2025-12-05 中国科学院（CAS）
Figure 1. The mass abundance distribution map at 100 seconds after the start of the rp-process. (Image from IMP)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/phys/202512/t20251205_1135193.shtml
- https://iopscience.iop.org/article/10.3847/1538-4357/ae1470
恒星X線バーストにおける26Pと27Sの精密質量測定と26P ( p , γ ) 27S反応への影響 Precision Mass Measurement of 26P and 27S and Their Impact on the 26P(p,γ)27S Reaction in Stellar X-Ray Bursts
Z. Y. Chen, X. L. Yan, S. Q. Hou, J. B. Liu, J. Y. Shi, X. H. Zhou, Y. H. Zhang, M. Wang, X. Zhou, M. Zhang,…
The Astrophysical Journal Published: 2025 December 1
DOI:10.3847/1538-4357/ae1470
Abstract
Based on the experimental Cooler Storage Ring in Lanzhou, we directly determined the masses of 27S and 26P using Bρ-defined isochronous mass spectrometry. The mass excesses were determined to be 17,437(24) keV for 27S and 10,997(10) keV for 26P. These values yield a proton separation energy of 849(26) keV for 27S, representing an eightfold precision improvement over the previous one of 581(214) keV. With precisely measured masses, we evaluated the thermonuclear 26P(p, γ)27S reaction rate under X-ray burst conditions. The updated rate is enhanced within the 0.4–2 GK temperature range, reaching up to 5 times the previous rate at 1 GK. The uncertainty of the reverse 27S(γ, p)26P reaction rate is drastically reduced with the new high-precision mass results, from over 10 orders of magnitude to less than one. We further assessed the impact of the revised rates on the nucleosynthesis in Type I X-ray bursts using a one-zone postprocessing model. The results show that the final abundance ratio of 27S to 26P is increased by about 1 order of magnitude, indicating a more efficient reaction flow toward 27S. Although the sequence 25Si(p, γ)26P(p, γ)27S(β+)27P is not on the main rp-process path, it emerges as a nonnegligible branch contributing to 27P synthesis.
