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

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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.