A strong neutron burst in jet-like supernovae of spinstars
A strong neutron burst in jet-like supernovae of spinstars
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DOI：
10.1051/0004-6361/202037966
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发表时间：
2020-06
影响因子：
6.5
通讯作者：
A. Choplin;N. Tominaga;B. Meyer
中科院分区：
文献类型：
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作者：
A. Choplin;N. Tominaga;B. Meyer
上下文一些贫金属恒星的丰度模式介于慢中子捕获过程和快中子捕获过程之间。目标。我们表明，氦壳的快速旋转的大质量星星经历一个喷流般的爆炸经历了两个有效的中子捕获过程：一个在恒星演化过程中，一个在爆炸。它最终提供了一种材料，其化学成分介于s-和r-过程之间。方法.一个低金属丰度40 M的超新星模型，初始旋转速度为10700 km s−1，计算了从诞生到前超新星的过程，并在慢中子捕获过程之后使用扩展的核网络。一个二维流体动力学相对论代码被用来模拟一个E = 1052 erg的相对论射流爆炸击中恒星地幔。喷流诱导的核合成是在后处理中用1812个核的优化网络计算的。结果在这颗星星的一生中，来自30 Z的重元素会产生于一个有效的s过程，这个过程是由旋转推动的。在演化的末期，氦壳层大量富集了反式铁元素和（未燃烧的）22 Ne，其丰度比非旋转模型高出20倍。在爆炸过程中，喷流将氦壳层加热到1.5G K。它有效地激活（α，n）反应，例如22 Ne（α，n），并在0.1 s内产生中子密度为1019 - 1020 cm-3的强n过程。这会使在恒星演化过程中形成的s-过程模式向重元素（如Eu）移动。由此产生的化学图案与碳增强的贫金属r/s星星CS 29528 -028的丰度一致，前提是喷流模型的喷出物没有均匀混合。结论.旋转大质量恒星的氦燃烧区在演化过程中经历了一个有效的s过程，然后在类似喷流的爆炸过程中经历了一个有效的n过程。这是一个新的天体物理学站点，至少可以解释一些在s-和r-过程中间显示丰度模式的贫金属恒星。
Context. Some metal-poor stars have abundance patterns, which are midway between the slow (s) and rapid (r) neutron capture processes. Aims. We show that the helium shell of a fast rotating massive star experiencing a jet-like explosion undergoes two efficient neutron capture processes: one during stellar evolution and one during the explosion. It eventually provides a material whose chemical composition is midway between the s- and r-process. Methods. A low metallicity 40 M⊙ model with an initial rotational velocity of ∼700 km s−1 was computed from birth to pre-supernova with an extended nuclear network following the slow neutron capture process. A two-dimensional hydrodynamic relativistic code was used to model a E = 1052 erg relativistic jet-like explosion hitting the stellar mantle. The jet-induced nucleosynthesis was calculated in post-processing with an optimised network of 1812 nuclei. Results. During the star’s life, heavy elements from 30 ≲ Z ≲ 82 are produced thanks to an efficient s-process, which is boosted by rotation. At the end of evolution, the helium shell is largely enriched in trans-iron elements and in (unburnt) 22Ne, whose abundance is ∼20 times higher than in a non-rotating model. During the explosion, the jet heats the helium shell up to ∼1.5 GK. It efficiently activates (α, n) reactions, such as 22Ne(α, n), and leads to a strong n-process with neutron densities of ∼1019 − 1020 cm−3 during 0.1 s. This has the effect of shifting the s-process pattern, which was built during stellar evolution, towards heavier elements (e.g. Eu). The resulting chemical pattern is consistent with the abundances of the carbon-enhanced metal-poor r/s star CS29528-028, provided the ejecta of the jet model is not homogeneously mixed. Conclusions. The helium burning zones of rotating massive stars experience an efficient s-process during the evolution followed by an efficient n-process during a jet-like explosion. This is a new astrophysical site which can explain at least some of the metal-poor stars showing abundance patterns midway between the s- and r-process.