2019 Fiscal Year Final Research Report
Cosmic Radioactivity and Origin of R-process Elements toward Solar System Formation
| Project/Area Number |
17K05459
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | National Astronomical Observatory of Japan |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | ｒ過程元素 / 超新星 / 中性子星連星系合体 / コラプサー / 銀河化学進化 / 太陽系形成 / ニュートリノ / アイソトープ |
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| Outline of Final Research Achievements |
We found that 98Tc (halflife t=4.2x10^6 years) which existed at the epoch of the solar system formation was synthesized in the neutrino-process in the gravitational core-collapse supernovae. 129I is produced mainly in supernovae, and actinides like 244Pu are produced in both magnetohydrodynamic jet supernovae and binary neutron-star mergers. From our theoretical calculations of the galactic chemical evolution of r-process elements, r-process elements in metal-deficient halo stars which are the early generations of stars having [Fe/H] < -2, were mainly produced in supernovae and collapsars, while there was little contribution from the binary neutron-star mergers due to merger time-delay by at least 100 My. We found that merger contribution has started later when the metallicity becomes as large as [Fe/H]>-1 in relatively recent epoch along cosmic evolution history.
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| Free Research Field |
宇宙物理学
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| Academic Significance and Societal Importance of the Research Achievements |
長寿命放射性重元素（ｒ過程元素）の起源は、米国科学アカデミーが取り上げた現代物理学における１１の謎の一つに上げられた研究課題である。当科研費研究において、宇宙での爆発的元素合成に関する天文学・素粒子物理学・原子核物理学分野の専門的知見を持ち寄って、ｒ過程元素の起源を明らかにする学際的研究を展開した。超新星・コラプサー・中性子星連星系合体等全ての起源候補天体でのｒ元素合成を研究し、初期宇宙から太陽系形成期までの元素組成の宇宙時間的進化の解明を目指した。超新星ニュートリノ元素合成および振動現象の新たな役割等の発見があり、科学論文として発表するとともに、記者発表を行って研究成果の社会還元に努めた。
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