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arXiv 0811.4654astro-ph
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大质量恒星中的NuGrid:s过程

NuGrid: s process in massive stars

Raphael Hirschi, Urs Frischknecht, F. -K. Thielemann, Marco Pignatari, Michael Bennett, Steven Diehl, Christopher L. Fryer, Falk Herwig, Aimee Hungerford, Georg… 展开作者

Raphael Hirschi, Urs Frischknecht, F. -K. Thielemann, Marco Pignatari, Michael Bennett, Steven Diehl, Christopher L. Fryer, Falk Herwig, Aimee Hungerford, Georgios Magkotsios, Gabriel Rockefeller, Francis X. Timmes, Patrick Young

摘要:

由于中子源22 Ne的丰度较低,主要的中子毒物和减少的铁种子丰度,在非常低的金属丰度的大质量恒星中的s-过程生产预计是可以忽略不计的。然而,最近的大质量恒星模型,包括旋转的影响表明,一个强大的生产22 Ne是可能的氦核心,作为一个结果,主要的氮生产(在晕贫金属恒星观察)。使用PPN后处理代码,我们研究了这个主要的22 Ne对s过程的影响。我们发现一个大的生产的S元素之间的锶和钡,开始与恒星模型预测的初级22 Ne的量。有几个关键的反应速率的不确定性影响s-过程的效率。其中,17 O(α,γ)可能发挥关键作用,强烈影响s过程的效率,或它可能发挥微不足道的作用,根据在计算中使用的速率。我们还报告了一个新的并行(MPI)后处理代码(MPPNP)的发展,旨在遵循完整的核合成在高分辨率的网格上的恒星。我们在这里提出的第一个后处理运行从ZAMS到结束的氦燃烧的15太阳质量的模型。

英文摘要:

The s-process production in massive stars at very low metallicities is expected to be negligible due to the low abundance of the neutron source 22Ne, to primary neutron poisons and decreasing iron seed abundances. However, recent models of massive stars including the effects of rotation show that a strong production of 22Ne is possible in the helium core, as a consequence of the primary nitrogen production (observed in halo metal poor stars). Using the PPN post-processing code, we studied the impact of this primary 22Ne on the s process. We find a large production of s elements between strontium and barium, starting with the amount of primary 22Ne predicted by stellar models. There are several key reaction rate uncertainties influencing the s-process efficiency. Among them, 17O(alpha,gamma) may play a crucial role strongly influencing the s process efficiency, or it may play a negligible role, according to the rate used in the calculations. We also report on the development of a new parallel (MPI) post-processing code (MPPNP) designed to follow the complete nucleosynthesis in stars on highly resolved grids. We present here the first post-processing run from the ZAMS up to the end of helium burning for a 15 solar mass model.

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