A comprehensive study of high-energy gamma-ray and radio emission from Cyg X-3
Résumé
We study high-energy γ-rays observed from Cyg X-3 by the Fermi Large Area Telescope and the 15-GHz emission observed by the Ryle Telescope and the Arcminute Microkelvin Imager. We measure the γ-ray spectrum averaged over strong flares much more accurately than before and find it well modelled by Compton scattering of stellar radiation by relativistic electrons with the power-law index of ≃3.5 and a low-energy cutoff at the Lorentz factor of ∼10^3. We find a weaker spectrum in the soft spectral state but only upper limits in the hard and intermediate states. We measure strong orbital modulation during the flaring state, well modelled by anisotropic Compton scattering of blackbody photons from the donor by jet relativistic electrons. We discover a weaker orbital modulation of the 15-GHz radio emission, which is well modelled by free–free absorption by the stellar wind. We then study cross-correlations between radio, γ-ray, and X-ray emissions. We find the cross-correlation between the radio and γ-ray emission peaks at a lag less than 1 d, while we detect a distinct radio lag of ∼50 d with respect to the soft X-rays in the soft spectral state.
Mots clés
acceleration of particles
gamma-rays: general
gamma-rays: stars
stars: jets
stars: individual: Cyg X-3
X-rays: binaries
electron: relativistic
jet: relativistic
X-ray: emission
modulation
radio wave
precession
Compton scattering
star
intermediate state
GLAST
power spectrum
absorption
anisotropy
gamma ray: energy
gamma ray: energy spectrum
energy: high
spectral
orbit
Lorentz
Domaines
Astrophysique [astro-ph]Origine | Fichiers éditeurs autorisés sur une archive ouverte |
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