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  On the origin of highest energy gamma-rays from Mkn 501

Aharonian, F. A., Timokhin, A. N., & Plyasheshnikov, A. V. (2002). On the origin of highest energy gamma-rays from Mkn 501. Astronomy & Astrophysics, 384(3), 834-847.

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 Creators:
Aharonian, F. A.1, Author           
Timokhin, A. N.1, Author           
Plyasheshnikov, A. V.2, Author
Affiliations:
1Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society, ou_904550              
2Sternberg Astron Inst, Moscow 119899, Russia; Altai State Univ, Barnaul 656099, Russia, ou_persistent22              

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Free keywords: galaxies : BL Lacertae objects : individual : Mkn 501; cosmology : diffuse radiation; gamma rays : observations; gamma rays : theory
 Abstract: The spectra of very high energy gamma-radiation from distant extragalactic objects suffer significant deformations during the passage of primary gamma-rays through the intergalactic medium. The recently reported fluxes of diffuse infrared background radiation indicate that we detect, most probably, heavily absorbed TeV radiation from Mkn 421 and Mkn 501. This implies that the absorption-corrected spectrum of Mkn 501 may contain a sharp pile-up which contradicts to the predictions of the conventional models of TeV blazars, and thus may lead to the so-called "IR background-TeV gamma-ray crisis". To overcome this difficulty, in this paper we propose two independent hypotheses assuming that (i) the TeV radiation from Mkn 501 has a secondary origin, i.e. it is formed during the development of electron-photon cascades in the intergalactic medium initiated by primary gamma-rays; (ii) the pile-up in the source spectrum is a result of comptonization (in deep Klein-Nishina regime) of ambient optical radiation by an ultrarelativistic conical cold outflow (jet) with bulk motion Lorentz factor Gamma(0) less than or equal to 3 x 10(7). Within the uncertainties caused by the limited energy resolution of spectral measurements, the observed TeV radiation of Mkn 501 formally can be explained by the intergalactic cascade gamma-rays, assuming however an extremely low intergalactic magnetic field in the direction to the source at the level of less than or equal to10(18) G. We also demonstrate that the "bulk motion comptonization" scenario can quite naturally reproduce the unusual spectral features in the absorption-corrected TeV spectrum of Mkn 501, and briefly discuss the astrophysical implications of this hypothesis.

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Language(s): eng - English
 Dates: 2002-03
 Publication Status: Issued
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 27815
ISI: 000174448600012
 Degree: -

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Title: Astronomy & Astrophysics
  Alternative Title : Astron. Astrophys.
Source Genre: Journal
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Publ. Info: -
Pages: - Volume / Issue: 384 (3) Sequence Number: - Start / End Page: 834 - 847 Identifier: ISSN: 1432-0746