Astrophysics and Space Science

, Volume 246, Issue 2, pp 299–307 | Cite as

Variable radio echoes from a jet in QSO 0957+561

  • V. L. Oknyanskij


Time delay determinations in astrophysics are used most often to find time delays between flux density variations of different spectral bands and/or spectral lines in AGNs and different images of gravitationally lensed QSOs. Here we consider a new algorithm for a complex case, when the time delay is itself a linear function of time and the intensity of echo response is power function of the delay. We apply this method to investigate optical-to-radio delay in the double quasar 0957+561, which is a generally accepted case of gravitational lensing.

Radio-optical correlation in QSO 0957+561 was first reported by Oknyanskij and Beskin (1993, hereafter OB) on the basis of radio observations made in the years 1979 to 1990. OB used an idea to take into account the known gravitational lensing time delay to get combined radio and optical light curves and then to use them for determination of the possible radio-from-optical time delay. It was found this way that radio variations (5 MHz) followed optical ones by about 6.4 years with high level of correlation (≈0.87). Using new radio data (Haarsmaet al., 1996), for the interval 1979–1994 we find nearly the same value for the optical-to-radio delay as has been found before. Additionally we suspect that the time delay value is linearly increasing at about 110 days per year while the portion of reradiated flux in the radioresponse is decreasing.

Obtained results indicate that the optical and radio emitting regions are physically related, but have distinct size scales, locations and possibly radiation mechanisms. We conclude that the results can be explained by simple model were the variable radio source is ejected from the central part of the QSO compact component and that the changing time delay between the optical and radio light curves is consequence of light travel effect.


Time Delay Radio Source Light Curf Flux Density Variation Radio Observation 
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  1. Beskin, G.M. and Oknyanskij, V.L.: 1992, ‘Gravitational Lens’, in:Lecture Notes in Physics 406, Springer Verlag, 67.Google Scholar
  2. Beskin, G.M. and Oknyanskij, V.L.: 1995,Astron. Astrophys. 304, 341.Google Scholar
  3. Clements, S.D., Smith, A.G. and Aller, H.D.: 1995,Astron. J. 110, 529.Google Scholar
  4. Falko, E.E., Wambsganss, J. and Schneider, P.: 1991,Mon. Not. R. Astron. Soc. 251, 698.Google Scholar
  5. Gaskell, C.M. and Spark, L.S.: 1986,Astrophys. J. 305, 175.Google Scholar
  6. Haarsma, D.B., Hewitt, J.N., Burke, B.F. and Lehar, J.: 1995, in: C.S. Kochanek and J.N. Hewitt (eds.),Astrophysical Application of Gravitational Lensing: IAU Symp. 173 in Melbourne, Kluwer, Dordrecht, 43.Google Scholar
  7. Haarsma, D.B., Hewitt, J.N., Lehar, J. and Burke, B.F.: 1996,Astrophys. J., in press.Google Scholar
  8. Hufnagel, B.R. and Bregman, J.N.: 1992,Astrophys. J. 386, 473.Google Scholar
  9. Kundić, T., Colley, W.N., Gott, R.J., Malhotra, S., Ue-Li, P., Phoads, J.E., Stanek, K.Z., Turner, E.L. and Wambsganss, J.: 1995,Astrophys. J. 455, L5.Google Scholar
  10. Oknyanskij, V.L. and Beskin, G.M.: 1993, in: J. Surdejet al. (eds.),Gravitational Lenses in the Universe: Proceedings of the 31st Liege International Astrophysical Colloquium, Université de Liège, Institute d'Astrophysique, Liège, Belgium, 65.Google Scholar
  11. Oknyanskij, V.L.: 1994,Astrophys. Space Sci. 222, 157.Google Scholar
  12. Oknyanskij, V.L.: 1995, in: C.S. Kochanek and J.N. Hewitt (eds.),Astrophysical Application of Gravitational Lensing: IAU Symp. 173 in Melbourne, Kluwer, Dordrecht, 45.Google Scholar
  13. Oscoz, A., Serra-Ricart, M., Goicochea, L.J., Buitrago, J. and Mediavilla, E.: 1996,Astrophys. J. 470, L19.Google Scholar
  14. Pelt, J., Kayser, R., Refsdal, S. and Schramm, T.: 1996,Astron. Astrophys. 286, 775.Google Scholar
  15. Press, W.H., Rybicki, G.B. and Hewitt, J.N.: 1992,Astrophys. J. 385, 404.Google Scholar
  16. Refsdal, S.: 1964,Mon. Not. R. Astron. Soc. 128, 307.Google Scholar
  17. Scargle, J.D.: 1989,Astrophys. J. 343, 887.Google Scholar
  18. Schild, R.E.: 1990,Astron. J. 100, 1771.Google Scholar
  19. Schild, R.E. and Thomson, D.J.: 1996, in: C.S. Kochanek and J.N. Hewitt (eds.),Astrophysical Application of Gravitational Lensing: IAU Symp. 173 in Melbourne, Kluwer, Dordrecht, 51.Google Scholar
  20. Tornikoski, M., Valtaoja, E., Terãsrantra, H., Smith, A.J., Nair, A.D., Clements, S.D. and Leacock, R.J.: 1994,Astron. Astrophys. 289, 673.Google Scholar
  21. Usher, P.D.: 1972,Astrophys. J. 172, L25.Google Scholar
  22. Vanderriest, C., Schneider, J., Herpe, G., Chevreton, M., Moles, M. and Wlérick, G.: 1989,Astron. Astrophys. 215, 1.Google Scholar

Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • V. L. Oknyanskij
    • 1
  1. 1.Sternberg State Astronomical InstituteMoscow State UniversityRussia

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