High-Energy Neutrino Emission from White Dwarf Mergers

TL;DR

White dwarf mergers may produce high-energy neutrinos through magnetic reconnection and cosmic-ray acceleration, serving as hidden sources that could significantly contribute to IceCube's observed neutrino flux, despite gamma-ray absorption.

Contribution

This paper proposes a novel mechanism linking white dwarf mergers to high-energy neutrino production and explores their potential as significant, yet hidden, cosmic-ray accelerators.

Findings

Neutrino signals can probe outflow dynamics and magnetic dissipation.

High-energy gamma-rays are absorbed, making these sources 'hidden' cosmic-ray accelerators.

Diffuse neutrino flux could account for a substantial part of IceCube observations.

Abstract

The merger of two white dwarfs is expected to result in a central fast rotating core surrounded by a debris disk, in which magnetorotational instabilities give rise to a hot magnetized corona and a magnetized outflow. The dissipation of magnetic energy via reconnection could lead to the acceleration of cosmic-rays in the expanding material, which would result in high energy neutrinos. We discuss the possibility of using these neutrino signals as probes of the outflow dynamics, magnetic energy dissipation rate and cosmic-ray acceleration efficiency. Importantly, the accompanying high-energy gamma-rays are absorbed within these sources because of the large optical depth, so these neutrino sources can be regarded as hidden cosmic-ray accelerators that are consistent with the non-detection of gamma-rays with Fermi-LAT. While the cosmic-ray generation rate is highly uncertain, if it reaches $\sim10^{45}\,\rm erg\,Mpc^{-3}\,yr^{-1}$, the diffuse neutrino flux could contribute a substantial fraction of the IceCube observations. We also evaluate the prospect of observing individual merger events, which provides a means for testing such sources in the future.