Abstract During the Xray bursts of GS 1826−24, a “clocked burster”, the nuclear reaction flow that surges through the rapidproton capture process path has to pass through the NiCu cycles before reaching the ZnGa cycles that moderate further hydrogen burning in the region above the germanium and selenium isotopes. The 57 Cu(p, γ ) 58 Zn reaction that occurs in the NiCu cycles plays an important role in influencing the burst light curves found by Cyburt et al. We deduce the 57 Cu(p, γ ) 58 Zn reaction rate based on the experimentally determined important nuclear structure information, isobaricmultipletmass equation, and largescale shellmodel calculations. Based on the isobaricmultipletmass equation, we propose a possible order of 1 1 +  and 2 3 + dominant resonance states and constrain the resonance energy of the 1 2 + state. The latter reduces the contribution of the 1 2 + dominant resonance state. The new reaction rate is up to a factor of 4 lower than the Forstner et al. rate recommended by JINA REACLIB v2.2 at the temperature regime sensitive to clocked bursts of GS 1826−24. Using the simulation from the onedimensional implicit hydrodynamic code K epler to model the thermonuclear Xray bursts of the GS 1826−24 clocked burster, we find that the new 57 Cu(p, γ ) 58 Zn reaction rate, coupled with the latest 56 Ni(p, γ ) 57 Cu and 55 Ni(p, γ ) 56 Cu reaction rates, redistributes the reaction flow in the NiCu cycles and strongly influences the burst ash composition, whereas the 59 Cu(p, α ) 56 Ni and 59 Cu(p, γ ) 60 Zn reactions suppress the influence of the 57 Cu(p, γ ) 58 Zn reaction and diminish the impact of nuclear reaction flow that bypasses the important 56 Ni waiting point induced by the 55 Ni(p, γ ) 56 Cu reaction on the burst light curve.
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Nuclear reaction network unveils novel reaction patterns based on stellar energies
Abstract Despite the advances in discovering new nuclei, modeling microscopic nuclear structure, nuclear reactors, and stellar nucleosynthesis, we still lack a systemic tool, such as a network approach, to understand the structure and dynamics of over 70 thousands reactions compiled in JINA REACLIB. To this end, we develop an analysis framework, under which it is simple to know which reactions generally are possible and which are not, by counting neutrons and protons incoming to and outgoing from any target nucleus. Specifically, we assemble here a nuclear reaction network in which a node represents a nuclide, and a link represents a direct reaction between nuclides. Interestingly, the degree distribution of nuclear network exhibits a bimodal distribution that significantly deviates from the common powerlaw distribution of scalefree networks and Poisson distribution of random networks. Based on the dynamics from the cross section parameterizations in REACLIB, we surprisingly find that the distribution is universal for reactions with a rate below the threshold, λ < e − T γ , where T is the temperature and γ ≈ 1.05. Moreover, we discover three rules that govern the structure pattern of nuclear reaction network: (i) reactiontype is determined by linking choices, (ii) network distances between the reacting nuclides on 2D grid of Z vs N of nuclides are short, and (iii) each node in and outdegrees are close to each other. By incorporating these three rules, our model universally unveils the underlying nuclear reaction patterns hidden in a large and dense nuclear reaction network regardless of nuclide chart expansions. It enables us to predict missing links that represent possible new nuclear reactions not yet discovered.
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 Award ID(s):
 2047488
 NSFPAR ID:
 10316719
 Date Published:
 Journal Name:
 New Journal of Physics
 Volume:
 23
 Issue:
 8
 ISSN:
 13672630
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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