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Journal Article

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


Blaum,  K.
Division Prof. Dr. Klaus Blaum, MPI for Nuclear Physics, Max Planck Society;

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Zhou, X., Wang, M., Zhang, Y. H., Litvinov, Y. A., Meisel, Z., Blaum, K., et al. (2023). Mass measurements show slowdown of rapid proton capture process at waiting-point nucleus 64Ge. Nature Physics. doi:10.1038/s41567-023-02034-2.

Cite as: https://hdl.handle.net/21.11116/0000-000D-0DC1-B
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.