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On the Broad Band Energy Distribution of Blazars

Published online by Cambridge University Press:  19 July 2016

Laura Maraschi ,
Gabriele Ghisellini  and
Annalisa Celotti
Laura Maraschi
Affiliation:
Dipartimento di Fisica, Università di Milano, via Celoria 16, 20133 Milano, Italy
Gabriele Ghisellini
Affiliation:
Osservatorio di Torino, Strada Osservatorio 20, 10025 Torino, Italy
Annalisa Celotti
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 0KA, United Kingdom

Abstract

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The broad band energy distributions of blazars are revisited with particular emphasis on the sources detected in γ-rays by the Compton Observatory (GRO). The observed distributions can be broken down into two main components, corresponding to two broad peaks in the vFv representation. The first occurs in the FIR-optical range, the second in the MeV-GeV region. In the case of MKN 421, which may be representative of X-ray selected BL Lacs, the first peak is shifted to higher frequency (≃ 1016 Hz) and the γ-ray spectrum extends to TeV energies. There is general agreement that the first spectral component is due to synchrotron radiation from a relativistic jet, although some problems remain in deriving the spectrum and location of the emitting relativistic electrons. The second component, which in most objects extends from the X-ray to the γ-ray range, can be naturally interpreted as inverse Compton scattering by the same electrons producing the synchrotron photons, either on the synchrotron photons themselves (SSC) or on photons external to the jet. It is argued that multifrequency studies of these sources including γ-rays will allow to test Inverse Compton models and to distinguish between different sources of photons.

Keywords

Active Galactic Nuclei: blazarsRadiation Mechanisms: Synchrotron, Inverse ComptonUVX-raysγ-rays
Type
Correlations between Emission Components
Information
Symposium - International Astronomical Union , Volume 159: Multi-Wavelength Continuum Emission of AGN , 1994 , pp. 221 - 232
Copyright
Copyright © Kluwer 1994 

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