Sensitivity of Type Ia supernovae to electron capture rates

E.T.S. Arquitectura del Vallès, Universitat Politècnica de Catalunya, Carrer Pere Serra 1-15, 08173 Sant Cugat del Vallès, Spain
e-mail: eduardo.bravo@upc.edu

Received: 22 January 2019
Accepted: 8 March 2019

Abstract

The thermonuclear explosion of massive white dwarfs is believed to explain at least a fraction of Type Ia supernovae (SNIa). After thermal runaway, electron captures on the ashes left behind by the burning front determine a loss of pressure, which impacts the dynamics of the explosion and the neutron excess of matter. Indeed, overproduction of neutron-rich species such as ⁵⁴Cr has been deemed a problem of Chandrasekhar-mass models of SNIa for a long time. I present the results of a sensitivity study of SNIa models to the rates of weak interactions, which have been incorporated directly into the hydrodynamic explosion code. The weak rates have been scaled up or down by a factor ten, either globally for a common bibliographical source, or individually for selected isotopes. In line with previous works, the impact of weak rates uncertainties on sub-Chandrasekhar models of SNIa is almost negligible. The impact on the dynamics of Chandrasekhar-mass models and on the yield of ⁵⁶Ni is also scarce. The strongest effect is found on the nucleosynthesis of neutron-rich nuclei, such as ⁴⁸Ca, ⁵⁴Cr, ⁵⁸Fe, and ⁶⁴Ni. The species with the highest influence on nucleosynthesis do not coincide with the isotopes that contribute most to the neutronization of matter. Among the latter, there are protons, ^54, 55Fe, ⁵⁵Co, and ⁵⁶Ni, while the main influencers are ^54, 55Mn and ^{55 − 57}Fe, in disagreement with Parikh et al (2013, A&A, 557, A3), who found that SNIa nucleosynthesis is most sensitive to the β⁺-decay rates of ²⁸Si, ³²S, and ³⁶Ar. An increase in all weak rates on pf-shell nuclei would affect the dynamical evolution of burning bubbles at the beginning of the explosion and the yields of SNIa.