Neutrinos from beta processes in a presupernova: probing the isotopic evolution of a massive star

TL;DR

This paper models neutrino emissions from a presupernova star, highlighting the significant role of beta processes in the neutrino flux, which can enhance detection prospects for nearby supernova precursors.

Contribution

It provides a detailed calculation of neutrino fluxes including beta processes using a comprehensive isotope network, improving understanding of presupernova neutrino signals.

Findings

Beta processes dominate the neutrino flux in the last hours before collapse.

High-energy tail of neutrinos mainly from decay and electron capture on isotopes.

Detection of presupernova neutrinos is feasible with current detectors at 1 kpc.

Abstract

We present a new calculation of the neutrino flux received at Earth from a massive star in the $\sim 24$ hours of evolution prior to its explosion as a supernova (presupernova). Using the stellar evolution code MESA, the neutrino emissivity in each flavor is calculated at many radial zones and time steps. In addition to thermal processes, neutrino production via beta processes is modeled in detail, using a network of 204 isotopes. We find that the total produced $\nu_{e}$ flux has a high energy spectrum tail, at $E \gtrsim 3 - 4$ MeV, which is mostly due to decay and electron capture on isotopes with $A = 50 - 60$. In a tentative window of observability of $E \gtrsim 0.5$ MeV and $t < 2$ hours pre-collapse, the contribution of beta processes to the $\nu_{e}$ flux is at the level of $\sim90\%$ . For a star at $D=1$ kpc distance, a 17 kt liquid scintillator detector would typically observe several tens of events from a presupernova, of which up to $\sim 30\%$ due to beta processes. These processes dominate the signal at a liquid argon detector, thus greatly enhancing its sensitivity to a presupernova.