Hydrodynamic Simulations of Electron-capture Supernovae: Progenitor and Dimension Dependence

Abstract

We present neutrino-transport hydrodynamic simulations of electron-capture supernovae (ECSNe) in \texttt{FLASH} with new two-dimensional (2D) collapsing progenitor models. These progenitor models feature the 2D modelling of oxygen-flame propagation until the onset of core collapse. We perform axisymmetric simulations with 6 progenitor models that, at the time of collapse, span a range of propagating flame front radii. For comparison, we also perform a simulation with the same setup using the canonical, spherically-symmetrical progenitor model n8.8. We found that the variations in the progenitor models inherited from simulations of stellar evolution and flame propagation do not significantly alter the global properties of the neutrino-driven ECSN explosion, such as the explosion energy ($\sim1.36$-$1.48\times10^{50}$ erg) and the mass ($\sim0.017$-$0.018M_\odot$) and composition of the ejecta. Due to aspherical perturbations induced by the 2D flame, the ejecta contains a small amount ($\lesssim1.8\times10^{-3}~M_\odot$) of low-$Y_e$ ($0.35<Y_e<0.4$) component. The baryonic mass of the protoneutron star is $\sim1.34~M_\odot$ ($\sim1.357~M_\odot$) with the new (n8.8) progenitor models when simulations end at $\sim400$ ms and the discrepancy is due to updated weak-interaction rates in the progenitor evolutionary simulations. Our results reflect the nature of ECSN progenitors containing a strongly degenerate ONeMg core and suggest a standardized ECSN explosion initialized by ONeMg core collapse. Moreover, we carry out a rudimentary three-dimensional simulation and find that the explosion properties are fairly compatible with the 2D counterpart. Our paper facilitates a more thorough understanding of ECSN explosions following the ONeMg core collapse, though more three-dimensional simulations are still needed.