Journal Article

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

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

2023

Overview

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 64Ge, which plays a decisive role in matter flow and therefore the produced X-ray flux. Here we report precision measurements of the masses of 63Ge, 64,65As and 66,67Se—the relevant nuclear masses around the waiting-point 64Ge—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.Rapid proton capture nucleosynthesis stalls at waiting-point nuclides, including 64Ge. Precision mass measurements in the vicinity of this nuclide influence state-of-the-art calculations of X-ray bursts from accreting neutron stars.

• Publisher: Nature Publishing Group
• Subject: Binary stars / Bursts / Celestial bodies / Companion stars / Deposition / Light curve / Neutron stars / Neutrons / Nuclear fusion / Nuclear reactions / Nuclides / Protons / Spaceborne telescopes / Stars / Thermonuclear explosions