Journal
ASTROPHYSICAL JOURNAL
Volume 825, Issue 2, Pages -Publisher
IOP Publishing Ltd
DOI: 10.3847/0004-637X/825/2/88
Keywords
circumstellar matter; meteorites, meteors, meteoroids; novae, cataclysmic variables; nuclear reactions, nucleosynthesis, abundances; stars: AGB and post-AGB; supernovae: general
Categories
Funding
- NASA Earth and Space Science Fellowship [NNX12AN77H]
- NASA Grants [NNX14AG25G, NNX16AD31G, NNX13AM22G, NNX13AH08G]
- MINECO grants [AYA2013-42762-P, AYA2014-59084-P]
- AGAUR
- NSF Grant [1517541]
- NASA [12310, NNX12AN77H, 468355, NNX13AM22G, 473707, NNX13AH08G, 906741, NNX16AD31G, 683540, NNX14AG25G] Funding Source: Federal RePORTER
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1517541] Funding Source: National Science Foundation
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Presolar grains constitute the remnants of stars that existed before the formation of the solar system. In addition to providing direct information on the materials from which the solar system formed, these grains provide ground-truth information for models of stellar evolution and nucleosynthesis. Here we report the in situ identification of two unique presolar graphite grains from the primitive meteorite LaPaz Icefield 031117. Based on these two graphite grains, we estimate a bulk presolar graphite abundance of 5(-3)(+7) ppm in this meteorite. One of the grains (LAP-141) is characterized by an enrichment in C-12 and depletions in S-33,S-34, and contains a small iron sulfide subgrain, representing the first unambiguous identification of presolar iron sulfide. The other grain (LAP-149) is extremely C-13-rich and N-15-poor, with one of the lowest C-12/C-13 ratios observed among presolar grains. Comparison of its isotopic compositions with new stellar nucleosynthesis and dust condensation models indicates an origin in the ejecta of a low-mass CO nova. Grain LAP-149 is the first putative nova grain that quantitatively best matches nova model predictions, providing the first strong evidence for graphite condensation in nova ejecta. Our discovery confirms that CO nova graphite and presolar iron sulfide contributed to the original building blocks of the solar system.
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