The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics
The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics
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DOI：
10.1016/j.gca.2017.06.005
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发表时间：
2018-01
影响因子：
5
通讯作者：
M. Pignatari;P. Hoppe;R. Trappitsch;Chris L. Fryer;F. Timmes;F. Timmes;F. Herwig;F. Herwig;R. Hirschi;R. Hirschi
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文献类型：
--
作者：
M. Pignatari;P. Hoppe;R. Trappitsch;Chris L. Fryer;F. Timmes;F. Timmes;F. Herwig;F. Herwig;R. Hirschi;R. Hirschi
在原始陨石中发现了富含碳的前太阳颗粒，迄今为止的同位素测量表明其中一些是核心塌陷的超新星起源地。这适用于约1-2%的前太阳碳化硅（SiC）颗粒，所谓的X型和C型颗粒，和约30%的前太阳石墨颗粒。与太阳丰度相比，X型前太阳碳化硅颗粒显示出比铁重的几种元素的异常同位素特征：最明显的是锶，锆，钼，钌和钡。我们研究了15，20和25 M的太阳金属丰度的核塌缩超新星模型的氦壳层中锆和钼同位素的核合成，并将结果与太阳前颗粒的测量结果进行了比较。我们发现恒星模型中锆和钼的同位素丰度分布很分散，但质量平均丰度与测量值在性质上相似。我们发现所有的模型都显示了相对于测量值的过量的96 Zr，但是模型的丰度受到Sr和Zr之间分馏的影响，因为90 Zr的大部分贡献是由于90 Sr的放射性衰变。一些超新星模型显示相对于太阳，95，97 Mo过剩，96 Mo贫化。从这些模型的质量平均分布显示了过剩的100钼，但这可能会减轻最近的中子俘获截面测量。我们鼓励未来的探索，以评估关键的中子俘获反应率的不确定性的影响，在于沿着当时的过程路径。
Carbon-rich presolar grains are found in primitive meteorites, with isotopic measurements to date suggesting a core-collapse supernovae origin site for some of them. This holds for about 1–2% of presolar silicon carbide (SiC) grains, so-called Type X and C grains, and about 30% of presolar graphite grains. Presolar SiC grains of Type X show anomalous isotopic signatures for several elements heavier than iron compared to the solar abundances: most notably for strontium, zirconium, molybdenum, ruthenium and barium. We study the nucleosynthesis of zirconium and molybdenum isotopes in the He-shell of three core-collapse supernovae models of 15, 20 and 25 M☉with solar metallicity, and compare the results to measurements of presolar grains. We find the stellar models show a large scatter of isotopic abundances for zirconium and molybdenum, but the mass averaged abundances are qualitatively similar to the measurements. We find all models show an excess of96Zr relative to the measurements, but the model abundances are affected by the fractionation between Sr and Zr since a large contribution to90Zr is due to the radiogenic decay of90Sr. Some supernova models show excesses of95,97Mo and depletion of96Mo relative to solar. The mass averaged distribution from these models shows an excess of100Mo, but this may be alleviated by very recent neutron-capture cross section measurements. We encourage future explorations to assess the impact of the uncertainties in key neutron-capture reaction rates that lie along then-process path.