The Regulated NiCu Cycles with the new Cu(p,)Zn reaction rate and the Influence on Type-I X-Ray Bursts: GS 182624 Clocked Burster
arXiv:2107.11552 · doi:10.3847/1538-4357/ac4d89
Abstract
During the X-ray bursts of GS 182624, "clocked burster", the nuclear reaction flow that surges through the rapid-proton capture process path has to pass through the NiCu cycles before reaching the ZnGa cycles that moderate the further extent of hydrogen burning in the region above germanium and selenium isotopes. The Cu(p,)Zn reaction located in the NiCu cycles plays an important role in influencing the burst light curves as found by Cyburt et al. (2016). We deduce the Cu(p,)Zn reaction rate based on the experimentally determined important nuclear structure information, isobaric-multiplet-mass equation, and large-scale shell model calculations. Based on the isobaric-multiplet-mass equation, we propose a possible order of and dominant resonance states and constrain the resonance energy of the state. The latter reduces the contribution of the dominant resonance state. The new reaction rate is up to a factor of four lower than the Forstner et al. (2001) rate recommended by JINA REACLIB v2.2 at the temperature regime sensitive to clocked bursts of GS 182624. Using the simulation from the one-dimensional implicit hydrodynamic code, KEPLER, to model the thermonuclear X-ray bursts of GS 182624 clocked burster, we find that the new Cu(p,)Zn coupled with the latest Ni(p,)Cu and Ni(p,)Cu reaction rates redistributes the reaction flow in the NiCu cycles and strongly influences the burst ash composition, whereas the Cu(p,)Ni and Cu(p,)Zn reactions suppress the influence of the Cu(p,)Zn reaction and diminish the impact of nuclear reaction flow that by-passes the important Ni waiting point induced by the Ni(p,)Cu reaction on burst light curve.
arXiv comment18 pages, 10 figures, 6 tables, accepted by The Astrophysical Journal on 14 January 2022
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