PeV Photon and Neutrino Flares from Galactic Gamma-Ray Binaries

The high-energy radiation from short period binaries containing a massive star with a compact relativistic companion was detected from radio to TeV γ-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 photomeson processes in the stellar radiation field. The recent report of a possible sub-PeV γ-ray flare in coincidence with a high-energy neutrino can be understood in the frame of this model. The γ-ray binaries may contribute substantially to the Galactic component of the detected high-energy neutrino flux.