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arXiv 1405.6340astro-ph.HEastro-ph.SR
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低红移对不稳定性超新星的爆发与核合成

Explosion and nucleosynthesis of low redshift pair instability supernovae

Alexandra Kozyreva, Sung-Chul Yoon, Norbert Langer

摘要:

最近的观测和恒星演化模型都表明,在本宇宙中可能发生对不稳定超新星(PISNe),其金属丰度低于Z_Sun/3。以前的PISN模型大多是在早期宇宙的背景下在非常低的金属丰度下产生的。我们提出了新的PISNe模型在Z=0.001的金属丰度,这是相关的本地宇宙。我们采用Langer et al.(2007)提出的初始质量为150和250太阳质量、金属丰度为Z=0.001的对不稳定祖先的自洽恒星演化模型,并使用包含200种同位素的广泛核网络的流体力学恒星演化代码,跟踪这些模型在超新星爆炸中的演化。两种模型都以PISNe的形式爆炸,而不会留下致密的恒星残骸。我们的模型产生的核合成模式,一般是类似于人口III PISN模型,其主要特点是生产大量的α-元素和强烈缺乏的奇数电荷的元素。然而,我们模型中的奇偶效应明显弱于人口III模型中的奇偶效应。与核心坍缩超新星在类似的金属丰度(Z=0.002)的核合成产率的比较表明,PISNe可能强烈影响Z=0.002以下的化学演化,假设一个标准的初始质量函数。奇偶效应预计是最突出的硅和钙之间的中间质量元素。随着未来对星族II恒星化学丰度的观测,我们的结果可以用来限制我们银河系过去演化过程中发生的PISNe的数量。

英文摘要:

Both recent observations and stellar evolution models suggest that pair-instability supernovae (PISNe) could occur in the local Universe, at metallicities below Z_Sun/3. Previous PISN models were mostly produced at very low metallicities in the context of the early Universe. We present new PISNe models at a metallicity of Z=0.001, which are relevant for the local Universe. We take the self-consistent stellar evolutionary models of pair-instability progenitors with initial masses of 150 and 250 solar masses at metallicity of Z=0.001 by Langer et al. (2007) and follow the evolution of these models through the supernova explosions, using a hydrodynamics stellar evolution code with an extensive nuclear network including 200 isotopes. Both models explode as PISNe without leaving a compact stellar remnant. Our models produce a nucleosynthetic pattern that is generally similar to that of Population III PISN models, which is mainly characterized by the production of large amounts of alpha-elements and a strong deficiency of the odd-charged elements. However, the odd-even effect in our models is significantly weaker than that found in Population III models. The comparison with the nucleosynthetic yields from core-collapse supernovae at a similar metallicity (Z=0.002) indicates that PISNe could have strongly influenced the chemical evolution below Z=0.002, assuming a standard initial mass function. The odd-even effect is predicted to be most prominent for the intermediate mass elements between silicon and calcium. With future observations of chemical abundances in Population II stars, our result can be used to constrain the number of PISNe that occurred during the past evolution of our Galaxy.

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