From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3
Abstract
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.
Related
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BibTeX
@misc{wan2026from,
title = {{From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3}},
author = {Su-Yu Wan and Ruo-Yu Liu and Xing-Fu Zhang and Dmitriy Khangulyan},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11881},
eprint = {2610.11881},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11881},
}
RIS
TY - UNPB
TI - From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3
AU - Su-Yu Wan
AU - Ruo-Yu Liu
AU - Xing-Fu Zhang
AU - Dmitriy Khangulyan
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11881
UR - https://arxiv.org/abs/2610.11881
AB - 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.
ER -