Jianhua

Authors

Conel M. O'D. Alexander

Jordi Jose

Nguyen

Nan Liu

Larry R. Nittler

Conel M. O’D. Alexander

Jianhua Wang

Jordi José

Ann Nguyen

Abstract

Extreme excesses of 13C (12C/13C < 10) and 15N (14N/15N < 20) in rare presolar SiC grains have been considered diagnostic of an origin in classical novae, though an origin in core collapse supernovae (CCSNe) has also been proposed. We report C, N, and Si isotope data for 14 submicron- to micron-sized 13C- and 15N-enriched presolar SiC grains (12C/13C < 16 and 14N/15N < ~100) from Murchison, and their correlated Mg–Al, S, and Ca–Ti isotope data when available. These grains are enriched in 13C and 15N, but with quite diverse Si isotopic signatures. Four grains with 29,30Si excesses similar to those of type C SiC grains likely came from CCSNe, which experienced explosive H burning occurred during explosions. The independent coexistence of proton- and neutron-capture isotopic signatures in these grains strongly supports heterogeneous H ingestion into the He shell in pre-supernovae. Two of the seven putative nova grains with 30Si excesses and 29Si depletions show lower-than-solar 34S/32S ratios that cannot be explained by classical nova nucleosynthetic models. We discuss these signatures within the CCSN scenario. For the remaining five putative nova grains, both nova and supernova origins are viable because explosive H burning in the two stellar sites could result in quite similar proton-capture isotopic signatures. Three of the grains are sub-type AB grains that are also 13C enriched, but have a range of higher 14N/15N. We found that 15N-enriched AB grains (~50 < 14N/15N < ~100) have distinctive isotopic signatures compared to putative nova grains, such as higher 14N/15N, lower 26Al/27Al, and lack of 30Si excess, indicating weaker proton-capture nucleosynthetic environments.

Journal Article Type Article
Publication Date Mar 1, 2016
Journal The astrophysical journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 820
Issue 2
Article Number ARTN 140
Pages 1-14
DOI https://doi.org/10.3847/0004-637X/820/2/140
Keywords Circumstellar matter, Meteorites, meteors, meteoroids, Novae, cataclysmic variables, Nuclear reactions, nucleosynthesis, abundances, Supernovae : general
Publisher URL http://iopscience.iop.org/article/10.3847/0004-637X/820/2/140/meta;jsessionid=B8DC1164C361EE2A57E08ADFC0827F85.c2
Copyright Statement © 2016. The American Astronomical Society. All rights reserved.
Additional Information This is a copy of an article published in the Astrophysical Journal, 2016, v.820 issue 2.

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