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Cluster Analysis of Presolar Silicon Carbide Grains: Evaluation of Their Classification and Astrophysical Implications
The Astrophysical Journal Letters ( IF 7.9 ) Pub Date : 2021-01-29 , DOI: 10.3847/2041-8213/abd102
Asmaa Boujibar 1 , Samantha Howell 1, 2 , Shuang Zhang 1 , Grethe Hystad 3 , Anirudh Prabhu 4 , Nan Liu 5 , Thomas Stephan 6, 7 , Shweta Narkar 4 , Ahmed Eleish 4 , Shaunna M Morrison 1 , Robert M Hazen 1 , Larry R Nittler 1
Affiliation  

Cluster analysis of presolar silicon carbide grains based on literature data for 12C/13C, 14N/15N, δ 30Si/28Si, and δ 29Si/28Si including or not inferred initial 26Al/27Al data, reveals nine clusters agreeing with previously defined grain types but also highlighting new divisions. Mainstream grains reside in three clusters probably representing different parent star metallicities. One of these clusters has a compact core, with a narrow range of composition, pointing to an enhanced production of SiC grains in asymptotic giant branch (AGB) stars with a narrow range of masses and metallicities. The addition of 26Al/27Al data highlights a cluster of mainstream grains, enriched in 15N and 26Al, which cannot be explained by current AGB models. We defined two AB grain clusters, one with 15N and 26Al excesses, and the other with 14N and smaller 26Al excesses, in agreement with recent studies. Their definition does not use the solar N isotopic ratio as a divider, and the contour of the 26Al-rich AB cluster identified in this study is in better agreement with core-collapse supernova models. We also found a cluster with a mixture of putative nova and AB grains, which may have formed in supernova or nova environments. X grains make up two clusters, having either strongly correlated Si isotopic ratios or deviating from the 2/3 slope line in the Si 3-isotope plot. Finally, most Y and Z grains are jointly clustered, suggesting that the previous use of 12C/13C = 100 as a divider for Y grains was arbitrary. Our results show that cluster analysis is a powerful tool to interpret the data in light of stellar evolution and nucleosynthesis modeling and highlight the need of more multi-element isotopic data for better classification.



中文翻译:

太阳前碳化硅颗粒的聚类分析:对其分类和天体物理意义的评估

基于12 C/ 13 C、14 N/ 15 N、δ 30 Si/ 28 Si 和δ 29 Si/ 28 Si 的文献数据(包括或未推断的初始26 Al/ 27 Al 数据)对太阳前碳化硅晶粒进行聚类分析,揭示了九个簇与先前定义的谷物类型一致,但也突出了新的划分。主流颗粒存在于三个星团中,可能代表不同的母星金属丰度。其中一个星团具有致密的核心,成分范围较窄,这表明质量和金属丰度范围较窄的渐近巨分支(AGB)恒星中碳化硅颗粒的产量增加。添加26 Al/ 27 Al 数据突出显示了富含15 N 和26 Al的主流晶粒簇,这是当前 AGB 模型无法解释的。我们定义了两个 AB 晶粒簇,一个具有15 N 和26 Al 过量,另一个具有14 N 和较小的26 Al 过量,这与最近的研究一致。他们的定义没有使用太阳氮同位素比作为划分标准,并且本研究中确定的26富铝 AB 星团的轮廓与核心塌陷超新星模型更加一致。我们还发现了一个由假定的新星和 AB 颗粒混合而成的星团,它们可能是在超新星或新星环境中形成的。X 晶粒组成两个簇,它们要么具有强相关的 Si 同位素比率,要么偏离 Si 3 同位素图中的 2/3 斜率线。最后,大多数 Y 和 Z 晶粒共同聚集,这表明之前使用12 C/ 13 C = 100 作为 Y 晶粒的分隔符是任意的。我们的结果表明,聚类分析是根据恒星演化和核合成建模解释数据的强大工具,并强调需要更多的多元素同位素数据才能更好地分类。

更新日期:2021-01-29
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