Mass measurements show slowdown of rapid proton capture process at waiting-point nucleus 64 Ge

X. Zhou,M. Wang,Y. H. Zhang, Yu. A. Litvinov,Z. Meisel,K. Blaum,X. H. Zhou, S. Q. Hou,K. A. Li,H. S. Xu, R. J. Chen,H. Y. Deng,C. Y. Fu, W. W. Ge,J. J. He,W. J. Huang, H. Y. Jiao,H. F. Li,J. G. Li, T. Liao,S. A. Litvinov,M. L. Liu,Y. F. Niu, P. Shuai,J. Y. Shi,Y. N. Song, M. Z. Sun,Q. Wang, Y. M. Xing,X. Xu,F. R. Xu, X. L. Yan,J. C. Yang,Y. Yu, Q. Yuan, Y. J. Yuan,Q. Zeng,M. Zhang,S. Zhang

Nature Physics(2023)

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摘要
X-ray bursts are among the brightest stellar objects frequently observed in the sky by space-based telescopes. A type-I X-ray burst is understood as a violent thermonuclear explosion on the surface of a neutron star, accreting matter from a companion star in a binary system. The bursts are powered by a nuclear reaction sequence known as the rapid proton capture process (rp process), which involves hundreds of exotic neutron-deficient nuclides. At so-called waiting-point nuclides, the process stalls until a slower β + decay enables a bypass. One of the handful of rp process waiting-point nuclides is 64 Ge, which plays a decisive role in matter flow and therefore the produced X-ray flux. Here we report precision measurements of the masses of 63 Ge, 64,65 As and 66,67 Se—the relevant nuclear masses around the waiting-point 64 Ge—and use them as inputs for X-ray burst model calculations. We obtain the X-ray burst light curve to constrain the neutron-star compactness, and suggest that the distance to the X-ray burster GS 1826–24 needs to be increased by about 6.5% to match astronomical observations. The nucleosynthesis results affect the thermal structure of accreting neutron stars, which will subsequently modify the calculations of associated observables.
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rapid proton capture process,nucleus,mass,waiting-point
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