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

Abstract

Stars of M ~ 8–10 M⊙ 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⊙, 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.

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