低质量恒星核合成和混合
News from Low Mass Star Nucleosynthesis and Mixing
摘要：
在太阳前的颗粒和演化的红巨星中已经发现了轻核和中间核以及s-过程元素。其中一些核的丰度不能用典型的恒星模型来解释，需要在包层以下的非对流混合，发生在红巨星分支（RGB）和渐近巨星分支（AGB）的阶段。类似的机制似乎是必要的，以解释中子源驱动的过程的形成。我们提出了一个简短的评论这些现象，我们评论的图片出现在低质量恒星的演化和核合成的现有数据集。我们的结论包括：i）RGB和AGB星都需要深度混合; ii）这些现象以不可忽略的速度发生的建议，可能与扩散过程不相容; iii）验证银河系中丰中子核的丰度目前正在增加，与以前的预期相反，因此s过程有新的惊喜提供给我们; iv）认识到极低质量恒星对银河核合成的重要性日益增加。
英文摘要：
Light and intermediate nuclei as well as s-process elements have been detected in presolar grains and in evolved red giants. The abundances of some of these nuclei cannot be accounted for by canonical stellar models and require non-convective mixing below the envelope, occurring during the phases of the Red Giant Branch (RGB) and of the Asymptotic Giant Branch (AGB). Similar mechanisms appear to be necessary to account for the formation of the neutron source driving s processing. We present a short review of these phenomena and we comment on the picture that emerges from the set of available data on the evolution and nucleosynthesis in low mass stars. Our conclusions include: i) the need for deep mixing in both RGB and AGB stars; ii) the suggestion that these phenomena occur at a non-negligible velocity, possibly incompatible with diffusive processes; iii) the verification that the abundances of neutron-rich nuclei are presently increasing in the Galaxy, contrary to previous expectations and hence that the s process has new surprises to offer us; iv) the recognition of the growing importance of very low mass stars for Galactic nucleosynthesis.
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