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Title: New Constraints for Supernova Models from Presolar Silicon Carbide X Grains with Very High 26 Al/ 27 Al Ratios
Abstract

We report C, N, Mg-Al, Si, and S isotope data of six 1–3μm-sized SiC grains of Type X from the Murchison CM2 chondrite, believed to have formed in the ejecta of core-collapse supernova (CCSN) explosions. Their C, N, and Si isotopic compositions are fully compatible with previously studied X grains. Magnesium is essentially monoisotopic26Mg which gives clear evidence for the decay of radioactive26Al. Inferred initial26Al/27Al ratios are between 0.6 and 0.78 which is at the upper end of previously observed ratios of X grains. Contamination with terrestrial or solar system Al apparently is low or absent, which makes the X grains from this study particularly interesting and useful for a quantitative comparison of Al isotope data with predictions from supernova models. The consistently high26Al/27Al ratios observed here may suggest that the lower26Al/27Al ratios of many X grains from the literature are the result of significant Al contamination and in part also of an improper quantification of26Al. The real dispersion of26Al/27Al ratios in X grains needs to be explored by future studies. The high observed26Al/27Al ratios in this work provide a crucial constraint for the production of26Al in CCSN models. We explored different CCSN models, including both “classical” and H ingestion CCSN models. It is found that the classical models cannot account for the high26Al/27Al ratios observed here; in contrast, H ingestion models are able to reproduce the26Al/27Al ratios along with C, N, and Si isotopic ratios reasonably well.

 
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Award ID(s):
1927130
NSF-PAR ID:
10394740
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal Letters
Volume:
943
Issue:
2
ISSN:
2041-8205
Format(s):
Medium: X Size: Article No. L22
Size(s):
["Article No. L22"]
Sponsoring Org:
National Science Foundation
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