Investigating binary-neutron-star mergers as production sites of high-energy neutrinos

TL;DR

This paper explores how binary-neutron-star mergers could accelerate cosmic rays and produce high-energy neutrinos, analyzing their potential contribution to observed cosmic-ray and neutrino fluxes and constraining source parameters.

Contribution

It models neutrino production from BNS mergers considering photon field evolution and cosmic-ray interactions, providing new constraints on baryon acceleration in these events.

Findings

Predicted diffuse neutrino flux depends on photon field evolution.

Constraints on baryon acceleration fraction from CR and neutrino data.

Potential contribution of BNS mergers to sub-ankle cosmic rays.

Abstract

The end state of binary-neutron-star (BNS) mergers can manifest conditions to produce high-energy neutrinos. Inspired by the event GW170817, detected in gravitational waves and in optical/infrared emission, we investigate a scenario in which cosmic-ray (CR) particles are accelerated, in a population of BNS mergers, in the energy range that might contribute from the \textit{knee} to the \textit{ankle} of the CR measured spectrum. By taking into account the measured thermal and non-thermal energy density of the photon fields in the source environment as a function of the time after the merger, we model the CR interactions and the consequent neutrino production. We propagate the escaped CR and neutrino fluxes through the extragalactic space and compare the expected diffuse fluxes to the experimental data and current limits. Depending on the CR spectral and composition parameters at acceleration, and on the possible contribution to the \textit{sub-ankle} CR flux, we discuss the predicted diffuse neutrino flux associated to this class of astrophysical objects, as a function of the details of the photon field characterizing the merger stage, including its evolution in time. We constrain the fraction of accelerated baryons in the source site given the BNS merger rate per volume, taking into account at the same time the constraints from the measured CR and neutrino fluxes.