Did Hypernova Explosions of the First Generation Stars Produce the Chemical Peculiarity of the Objects in Early Universe?

宇宙中的第一代恒星被称为第三族恒星，它们不包含重元素。在这项研究中，我们试图从极端贫金属星(EMP)的核合成和化学丰度之间的比较来研究它们的性质。我们重点研究了EMP恒星的特殊丰度模式，特别是斯巴鲁望远镜发现的金属丰度仅低于5个数量级的超贫金属星(HMP)。这颗HMP星有极大的C/Fe，但也有很大的(Na，Mg，Al)/Fe。这种丰度模式可能源于Pop III恒星的核合成。在这项研究中，我们将我们对Pop III恒星核合成的研究扩展到非球面爆炸模型。1)在HMP/EMP星中，发现了许多(C，N)/Fe比值较大的富碳、富氮恒星。2)富碳HMP/EMP星之间(Na，Mg，Al)/Fe的变化可以用混合机制和后退机制以及对爆炸能量的依赖来解释。3)在球面模型中，相对较低的能量爆炸实现了较大的后退。4)在双极爆炸中，自然地诱发了类似混合-后退的事件，从而使超新星爆炸模型能够工作。

The first generation of stars, called Population III stars, in the Universe do not contain heavy elements. In this study, we tried to investigate their nature from the comparison between nucleosynthesis and the chemical abundances of extremely metal-poor (EMP) stars. We focus on the peculiar abundance pattern of EMP stars, in particular, those of the hyper metal-poor (HMP) star discovered by SUBARU telescope, whose, metallicity is only less than 5 orders of magnitude. This HMP star has extremely large C/Fe but also large (Na,Mg,Al)/Fe. Such an abundance pattern may stem from nucleosynthesis in Pop III stars.In this study, we extended our study of nucleosynthesis in Pop III stars to the aspherical explosion models. Our findings are summarized as follows :1) Among the HMP/EMP stars, many C and N-rich stars with quite large ratios of (C,N)/Fe have been discovered. We showed that such large ratios can be explained with the black-hole-forming supernovae.2) Variations of (Na,Mg,Al)/Fe among the C-rich HMP/EMP stars can be explained with the mixing and the fallback mechanism, and the dependence on the explosion energy.3) In spherical models, large fallback is realized in the relatively low energy explosions.4) In bipolar explosions, the mixing-fallback like events are naturally induced, so that hypernova explosion model can work.