From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3

Recent LHAASO observations reveal ultrahigh-energy (UHE) gamma-ray emission from Cygnus~X-3 with evidence for orbital modulation, providing a rare opportunity to study particle acceleration and transport on binary scales. We develop a common binary–jet model that jointly explains the contemporaneous GeV–PeV spectra and orbital light curves. The GeV emission is produced by anisotropic inverse-Compton scattering of stellar photons by relativistic electrons, while multi-PeV protons escaping from the inner region produce TeV–PeV gamma rays through photohadronic and hadronuclear interactions. The GeV orbital modulation constrains the binary–jet geometry, allowing the UHE observations to probe the escaping proton population and its interaction with the circum-binary environment. We find that the UHE emission is strongly regulated by the accretion-driven wind structure. In the present state, a fast disk wind displaces much of the denser Wolf–Rayet (WR) wind from the escaping-proton trajectories, suppressing hadronuclear emission. Changes in the strength, collimation, or orientation of the disk wind can expose the escaping protons to a much denser WR wind and enhance the PeV gamma-ray luminosity by orders of magnitude. This provides a possible connection to the much brighter, though unconfirmed, PeV activity reported in the 1980s, and links UHE gamma-ray activity to the accretion and outflow state of the binary.