However, explosion of WDs more massive than ∼1 M ⊙ may drive the central regions to densities and temperatures high enough that the electron mole number changes significantly. 2018) are not expected to be affected by either electron captures or beta-decays during the pre-explosive or explosive phases. On the other hand, SNIa coming from the explosion of sub-Chandrasekhar mass WDs ( Woosley & Weaver 1994 Fink et al.
Early during the explosion, electron captures on IGN reduce the electron pressure and affect the dynamical evolution and the nucleosynthesis of SNIa. In SNIa triggered by the explosion of massive WDs, first, during the pre-supernova carbon simmering phase, electron captures and beta decays drive the equilibrium configuration of the star in response to mass accretion from a companion star later, electron captures destabilize the WD and start the dynamical phase of the explosion (e.g. 2019, to cite only a few), there are indications that SNIa may be produced by a combination of all of them (e.g. While all of these scenarios have several points in favour and against ( Chomiuk et al. Nowadays, there is debate about the nature of SNIa progenitors, whether they are more or less massive white dwarfs (WD), and whether they are part of a single degenerate or a double degenerate binary system. The relevance of weak interactions for Type Ia supernovae (SNIa) depends on the progenitor system. 2018, for a recent review) are predicted to be triggered by the transmutation of the late nucleosinthetic products of the most massive intermediate-mass stars with low metallicity progenitors ( Miyaji et al. As another example, electron capture supernovae (see Gil-Pons et al. These nuclei were subsequently targets of theoretical studies to refine the associated weak rates. (1994) studied the most relevant electron captures in the pre-supernova evolution of massive stars, and identified many IGN that may have an influence on the conditions at supernova core collapse. 1990), and leave an imprint on the nucleosynthetic yield of the innermost ejected shells ( Langanke et al. In Type II supernovae first electron captures in the iron core reduce the pressure and start the collapse and, later, beta-decays on neutron-rich nuclei contribute appreciably to the neutrino flux, help to regulate the core temperature ( Aufderheide et al. Weak interactions on iron-group nuclei (IGN) play a key role in the late stages of stellar evolution. Key words: nuclear reactions / nucleosynthesis / abundances / supernovae: general / white dwarfs 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. Among the latter, there are protons, 54, 55Fe, 55Co, and 56Ni, while the main influencers are 54, 55Mn and 55 − 57Fe, 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. The species with the highest influence on nucleosynthesis do not coincide with the isotopes that contribute most to the neutronization of matter. The strongest effect is found on the nucleosynthesis of neutron-rich nuclei, such as 48Ca, 54Cr, 58Fe, and 64Ni. The impact on the dynamics of Chandrasekhar-mass models and on the yield of 56Ni is also scarce.
In line with previous works, the impact of weak rates uncertainties on sub-Chandrasekhar models of SNIa is almost negligible. 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. 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. Indeed, overproduction of neutron-rich species such as 54Cr has been deemed a problem of Chandrasekhar-mass models of SNIa for a long time. 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. Arquitectura del Vallès, Universitat Politècnica de Catalunya, Carrer Pere Serra 1-15, 08173 Sant Cugat del Vallès, SpainĮ-mail: thermonuclear explosion of massive white dwarfs is believed to explain at least a fraction of Type Ia supernovae (SNIa).
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