来自12C核共振测量的恒星三元α过程的修订率
Hans O U Fynbo1, Christian A A Diget, Uffe C Bergmann
1Department of Physics and Astronomy, University of Aarhus, 8000 Arhus C, Denmark. fynbo@phys.au.dk
Nature
|January 15, 2005
概括
研究人员精确测量了三次α反应速率,这对于恒星进化和元素创造至关重要. 新的发现揭示了早期恒星更快的碳生成和超新星中改变的核合成.
科学领域:
- 核天体物理学 核天体物理学
- 恒星进化 恒星进化
- 宇宙核合成宇宙核合成
背景情况:
- 三次阿尔法过程,将三个核 (阿尔法粒子) 结合成碳-12 (12C),是恒星核合成的基础.
- 这种反应发生在具有足够中心温度的恒星中,对于确定宇宙元素丰度和超新星核心大小至关重要.
- 之前对三次α反应速率的测量不够确定,影响了天体物理模型.
研究的目的:
- 通过测量其反向过程来精确确定三次α反应速率:12C的分解成三个α粒子.
- 研究共振的作用,特别是11 MeV和9.1 MeV的共振,以及它们对反应速率的干扰效应.
- 为了重新计算在广泛的温度范围内的三次α率,并将其与标准天体物理模型进行比较.
主要方法:
- 测量反向的三次α反应:12C的分解成三个α粒子.
- 在12C衰变光谱中的共振的识别和描述.
- 使用实验数据计算从10^7 K到10^10 K的温度的三次α反应速率.
主要成果:
- 在12C衰变光谱中,确定了大约11 MeV的支配共振.
- 之前报告的9.1 MeV共振的存在没有得到证实.
- 响应之间的干扰显著影响了测量的光谱.
- 计算的三倍α率显示出与标准率的显著偏差,在5×10^7 K以下更高,在10^9 K以上更低.
结论:
- 修订后的三次α反应速率表明,早期恒星的碳生成速度是以前估计的两倍.
- 由于在高温下反应速度较低,预计超新星的核合成预测会发生修改.
- 精确确定三次α速率,我们对恒星进化和元素起源的理解得到了改进.
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