论文标题
中间中子捕获过程。 iii。不同质量和金属性的AGB星星中的I过程，没有过冲
The intermediate neutron capture process. III. The i-process in AGB stars of different masses and metallicities without overshoot
论文作者
论文摘要
除了慢速（S）和快速（R）中子捕获过程之外，中间的中子捕获过程（I-Process）也被认为存在。当质子在对流氦燃烧区中混合时，就会发生这种情况，并被称为质子摄入事件（PIE）。一个可能的天体物理部位是低质量低金属性星的渐近巨型分支（AGB）期。我们提供了经历馅饼的AGB恒星网格的I过程。我们计算了12个模型，其初始质量为1、2和3 $ M _ {\ odot} $以及[fe/h] $ = -3.0 $，$ -2.5 $ $ -2.3，$ -2.3，$ -2.3，$ -2.3，$ -2.3，$ -2.0，$，带有恒星Evolution Code Code starevol的金属。我们最大程度地使用了1160种的核网络，并与化学转运方程相连。这些模拟不包括任何额外的混合过程。质子摄入发生在我们的12个AGB模型中的六个。这些模型经历了I-process核合成的特征，其中子密度为$ \ simeq 10^{14} -10^{15} $ cm $^{ - 3} $。根据PIE性能，以下两种不同的进化路径：恒星包膜很快就会丢失并且不再产生热脉冲或具有其他热脉冲的AGB相恢复。当馅饼发生，摄入的质子的质量以及在对流的包膜中稀释脉冲材料的程度时，这种行为在关键上取决于脉搏数。馅饼后的表面富集是我们模型的强大特征，并且在各种对流假设下持续存在。我们的模型可以将重型元素综合到PB，而无需任何参数化的额外混合过程，例如过冲或包含$^{13} $ c口袋。然而，尚待探讨I过程如何取决于混合过程，例如过冲，热鞘或旋转。
Alongside the slow (s) and rapid (r) neutron capture processes, an intermediate neutron capture process (i-process) is thought to exist. It happens when protons are mixed in a convective helium-burning zone, and is referred to as proton ingestion event (PIE). A possible astrophysical site is the asymptotic giant branch (AGB) phase of low-mass low-metallicity stars. We provide i-process yields of a grid of AGB stars experiencing PIEs. We computed 12 models with initial masses of 1, 2, and 3 $M_{\odot}$ and metallicities of [Fe/H] $=-3.0$, $-2.5$ $-2.3,$ and $-2.0, $ with the stellar evolution code STAREVOL. We used a nuclear network of 1160 species at maximum, coupled to the chemical transport equations. These simulations do not include any extra mixing process. Proton ingestion takes place in six out of our 12 AGB models. These models experience i-process nucleosynthesis characterized by neutron densities of $\simeq 10^{14} -10^{15}$ cm$^{-3}$. Depending on the PIE properties two different evolution paths follow: either the stellar envelope is quickly lost and no more thermal pulses develop or the AGB phase resumes with additional thermal pulses. This behaviour critically depends on the pulse number when the PIE occurs, the mass of the ingested protons, and the extent to which the pulse material is diluted in the convective envelope. The surface enrichment after a PIE is a robust feature of our models and it persists under various convective assumptions. Our models can synthesise heavy elements up to Pb without any parametrized extra mixing process such as overshoot or inclusion of a $^{13}$C-pocket. Nevertheless, it remains to be explored how the i-process depends on mixing processes, such as overshoot, thermohaline, or rotation.
