Supernova neutrino signals based on long-term axisymmetric simulations

TL;DR

This paper analyzes neutrino signals from core-collapse supernovae using axisymmetric simulations, revealing late-phase temporal fluctuations driven by fallback accretion and proposing methods to estimate total neutrino energy from detector data.

Contribution

It introduces detailed modeling of late-phase neutrino signals, highlighting fallback accretion effects and providing updated formulas for estimating total neutrino energy from observations.

Findings

Late-phase neutrino emissions are variable, not steady.

Fallback accretion influences late-time neutrino fluctuations.

IceCube is most effective for detecting temporal variations.

Abstract

We study theoretical neutrino signals from core-collapse supernova (CCSN) computed using axisymmetric CCSN simulations that cover the post-bounce phase up to $\sim 4$~s. We provide basic quantities of the neutrino signals such as event rates, energy spectra, and cumulative number of events at some terrestrial neutrino detectors, and then discuss some new features in the late phase that emerge in our models. Contrary to popular belief, neutrino emissions in the late phase are not always steady, but rather have temporal fluctuations, the vigor of which hinges on the CCSN model and neutrino flavor. We find that such temporal variations are not primarily driven by proto-neutron star (PNS) convection, but by fallback accretion in exploding models. We assess the detectability of these temporal variations, and find that IceCube is the most promising detector with which to resolve them. We also update fitting formulae first proposed in our previous paper for which the total neutrino energy (TONE) emitted at the CCSN source is estimated from the cumulative number of events in each detector. This will be a powerful technique with which to analyze real observations, particularly for low-statistics data.