Forbidden electron capture on $^{24}$Na and $^{27}$Al in degenerate oxygen-neon cores - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Phys.Rev.C Année : 2022

Forbidden electron capture on $^{24}$Na and $^{27}$Al in degenerate oxygen-neon cores

D.F. Strömberg
  • Fonction : Auteur
G. Martínez-Pinedo
  • Fonction : Auteur

Résumé

Background: Stars with an initial mass of 7–11 solar masses form degenerate oxygen-neon cores following carbon burning. Electron captures in such cores can trigger runaway oxygen burning, resulting in either a collapse or a thermonuclear explosion. Previous work constrained the contribution of the forbidden 0g.s.+2g.s.+ transition to the Ne20(e,νe)F20 rate and discussed its significance for the evolution of the core. Purpose: We provide a detailed description of the formalism used in previous work and apply it to two further forbidden transitions that are relevant to degenerate oxygen-neon cores: the 4g.s.+21+ transition in Na24(e,νe)Ne24 and the 5/2g.s.+1/2g.s.+ transition in Al27(e,νe)Mg27. Method: The relevant nuclear matrix elements are determined through shell model calculations and constraints from the conserved vector current (CVC) theory. We then investigate the astrophysical impact using the stellar evolution code mesa (Modules for Experiment in Stellar Astrophysics) and through timescale arguments. Results: In the relevant temperature range, the forbidden transitions substantially reduce the threshold densities for Na24(e,νe)Ne24 and Al27(e,νe)Mg27. In the mesa models, Na24(e,νe)Ne24 now occurs immediately following the onset of Mg24(e,νe)Na24. The impact on the overall evolution is uncertain; this is due to known difficulties in accounting for convective instabilities triggered by the A=24 electron captures. The transition between Al27 and Mg27 may have a minor effect on the early evolution but is unlikely to affect the outcome. Conclusions: The studied transitions should be included when calculating weak interaction rates between Na24 and Ne24 for temperatures log10(T[K])8.5 and between Al27 and Mg27 for log10(T[K])8.8.

Dates et versions

hal-03203631 , version 1 (20-04-2021)

Identifiants

Citer

D.F. Strömberg, G. Martínez-Pinedo, F. Nowacki. Forbidden electron capture on $^{24}$Na and $^{27}$Al in degenerate oxygen-neon cores. Phys.Rev.C, 2022, 105 (2), pp.025803. ⟨10.1103/PhysRevC.105.025803⟩. ⟨hal-03203631⟩
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