Query : 2011A&A...529A.120C

2011A&A...529A.120C - Astronomy and Astrophysics, volume 529A, 120-120 (2011/5-1)

Absorption of high-energy gamma rays in Cygnus X-3.


Abstract (from CDS):

The microquasar Cygnus X-3 was detected at high energies by the gamma-ray space telescopes AGILE and Fermi. The gamma-ray emission is transient, modulated with the orbital period and seems related to major radio flares, i.e. to the relativistic jet. The GeV gamma-ray flux can be substantially attenuated by internal absorption with the ambient X-rays. We examine quantitatively the effect of pair production in Cygnus X-3 and put constraints on the location of the gamma-ray source. Cygnus X-3 exhibits complex temporal and spectral patterns in X-rays. During gamma-ray flares, the X-ray emission can be approximated by a bright disk black-body component and a non-thermal tail extending in hard X-rays, which is possibly related to a corona above the disk. We calculate numerically the exact optical depth for gamma rays above a standard accretion disk. Emission and absorption in the corona are also investigated. GeV gamma rays are significantly absorbed by soft X-rays emitted from the inner parts of the accretion disk. The absorption pattern is complex and anisotropic. Isotropization of X-rays caused by Thomson scattering in the companion-star wind tends to increase the gamma-ray opacity. Gamma rays from the corona suffer from strong absorption by photons from the disk and cannot explain the observed high-energy emission, unless the corona is unrealistically extended. The lack of an absorption feature in the GeV emission indicates that high-energy gamma rays should be located at a minimum distance ∼108-1010cm from the compact object. The gamma-ray emission is unlikely to have a coronal origin.

Abstract Copyright:

Journal keyword(s): radiation mechanisms: non-thermal - stars: individual: Cygnus X-3 - gamma rays: general - X-rays: binaries - accretion, accretion disks

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4330 0
2 V* V1521 Cyg HXB 20 32 25.78 +40 57 27.9           WN4/5-6/7 1936 2

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