增强的三α反应减少了超新星中的丰富质子核合成
Shilun Jin1,2,3, Luke F Roberts4,5, Sam M Austin1,2
1National Superconducting Cyclotron Laboratory, East Lansing, MI, USA.
Nature
|December 3, 2020
概括
在超新星中, 形成碳的关键反应因高密度效应而增强了十倍. 这一发现挑战了当前重元素合成的模型,特别是中微子-质子 (νp) 过程.
科学领域:
- 核天体物理学
- 恒星进化
- 元素合成
背景情况:
- 形成碳-12的三次α反应对于超新星中的重元素合成至关重要.
- 之前的研究假设霍伊尔状态共振主导了这种反应,即使在高温下也是如此.
- 在高密度的核子散射过程对三次α反应速率的影响还不清楚.
研究的目的:
- 在超新星外流中研究三次α反应速率.
- 确定核子散射过程如何影响霍伊尔状态和反应速率.
- 评估增强的三次α反应速率对核合成预测的影响,特别是中微子-质子 (νp) 过程.
主要方法:
- 对12C中的霍伊尔状态的质子和中子散射效应的理论研究.
- 在核心崩超新星外流中发现的条件下的三次α反应速率的建模.
- 将密度依赖反应速率的增强纳入核合成模拟.
主要成果:
- 到目前为止被忽视的质子和中子散射过程在超新星外流中提高了三次α反应速率.
- 这种增强的速率抑制了在最内层的喷射物质中由np过程形成的丰富重质子同位素的产生.
- 这种增强取决于不断变化的热力学条件,与之前的常数因素敏感性研究不同.
结论:
- 在高密度下,对三次α反应速率的中介贡献是显著的,必须纳入超新星核合成模型.
- 观察到的增强使人怀疑 νp 过程是太阳系和古代恒星中重元素 (例如Mo,Ru) 丰度的唯一解释.
- 需要进一步的研究来完善超新星核合成模型与这些新了解的反应动态.
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