分类： 天文学 >> 恒星和银河系 提交时间： 2023-12-31
Hong-Liang Yan
Jian-Rong Shi
Yu-Tao Zhou
Yong-Shou Chen
Er-Tao Li
Suyalatu Zhang
Shao-Lan Bi
Ya-Qian Wu
Zhi-Hong Li
Bing Guo
Wei-Ping Liu
Qi Gao
Jun-Bo Zhang
Ze-Ming Zhou
Hai-Ning Li
Gang Zhao
摘要： About 1% of giants have anomalously high Li abundances in their atmospheres, conflicting directly with the prediction of the standard stellar evolution models. This finding makes the production and evolution of Li in the Universe intriguing, not only in the sense of Big Bang nucleosynthesis or the interstellar medium, but also for the evolution of stars. Decades of efforts have been put into explaining why such extreme objects exist, yet the origins of Lirich giants are still being debated. Here we report the discovery of the most Li-rich giant known to date, with a very high Li abundance of 4.51. This rare phenomenon was observed coincidentally with another short-term event: the star is experiencing its luminosity bump on the red giant branch. Such a high Li abundance indicates that the star might be at the very beginning of its Li-rich phase, which provides a great opportunity to investigate the origin and evolution of Li in the Galaxy. A detailed nuclear simulation is presented with up-to-date reaction rates to recreate the Li enrichment process in this star. Our results provide tight constraints on both observational and theoretical points of view, suggesting that low-mass giants can internally produce Li to a very high level through 7Be transportation during the red giant phase.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Liyong Zhang
Jianjun He
Richard J. deBoer
Michael Wiescher
Alexander Heger
Daid Kahl
Jun Su
Daniel Odell
Yinji Chen
Xinyue Li
Jianguo Wang
Long Zhang
Fuqiang Cao
Hao Zhang
Zhicheng Zhang
Xinzhi Jiang
Luohuan Wang
Ziming Li
Luyang Song
Hongwei Zhao
摘要： The origin of calcium production in the first stars (Pop III stars), which formed out of the primordial matter of the Big Bang, and their fates, remain most fascinating mysteries in astrophysics. Advanced nuclear burning and supernovae were thought to be the dominant source of the Ca production seen in all stars. Here we report on a qualitatively different path to Ca production through break-out from the "warm" carbon-nitrogen-oxygen (CNO) cycle. We extend direct measurement of the $^{19}$F($p$, $\gamma$)$^{20}$Ne break-out reaction down to an unprecedentedly low energy point of 186 keV and discover a key resonance at 225 keV. In the domain of astrophysical interest, at around 0.1 giga kelvin, this thermonuclear $^{19}$F($p$,$\gamma$)$^{20}$Ne rate is up to a factor of 7.4 larger than the previous recommended rate. Our stellar models show a stronger break-out during stellar hydrogen burning than thought before, and may reveal the nature of Ca production in Pop III stars imprinted on the oldest known ultra-iron poor star, SMSS0313-6708. This result from the China Jinping Underground Laboratory, the deepest laboratory in the world, offering an environment with extremely low cosmic-ray induced background, has far-reaching implications on our understanding of how the first stars evolve and die. Our rate showcases the impact that faint Pop III star supernovae can have on the nucleosynthesis observed in the oldest known stars and first galaxies, key mission targets of the James Webb Space Telescope.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Liyong Zhang
Jianjun He
Richard J. deBoer
Michael Wiescher
Alexander Heger
Daid Kahl
Jun Su
Daniel Odell
Yinji Chen
Xinyue Li
Jianguo Wang
Long Zhang
Fuqiang Cao
Hao Zhang
Zhicheng Zhang
Xinzhi Jiang
Luohuan Wang
Ziming Li
Luyang Song
Hongwei Zhao
摘要： The origin of calcium production in the first stars (Pop III stars), which formed out of the primordial matter of the Big Bang, and their fates, remain most fascinating mysteries in astrophysics. Advanced nuclear burning and supernovae were thought to be the dominant source of the Ca production seen in all stars. Here we report on a qualitatively different path to Ca production through break-out from the "warm" carbon-nitrogen-oxygen (CNO) cycle. We extend direct measurement of the $^{19}$F($p$, $\gamma$)$^{20}$Ne break-out reaction down to an unprecedentedly low energy point of 186 keV and discover a key resonance at 225 keV. In the domain of astrophysical interest, at around 0.1 giga kelvin, this thermonuclear $^{19}$F($p$,$\gamma$)$^{20}$Ne rate is up to a factor of 7.4 larger than the previous recommended rate. Our stellar models show a stronger break-out during stellar hydrogen burning than thought before, and may reveal the nature of Ca production in Pop III stars imprinted on the oldest known ultra-iron poor star, SMSS0313-6708. This result from the China Jinping Underground Laboratory, the deepest laboratory in the world, offering an environment with extremely low cosmic-ray induced background, has far-reaching implications on our understanding of how the first stars evolve and die. Our rate showcases the impact that faint Pop III star supernovae can have on the nucleosynthesis observed in the oldest known stars and first galaxies, key mission targets of the James Webb Space Telescope.
点击量
通过
点击量
下载量
评论
待评议
