Measuring the neutron star compactness and binding energy with supernova neutrinos

TL;DR

This study demonstrates that supernova neutrino signals detected by water Cherenkov detectors can measure neutron star binding energy with about 11% accuracy without priors, improving to 3% with assumptions, impacting neutron star property assessments.

Contribution

It provides a method to measure neutron star binding energy precisely using neutrino signals without relying on prior spectral assumptions.

Findings

11% precision on binding energy without priors

3% precision achievable with priors like energy equipartition

Neutral current events on oxygen do not improve precision

Abstract

We investigate the precision with which a neutron star gravitational binding energy can be measured through the supernova neutrino signal, without assuming any prior such as the energy equipartition hypothesis, mean energies hierarchy or constraints on the pinching parameters that characterize the neutrino spectra. We consider water Cherenkov detectors and prove that combining inverse beta decay with elastic scattering on electrons is sufficient to reach $11\%$ precision on the neutron star gravitational binding energy already with Super-Kamiokande. The inclusion of neutral current events on oxygen in the analysis does not improve the precision further. We show that $3\%$ precision can be achieved if priors are introduced, such as energy equipartition. We discuss the implications of our findings on the properties of the newly formed neutron star, in particular concerning the assessment of the compactness or mass--radius relation.