Electron-capture Supernovae of Super-AGB Stars: Sensitivity on Input Physics

Stars of M ∼ 8-10 M _o- on their main sequence form strongly electron-degenerate oxygen-neon-magnesium (ONeMg) cores and become super-asymptotic giant branch stars. If such an ONeMg core grows to 1.38 M _o-, electron captures on ²⁰Ne(e, ν _e)²⁰F(e, ν _e)²⁰O take place and ignite O-Ne deflagration around the center. In this work, we perform two-dimensional hydrodynamical simulations of the propagation of the O-Ne flame to see whether such a flame triggers a thermonuclear explosion or induces a collapse of the ONeMg core due to subsequent electron capture behind the flame. We present a series of models to explore how the outcome depends on model parameters for a central density ranging between 10^9.80 and 10^10.20 g cm^-3, flame structures of both centered and off-centered ignition kernels, special and general relativistic effects, turbulent flame speed formulae, and the treatments of laminar burning phase. We obtain bifurcation between the electron-capture induced collapse and thermonuclear explosion depending mainly on the central density. We find that the ONeMg core obtained from stellar evolutionary models has a high tendency to collapse into a neutron star. We discuss the implications of the electron-capture supernovae in chemical evolution and the possible observational signals of this class of supernovae.