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Comptonization of diffuse ambient radiation by a relativistic jet: The source of gamma rays from blazars?Recent Energy Gamma Ray Experiment Telescope (EGRET) observations of blazars have revealed strong, variable gamma-ray fluxes with no signatures of gamma-ray absorption by pair production. This radiation probably originates from the inner parts of relativistic jets which are aimed nearly toward us. On sub-parsec scales, the jet will be pervaded by radiation from the broad-line region, as well as by photons from the central continuum source (some of which will be scattered by thermal plasma). In a frame moving with the relativistic outflow, the energy of this ambient radiation would be enhanced. This radiation would be Comptonized by both cold and relativistic electrons in the jet, yielding (in the observer's frame) a collimated beam of X-rays and gamma rays. On the assumption that this process dominates self-Comptonization of synchrotron radiation, we develop a self-consistent model for variable gamma-ray emission, involving a single population of relativistic electrons accelerated by a disturbance in the jet. The spectral break between the X-ray and gamma-ray band, observed in 3C 279 and deduced for other blazars, results from inefficient radiative cooling of lower energy electrons. The existence of such a break strongly favors a model involving Comptonization of an external radiation field over a synchrotron self-Compton model. We derive constraints on such model parameters as the location and speed of the source, its dimensions and internal physical parameters, the maximum photon energies produced in the source, and the density and distribution of ambient radiation. Finally, we discuss how observations might discriminate between our model and alternative ones invoking Comptonization of ambient radiation.
Document ID
19950035673
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sikora, Marek
(University of Colorado, Boulder, CO United States)
Begelman, Mitchell C.
(University of Colorado, Boulder, CO United States)
Rees, Martin J.
(Institute of Astronomy Cambridge, United Kingdom)
Date Acquired
August 16, 2013
Publication Date
January 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 421
Issue: 1
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A67272
Funding Number(s)
CONTRACT_GRANT: NSF AST-91-20599
CONTRACT_GRANT: NAG5-2026
CONTRACT_GRANT: NSF INT-90-17207
CONTRACT_GRANT: NSF AST-88-16140
Distribution Limits
Public
Copyright
Other

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