Protoneutron Star Convection Simulated with a New General Relativistic Boltzmann Neutrino Radiation Hydrodynamics Code

Abstract

We investigate protoneutron star (PNS) convection using our newly developed general relativistic Boltzmann neutrino radiation hydrodynamics code. This is a pilot study for more comprehensive investigations later. As such, we take a snapshot of a PNS at 2.3 s after bounce from a 1D PNS cooling calculation and run our simulation for ∼160 ms in 2D under axisymmetry. The original PNS cooling calculation neglected convection entirely and the initial conditions were linearly unstable to convection. We find in our 2D simulation that convection is instigated there indeed and expands inward after being full-fledged. The convection then settled to a quasi-steady state after ∼100 ms, being sustained by the negative Y _e gradient, which is in turn maintained by neutrino emissions. It enhances the luminosities and mean energies of all species of neutrinos compared to 1D. Taking advantage of the Boltzmann solver, we analyse the possible occurrence of neutrino fast flavor conversion (FFC). We found that FFC is likely to occur in regions where Y _e is lower, and that the growth rate can be as high as ∼10 ^−1 cm ^−1 .

Keywords

• Neutron stars
• Core-collapse supernovae
• Supernova neutrinos
• Radiative transfer simulations
• Neutrino oscillations