Bifurcated Impact of Neutrino Fast Flavor Conversion on Core-collapse Supernovae Informed by Multi-angle Neutrino Radiation Hydrodynamics

Abstract

In this {\it Letter}, we present a compelling and robust argument for the roles of neutrino fast flavor conversion (FFC) in the explosion mechanism of core-collapse supernova (CCSN), combining the {\it multi-angle} FFC subgrid model rooted in quantum kinetic theory with the multi-dimensional four-species Boltzmann neutrino radiation hydrodynamics. Employing various progenitor masses and the nuclear equations of states, we find that the effect of FFC on CCSN explosion is bifurcated depending on the progenitors. For the lowest-mass progenitor, FFC facilitates the shock revival and enhances the explosion energy, whereas for higher-mass progenitors its impact is inhibitory. We identify the mass accretion rate as the key determinant governing this bifurcation. When the mass accretion rate is low (high), the contribution of FFC to neutrino heating becomes positive (negative), because the heating efficiency enhancement via FFC-driven spectral hardening of electron-type neutrinos dominates over (is outweighed by) the concurrent reduction in neutrino luminosity. Our results further highlight the limitations of approximate neutrino transport, and demonstrate that a multi-angle treatment is essential for accurately capturing FFC effects; otherwise, FFCs are missed and even generated spuriously.

Figures (4)

• Figure 1: Time evolution of the averaged shock radii. The solid and dashed lines represent no-oscillation and FFC models, respectively. The inset shows the part of the shock evolution for the failed models (simple moving average (SMA) with time window $20\,\mathrm{ms}$ is taken for visibility).
• Figure 2: Meridian map of the entropy per baryon for the $9M_\odot$ VM EOS model at the $260\,\mathrm{ms}$ after bounce. Left and half panels correspond to no-oscillation and FFC models, respectively. The magenta line represent the gain radius. For the FFC model, outer contour of the FFC region is shown with the red line.
• Figure 3: Top: Meridian map of the FFC growth rate for the no-oscillation model at $260\,\mathrm{ms}$ for the multi-angle (right) and the one reconstructed with the Minerbo closure (left). The gain radius is shown with the magenta dashed line. The white lines represent the radii which correspond to the density of $10^{10}$, $10^{11}$, $10^{12}\,\mathrm{g}\,\mathrm{cm}^{-3}$. Middle: Electron-lepton number (ELN) at the $r=45\,\mathrm{km}$ on the equator. Multi-angle and Minerbo cases are compared. The negative ELN region, which is the main driver of FFC, are highlighted with red (multi-angle) and cyan (Minerbo), respectively. Bottom: same as the middle panel, but for the $r=70\,\mathrm{km}$ on the south pole ($\theta=\pi$).
• Figure 4: Time evolution of the neutrino heating rates $\dot Q$ (top), neutrino energy luminosities $L_\nu$ (middle), mean neutrino energies $\langle\epsilon_\nu\rangle$ (bottom) for the $9M_\odot$ VM EOS model (left column) and the $20M_\odot$ VM EOS model (right column). The solid and dashed lines denote the no-oscillation and FFC models, respectively.