GeV gamma-rays and TeV neutrinos from very massive compact binary systems: the case of WR 20a

Abstract

Abstract Massive Wolf—Rayet stars in a compact binary system are characterized by very strong winds which collide, creating a shock wave. If the wind nuclei, from helium up to oxygen, accelerated at the shock can reach large enough energies, they suffer disintegration in collisions with soft thermal radiation from the massive stars injecting relativistic protons and neutrons. Protons collide with the matter of the wind and a fraction of neutrons collide with the massive stars producing γ-rays and neutrinos via decay of pions. We calculate γ-ray fluxes from inverse Compton e± pair cascades initiated by primary γ-rays and leptons, which are produced by protons, and the neutrino fluxes, produced by protons and neutrons, for the example compact massive binary WR 20a. From normalization of these cascade γ-ray spectra to the fluxes of the EGRET sources 2EG J1021 − 5835 and 2EG J1049 − 5847 observed in the direction of WR 20a, we conclude that this massive binary can be detected by the IceCube type of neutrino detector. The estimated muon neutrino event rate inside the 1-km2 detector during 1 year is between a few and a few tens, depending on the spectrum of accelerated nuclei.