Evolution of onemg core in super-agb stars toward electron-capture supernovae: Effects of updated electron-capture rate

Stars with ∼8-10 M _o˙ evolve to form a strongly degenerate ONeMg core. When the core mass becomes close to the Chandrasekhar mass, the core undergoes electron captures on ²⁴Mg and ²⁰Ne that induce an electron-capture supernova (ECSN). In order to clarify whether the ECSN leads to a collapse or thermonuclear explosion, we calculate the evolution of an 8.4 M _o˙ star from the main sequence until the oxygen ignition in the ONeMg core. We apply the latest electron-capture rate on ²⁰Ne, including the second forbidden transition, and investigate how the location of the oxygen ignition (center or off-center) and the Y _e distribution depend on the input physics and the treatment of the semiconvection and convection. The central density when the oxygen deflagration is initiated, ρ _c,def, can be significantly higher than that of the oxygen ignition thanks to the convection, and we estimate . We perform two-dimensional simulations of the flame propagation to examine how the final fate of the ONeMg core depends on the Y _e distribution and ρ _c,def. We find that the deflagration starting from leads to a collapse (thermonuclear explosion). Since our estimate of ρ _c,def exceeds this critical value, the ONeMg core is likely to collapse, although further studies of the convection and semiconvection before the deflagration are important.