Modification of the Brink-Axel Hypothesis for High Temperature Nuclear Weak Interactions

Abstract

We present shell model calculations of electron capture strength distributions in A=28 nuclei and computations of the corresponding capture rates in supernova core conditions. We find that in these nuclei the Brink-Axel hypothesis for the distribution of Gamow-Teller strength fails at low and moderate initial excitation energy, but may be a valid tool at high excitation. The redistribution of GT strength at high initial excitation may affect capture rates during collapse. If these trends which we have found in lighter nuclei also apply for the heavier nuclei which provide the principal channels for neutronization during stellar collapse, then there could be two implications for supernova core electron capture physics. First, a modified Brink-Axel hypothesis could be a valid approximation for use in collapse codes. Second, the electron capture strength may be moved down significantly in transition energy, which would likely have the effect of increasing the overall electron capture rate during stellar collapse.

15 pages, 19 figures

References in corpus (7)

• Pulsar spins from an instability in the accretion shock of supernovae
• Nucleosynthesis-relevant conditions in neutrino-driven supernova outflows. I. Spherically symmetric hydrodynamic simulations
• Multidimensional supernova simulations with approximative neutrino transport. II. Convection and the advective-acoustic cycle in the supernova core
• Stellar electron-capture rates in pf-shell nuclei from quasiparticle random-phase approximation calculations
• Comparative study of Gamow-Teller strength distributions in the odd-odd nucleus 50V and its impact on electron capture rates in astrophysical environments
• Nickel isotopes in stellar matter
• Neutrino cooling rates due to ${}^{54,55,56}$Fe for presupernova evolution of massive stars

Cited by in corpus (13)

• Impact of New Gamow-Teller Strengths on Explosive Type Ia Supernova Nucleosynthesis
• Sensitivity of Type Ia supernovae to electron capture rates
• Nuclear level densities and $\gamma$-ray strength functions in ${}^{120,124}$Sn isotopes: impact of Porter-Thomas fluctuations
• Nuclear neutrino energy spectra in high temperature astrophysical environments
• New experimental constraint on the ${}^{185}$W($n,\gamma$)${}^{186}$W cross section
• Neutrino Spectra from Nuclear Weak Interactions in $sd$-Shell Nuclei Under Astrophysical Conditions
• Gamow-Teller strength and lepton captures rates on 66-71Ni in stellar matter
• Validity of Brink Axel Hypothesis for calculations of allowed stellar weak rates of heavy nuclei
• Impact of the Brink Axel Hypothesis on Unique First Forbidden \b{eta} transitions for r process nuclei
• Lepton capture rates due to isotopes of vanadium in astrophysical environment
• Gamow-Teller strength distributions and stellar weak-interaction rates for ${}^{76}$Ge and ${}^{82}$Se using the deformed pn-QRPA model
• Neutrino cooling rates due to nickel isotopes for presupernova evolution of massive stars
• Stellar ${\beta }^{-}$-decay rate of ${}^{63}$Ni and its impact on the $s$-process nucleosynthesis in massive stars