Sensitivity of Type Ia supernovae to electron capture rates

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 $^{54}$Cr 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/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 $^{56}$Ni is also scarce. The strongest effect is found on the nucleosynthesis of neutron-rich nuclei, such as $^{48}$Ca, $^{54}$Cr, $^{58}$Fe, and $^{64}$Ni. The species with the highest influence on nucleosynthesis do not coincide with the isotopes that contribute most to the neutronization of matter. Among the last ones, there are protons, $^{54,55}$Fe, $^{55}$Co, and $^{56}$Ni, while the main influencers are $^{54,55}$Mn and $^{55-57}$Fe, in disagreement with Parikh et al (2013), who found that SNIa nucleosynthesis is most sensitive to the $β^+$-decay rates of $^{28}$Si, $^{32}$S, and $^{36}$Ar. An eventual increase in all weak rates on pf-shell nuclei would affect the dynamical evolution of hot bubbles, running away at the beginning of the explosion, and the yields of SNIa.