Constraints on Nucleosynthesis from Xenon Isotopes in Presolar Material
Constraints on Nucleosynthesis from Xenon Isotopes in Presolar Material
复制标题
前太阳物质中氙同位素核合成的限制
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
G. Turner
中科院分区：
文献类型：
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作者：
J. Gilmour;G. Turner
通过将理论约束应用于前太阳颗粒氙同位素数据的三维拟合，我们表明它们强烈表明核合成过程产生“r过程”同位素，而不产生s过程同位素（128Xe, 130Xe），也不产生传统的r过程同位素136Xe。它是三种不同的核合成源之一，这三种核合成源对于解释所有前太阳物质中氙同位素数据的总体变化是必要和充分的。另一个贡献r过程同位素的来源是在纳米金刚石中发现的重同位素特征，这也存在于太阳前的碳化硅中，并且与轻同位素富集有关。纳米金刚石和碳化硅颗粒中该组分的重、轻同位素相对富集程度不同，表明母核合成过程并非不可分割地联系在一起。由于纳米金刚石中氙同位素组成的微小变化表明，在平均颗粒寿命内，两个不同的地点对早期太阳系的纳米金刚石做出了贡献，这表明IIa型超新星（SNe IIa）不是纳米金刚石的来源。得到的s过程特征与s过程路径上同位素颗粒亚群间的混合谱一致。这意味着一个纯粹的端元存在于颗粒中（尽管在分析中没有接近）。我们的方法是更普遍的，并提供了一套较少限制的数值约束，以满足所提出的核合成理论处理。
By applying theoretical constraints to three-dimensional fits of xenon isotope data from presolar grains, we show that they strongly suggest a nucleosynthesis process that produces "r-process" isotopes without producing s-process isotopes (128Xe, 130Xe) and without producing the conventional r-process isotope 136Xe. It is one of three distinct nucleosynthetic sources that are necessary and sufficient to explain the gross variation in xenon isotopic data across all presolar material. The other source contributing r-process isotopes is responsible for the heavy isotope signature identified in nanodiamonds, which is also present in presolar SiC, and is associated with light isotope enrichment. The relative enrichments of heavy and light isotopes in this component in nanodiamonds and SiC grains are different, implying that the parent nucleosynthetic processes are not inextricably linked. Because minor variations in the isotopic compositions of xenon trapped in nanodiamonds show that two distinct sites contributed nanodiamonds to the early solar system within the average grain lifetime, it is suggested that Type IIa supernovae (SNe IIa) are not the source of the nanodiamonds. The s-process signature derived is consistent with that derived from mixing lines between grain subpopulations for isotopes on the s-process path. This implies that a pure end-member is present in the grains (although not approached in analyses). Our approach is more general and provides a less restrictive set of numerical constraints to be satisfied by proposed theoretical treatments of nucleosynthesis.