Journal Article

γ-rays from the IC e<sup>±</sup> pair cascade in the radiation field of an accretion disc: application to Cen A

J. Sitarek and W. Bednarek

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 401, issue 3, pages 1983-1988
Published in print January 2010 | ISSN: 0035-8711
Published online January 2010 | e-ISSN: 1365-2966 | DOI:
γ-rays from the IC e± pair cascade in the radiation field of an accretion disc: application to Cen A

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The very short time-scale variability of TeV γ-ray emission from active galaxies suggests that the acceleration process of particles and the production of primary γ-rays likely occur relatively close to the accretion disc. We calculate the γ-ray spectra produced in an inverse Compton e± pair cascade initiated by primary γ-rays which are injected close to the surface of the accretion disc. Possible synchrotron energy losses of secondary cascade e± pairs are also taken into account. Since the soft radiation field is anisotropic, the resulting γ-ray spectra strongly depend on the observation angle. We investigate their basic properties for different parameters describing such a model. The model is applied to the misaligned blazar Cen A recently detected in the TeV γ-rays. We conclude on the site of the γ-ray emission region in Cen A based on the comparison of the model with the observations of this source in the GeV–TeV energy range.

Keywords: radiation mechanisms: non-thermal; galaxies: active; galaxies: individual: Cen A; gamma-rays: theory

Journal Article.  4790 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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