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arXiv 1002.2346astro-ph.SR
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核塌缩超新星高熵风中的带电粒子和中子俘获过程

Charged-Particle and Neutron-Capture Processes in the High-Entropy Wind of Core-Collapse Supernovae

K. Farouqi, K. -L. Kratz, B. Pfeiffer, T. Rauscher, F. -K. Thilemann, J. W. Truran

摘要:

天体物理学网站的r-过程仍然是不确定的,这一过程的系统性,在其依赖于核性质的稳定性,在现实的恒星环境中的中子滴线方面的全面探索仍有待进行。足够高的中子与种子比只能在非常富中子的低熵环境或中等富中子的高熵环境中获得,与中子星合并(或中子星物质的喷流)和核心坍缩超新星爆炸的高熵风有关。由于化学演化模型似乎不利于中子星合并,我们在这里集中在高熵环境的熵$S$,电子丰度$Y_e$和膨胀速度$V_{exp}$。我们调查的带电粒子反应的终止点,我们定义了一个最大熵$S_{final}$为一个给定的$V_{exp}$和$Y_e$,超过该种子生产的重元素失败,由于非常小的物质密度。然后,我们调查是否r-过程之后的带电粒子冻结出原则上可以理解的基础上的经典方法,它假设中子捕获和光致衰变之间的化学平衡,可能其次是一个$β$流平衡。特别是,我们说明了多长时间这样的化学平衡近似,如何冻结从这样的条件影响的丰度模式,以及后期捕获的中子源自$β$延迟中子发射可以发挥的作用。

英文摘要:

The astrophysical site of the r-process is still uncertain, and a full exploration of the systematics of this process in terms of its dependence on nuclear properties from stability to the neutron drip-line within realistic stellar environments has still to be undertaken. Sufficiently high neutron to seed ratios can only be obtained either in very neutron-rich low-entropy environments or moderately neutron-rich high-entropy environments, related to neutron star mergers (or jets of neutron star matter) and the high-entropy wind of core-collapse supernova explosions. As chemical evolution models seem to disfavor neutron star mergers, we focus here on high-entropy environments characterized by entropy $S$, electron abundance $Y_e$ and expansion velocity $V_{exp}$. We investigate the termination point of charged-particle reactions, and we define a maximum entropy $S_{final}$ for a given $V_{exp}$ and $Y_e$, beyond which the seed production of heavy elements fails due to the very small matter density. We then investigate whether an r-process subsequent to the charged-particle freeze-out can in principle be understood on the basis of the classical approach, which assumes a chemical equilibrium between neutron captures and photodisintegrations, possibly followed by a $β$-flow equilibrium. In particular, we illustrate how long such a chemical equilibrium approximation holds, how the freeze-out from such conditions affects the abundance pattern, and which role the late capture of neutrons originating from $β$-delayed neutron emission can play.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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