PeV photon and neutrino flares from galactic gamma-ray binaries

TL;DR

This paper proposes that gamma-ray binaries can accelerate protons to PeV energies, producing hard spectra of sub-PeV photons and neutrinos, potentially explaining recent high-energy neutrino observations.

Contribution

It introduces a Monte Carlo model showing efficient PeV proton acceleration in gamma-ray binaries and links this to observed sub-PeV gamma-ray and neutrino events.

Findings

Protons can be accelerated to PeV energies in gamma-ray binary systems.

The model predicts hard spectra of sub-PeV photons and neutrinos.

Gamma-ray binaries may significantly contribute to the Galactic high-energy neutrino flux.

Abstract

The high-energy radiation from short period binaries containing a massive star with a compact relativistic companion was detected from radio to TeV gamma rays. We show here that PeV regime protons can be efficiently accelerated in the regions of collision of relativistic outflows of a compact object with stellar winds in these systems. The accelerated proton spectra in the presented Monte Carlo model have an upturn in the PeV regime and can provide very hard spectra of sub-PeV photons and neutrinos by photo-meson processes in the stellar radiation field. Recent report of a possible sub-PeV gamma-ray flare in coincidence with a high-energy neutrino can be understood in the frame of this model. The gamma-ray binaries may contribute substantially to the Galactic component of the detected high-energy neutrino flux.