Long-Term Studies of Cyg X-3 High-Mass X-ray Binary

Abstract

Cyg X-3 is the famous binary system containing a black hole that is actively studied through a wide range of the electromagnetic spectrum, from radio wavelengths to ultra-high-energy gamma-rays, but still not well-understood. The Cyg X-3 focusing investigations obtained from the long-term observations at 800 GeV–100 TeV energies with the SHALON telescope are presented. The modulation of the γ-ray emission detected in these studies with an orbital period of 4.8 h was found, proving the identity of the observed object with Cyg X-3. The comparison of light curves in the wide energy range from radio to very high energy γ-rays, folded on the Cyg X-3 orbital period, revealed the differences in the modulation amplitude and phase shifts. The studies of Cyg X-3 activity at very-high energies, including information about TeV and MeV-GeV flare and quenched states and the relationship between the ones in the entire wide energy range, are presented. The modulation of TeV γ-ray flux with orbit along with the high luminosity of the companion star of Cyg X-3 and the close orbit of binary leads to an efficient generation of the part of γ-ray emission in the inverse Compton scattering. The correlation of TeV fluxes with the flaring activity of Cyg X-3 at X-ray and radio ranges could be related to processes of powerful mass ejections from the central regions around the black hole.