Multi-Frequency Studies Of Intrinsic Intraday Variability

  • Stefan J. Wagner


Intraday variability is detected in Blazars throughout the electromagnetic spectrum. Onlyradio emission is affected by interstellar scintillation. The characteristics of variability observedat different frequencies are often similar and suggest that intrinsic variations also contribute tothe changes detected in the radio wavelength regime. This in turn implies very high brightnesstemperatures.Unambiguous signatures of scintillation and of intrinsic changes have been identified. The propertiesof intrinsic variations are reviewed to illustrate their potential contribution to variability in theradio domain. Such intrinsic changes need to be discriminated against when studying scintillationin quasars and BL Lac objects. Observations of scintillating sources and of sources with significantintrinsic IDV suggest interesting modifications to the standard paradigm of AGN.


Brightness Temperature Photon Density Synchrotron Emission Intrinsic Variation VLBI Observation 
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  1. Begelman, M., Rees, M. and Sikora, M.: 1994, Astrophys. J. Lett. 429, 57–60.ADSCrossRefGoogle Scholar
  2. de Bruyn, A.G.: 1988, Proceedings of IAU Symp. 129, 97–98.Google Scholar
  3. Dennet-Thorpe, J. and de Bruyn, A.G.: 2000, Astrophys. J. Lett. 529, 65–68.ADSCrossRefGoogle Scholar
  4. Hartman, R.c., Collmar, W., von Montigny, C. and Dermer, C.D.: 1997, Proceedings Fourth Compton Symposium. AIP 410 (1), 307–328.ADSGoogle Scholar
  5. Harvey G.A., et al.: 1972, Astrophys. Lett. 11, 147–492.ADSGoogle Scholar
  6. Heidt, J. and Wagner, S.J.: 1996, Astron. Astrophys. 305, 42–52.ADSGoogle Scholar
  7. Heidt, J. and Wagner, S.J.: 1998, Astron. Astrophys. 329. 853–862.ADSGoogle Scholar
  8. Heeschen. D., Krichbaum, T., Schalinski, C. and Witzel, A.: 1987, Astron. J. 94, 1493–5072.ADSCrossRefGoogle Scholar
  9. Junor, W., Biretta, J.A. and Livio, M.: 1999, Nature 401, 891–892.ADSCrossRefGoogle Scholar
  10. Kedziora-Chudczer, L., Jauncey, D.L., et al.: 1997, Astrophys. J. Lett. 490, 9–12.ADSCrossRefGoogle Scholar
  11. Mannheim, K.: 1998, Science 279, 684–686.ADSCrossRefGoogle Scholar
  12. Marscher, A., Marchenko-Jorstad, S., Mattox, J., Wehrle, A. and Aller, M.: 2000, Proceedings: Astrophysical Phenomena Revealed by Space VLBI, ISAS, 39–46.Google Scholar
  13. Maxscher, A.P.: 1992, Proceedings: Physics of Active Galactic Nuclei, Springer, p. 510.Google Scholar
  14. Mattox, J.R., Wagner, S.J., Malkan, M., et al.: 1997, Astrophys. J. 476, 692–712.ADSCrossRefGoogle Scholar
  15. Oke, J.B.: 1967, Astrophys. J. 147, 901–907.ADSCrossRefGoogle Scholar
  16. Peng, B., Krans, A., Krichbaum, T.P., Müller, S., et al.: 2000, Astron. Astrophys. 353, 937–943.ADSGoogle Scholar
  17. Qian, S.-J., Quirrenbach, A., Witzel, A., et al.: 1991, Astron. Astrophys. 241, 15–21.ADSGoogle Scholar
  18. Quirrenbach, A., Witzel, A., Wagner, S.J., et al.: 1991, Astrophys. J. 372, L71–L74.ADSCrossRefGoogle Scholar
  19. Readhead, A.: 1994, Astrophys. J. 426, 51–59.ADSCrossRefGoogle Scholar
  20. Spada, M., Salvati, M. and Pacini, E: 1999, Astrophys. J. 511, 136–141.ADSCrossRefGoogle Scholar
  21. Wagner, S.J.: 1992, Proceedings: Gravitational Lenses, Springer, 189–195.Google Scholar
  22. Wagner, S.J. and Witzel, A.: 1995, Annu. Rev. Astron. Astrophys. 33, 163–197.ADSCrossRefGoogle Scholar
  23. Wagner, S.J., Witzel, A., Krichbaum, T.P., et al.: Astron. Astrophys. 271, 344–352.Google Scholar
  24. Wagner, S.J., Witzel, A., Heidt, J., et al.: Astron. J. 111, 2187–2212.Google Scholar
  25. Witzel, A., Heeschen, D., Schalinski, C., et al.: 1986, Mitt. Astron. Ges. 65, 239–241.ADSGoogle Scholar

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© Springer Science+Business Media Dordrecht 2001

Authors and Affiliations

  • Stefan J. Wagner
    • 1
  1. 1.LSW HeidelbergGermany

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