Roles of nuclear weak rates on the evolution of degenerate cores in stars

Suzuki, Toshio; Tsunodaa, Naofumi; Tsunoda, Yuhsuke; Shimizu, Noritaka; Otsuka, Takaharu

doi:10.1051/epjconf/201716501048

Cited by 3 publications

(2 citation statements)

References 26 publications

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“…This situation is improved by using an effective interaction in sd-pf shell obtained by the extended Kuo-Krenciglowa (EKK) method [98,100], which is free from the divergence problem in G-matrix calculations in two-major shells [101]. Thus the transitions between the low-lying states of 31 Mg and 31 Al are of GT-type, which leads to cooling by the nuclear Urca process [102].…”

Section: Discussionmentioning

confidence: 99%

Nuclear Weak Rates and Nuclear Weak Processes in Stars

Suzuki

2022

Preprint

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Nuclear weak rates in stellar environments are obtained by taking into account recent advances in shell-model studies of spin-dependent excitation modes in nuclei including Gamow-Teller (GT) and spin-dipole transitions. They are applied to nuclear weak processes in stars such as cooling and heating of the cores of stars and nucleosynthesis in supernovae. The important roles of accurate weak rates for the study of astrophysical processes are pointed out in the following cases. (1) The electron-capture (e-capture) and β-decay rates in sd-shell are evaluated with the USDB Hamiltonian and used to study the evolution of O-Ne-Mg cores in stars with 8-10 M ⊙ . The important roles of the A =23 and 25 pairs of nuclei for the cooling of the cores by nuclear Urca processes are investigated. (2) They are also used to study heating of the O-Ne-Mg core by double e-captures on 20 Ne in later stages of the evolution. Especially, the e-capture rates for a second-forbidden transition in 20 Ne are evaluated with the multipole expansion method by Walecka as well as the method of Behrens-Bühring. Possible important roles of the transition in heating the O-Ne-Mg cores and implications on the final fate of the cores (core-collapse or thermonuclear explosion) are discussed.(3) The weak rates in pf -shell nuclei are evaluated with a new Hamiltonian, GXPF1J, and applied to nucleosynthesis of iron-group elements in Type Ia supernova explosions. The over-production problem of neutron-rich iron isotopes compared with the solar abundances, which remained for the rates according to Fuller, Fowler and Newman, is much improved, and the over-production is now reduced to be within a factor of two. (4) The weak rates for nuclei with two-major shells are evaluated. For sd-pf shell in the island of inversion, the weak rates for the A=31 pair of nuclei, which are important for nuclear Urca processes in neutron-star crusts, are evaluated with the effective interaction obtained by the extended Kuo-Krenciglowa (EKK) method. Neutron-rich nuclei with and near neutron number (N ) of 50 are important for core-collapse processes in supernova explosions. The transition strengths and e-capture rates in 78 Ni are evaluated with a new shell-model Hamiltonian for the pf -sdg shell, and compared with those obtained by the randomphase-approximation (RPA) and an effective rate formula. (5) β-decay rates and half-lives of N =126 isotones, the waiting point nuclei for r-process nucleosynthesis, are evaluated by shell-model calculations with both the GT and first-forbidden transitions. The important roles of the forbidden transitions are pointed out for the isotones with larger proton number (Z). The half-lives are found to be shorter than those obtained by standard models such as the finite-range droplet model (FRDM) by Möller. (6) Neutrino-nucleus reaction cross sections on 13 C, 16 O and 40 Ar are obtained with new shell-model Hamiltonians. Implications on nucleosynthesis, neutrino detection, neutrino oscillations and neutrino mass hierarchy are discussed.

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Section: Discussionmentioning

confidence: 99%

Nuclear Weak Rates and Nuclear Weak Processes in Stars

Suzuki

2022

Preprint

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“…Large admixtures of pf-shell components with both 2p-2h and 4p-4h excitations are found in 32 Mg, and energy spectra in 31 Mg are well reproduced; the ground state is 1/2 + consistent with the observation. The weak rates for the 31 Mg-31 Al pair, which are important for the URCA process in neutron star crusts [14], are evaluated, and the URCA density is assigned to be at log 10 (ρY e ) =10.14 [15].…”

Section: Sd-pf Shell In the Island Of Inversionmentioning

confidence: 99%

Nuclear Weak Rates for Astrophysical Processes in Stars

Suzuki

Chiba

Yoshida

et al. 2020

Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15)

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We have updated nuclear weak rates relevant to the study of astrophysical processes in stars. Neutrino-induced reaction cross sections, electron-capture and β-decay rates at stellar environments are obtained with new shell-model Hamiltonians that prove to be successful in describing spin responses-Gamow-Teller and spin-dipole transitions-in nuclei. The cross sections and rates are applied to nucleosynthesis in supernovae, detection of νand nuclear URCA processes.

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Nuclear weak rates and nuclear weak processes in stars

Suzuki

2022

Progress in Particle and Nuclear Physics

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Roles of nuclear weak rates on the evolution of degenerate cores in stars

Cited by 3 publications

References 26 publications

Nuclear Weak Rates and Nuclear Weak Processes in Stars

Nuclear Weak Rates and Nuclear Weak Processes in Stars

Nuclear Weak Rates for Astrophysical Processes in Stars

Nuclear weak rates and nuclear weak processes in stars

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