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Viewing angles in some selected BL Lac objects

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Abstract

A selected subset of BL Lac objects were monitored with VLBI techniques at multifrequencies. Apparent superluminal motion and X-rays were detected in all of the monitored sources. From the observational data, kinematic parameters, geometric parameters and beaming effects for the ‘core’ of the selected BL Lac objects have been estimated. Our results indicate that some BL Lacs have large Lorentz factors and small viewing angles; relativistic beaming effects are strongly present in these sources. On the other hand, some BL Lacs have small Lorentz factors; their viewing angles are quite large. It does not seem possible to avoid the fact that some BL Lac objects are not oriented particularly close to the line of sight. It conflicts with the basic assumption of the accepted theories for explaining the characteristics of BL Lac objects at present. Also, it seems that the BL Lac objects in the class I of the Burdige and Hewitt's classification have larger viewing angles than those int he class II. The whole BL Lac classification could be a misnomer: the sources classified as ‘BL Lac objects’ are a mixture of physically different populations with different parent objects.

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References

  1. Antonucci, R.R.J. and Ulvestad, J.S.: 1985,Astron. Astrophys. 294, 158.

    Google Scholar 

  2. Bååth, L.B., Elgered, G., Lundqvist, G., Graham, D., Weiler, K.W., Seielstad, G.A., Tallqvist, S. and Schilizzi, R.T.: 1981,Astron. Astrophys. 96, 316.

    Google Scholar 

  3. Bååth, L.B. and Zhang, F.J.: 1991a,Astron. Astrophys. 243, 328.

    Google Scholar 

  4. Bååth, L.B. and Zhang, F.J.: 1991b,Astron. Astrophys. 250, 50.

    Google Scholar 

  5. Bååth, L.B. and Zhang, F.J.: 1992,Astron. Astrophys. 262, 1.

    Google Scholar 

  6. Bååth, L.B.: 1992, in: E. Valtaoja and M. Valtonen (eds.),Variability of Blazars, Cambridge University Press, Cambridge, p. 197.

    Google Scholar 

  7. Bååth, L.B.: 1992, in E. Valtaoja and M. Valtonen (eds.),Variability of Blazars, Cambridge University Press, Cambridge, p. 229.

    Google Scholar 

  8. Blandford, R.D. and Rees, M.J.: 1978, in: A. Wolfe (ed.),Pittsburgh Conference on BL Lac Objects, Univ. Pittsburg Press, p. 328.

  9. Blandford, R.D. and Königl, A.: 1979,Astrophys. J. 232, 34.

    Google Scholar 

  10. Brown, L.M.J., Robson, E.I., Gear, W.K., Hughes, D.H., Griffin, M. J., Geldzahler, B.J., Scgwartz, P.R., Smith, M.G., Smith, A.G., Shepherd, D.W., Webb, J.R., Valtaoja, E., Terasranta, H. and Salonen, E.: 1989,Astrophys. J. 240, 129.

    Google Scholar 

  11. Browne, I.W.A.: 1989, in: L. Maraschi, T. Maccacaro and M.-H. Ulrich (eds.),BL Lac Objects, Springer, Berlin, p. 401.

    Google Scholar 

  12. Burbidge, G. and Hewitt, A.: 1989, in: L. Maraschi, T. Maccacaro and M.-H. Ulrich (eds.),BL Lac Objects, Springer, Berlin, p. 412.

    Google Scholar 

  13. Burbidge, G. and Hewitt, A.: 1992, in: E. Valtaoja and M. Valtonen (eds.),Variability of Blazars, Cambridge University Press, Cambridge, p. 4.

    Google Scholar 

  14. Chu, H.S., Bååth, L.B., Rantakyro, F.T. and Zhang, F.J.: 1995,Astron. Astrophys., in press.

  15. Cohen, M.H. and Unwin, S.C.: 1984, in: R. Fanti, K. Kellerman and G. Setti (eds.),VLBI and Compact Radio Sources, Reidel, Dordrecht, p. 95.

    Google Scholar 

  16. Daly, R.A. and Marscher, A.P.: 1988,Astrophys. J. 334, 539.

    Google Scholar 

  17. Eckart, A., Witzel, A., Biermann, P., Johnston, K.J., Simon, R., Schalinski, C. and Kuhr, H.: 1987,Astron. Astrophys. 67, 121.

    Google Scholar 

  18. Gabuzda, D.C., Wardle, J.F.C. and Roberts, D.H.: 1989a,Astrophys. J. 336, L59.

    Google Scholar 

  19. Gabuzda, D.C., Wardle, J.F.C. and Roberts, D.H.: 1989b,Astrophys. J. 338, 743.

    Google Scholar 

  20. Ghisellini, G., Padovani, A., Celotti, A. and Maraschi, L.: 1993,Astrophys. J. 407, 65.

    Google Scholar 

  21. Giommi, P., Barr, P., Garilli, B., Maccagni, D. and Pollock, A.M.T.: 1990,Astrophys. J. 356, 432.

    Google Scholar 

  22. Hughes, P.A., Aller, H.D. and Aller, M.F.: 1989a,Astrophys. J. 341, 54.

    Google Scholar 

  23. Hughes, P.A., Aller, H.D. and Aller, M.F.: 1989b,Astrophys. J. 341, 68.

    Google Scholar 

  24. Landau, R., Jones, T.W., Epstein, E.E., Neugebauer, G., Soifer, B.T., Werner, M.W., Puschell, J.J. and Balonek, T.J.: 1983,Astrophys. J. 268, 68.

    Google Scholar 

  25. Ledden, J.E. and Aller, H.D.: 1976,Nature 260, 752.

    Google Scholar 

  26. Makino, F., Tanaka, Y., Matsuoka, M., Koyama, K., Inoue, H., Makishima, K., Hoshi, R. and Hayakawa, S.: 1987,Astrophys. J. 313, 662.

    Google Scholar 

  27. Marscher, A.P.: 1977,Astrophys. J. 216, 24.

    Google Scholar 

  28. Marscher, A.P.: 1987, in: J.A. Zensus and T.J. Pearson (eds.),Superluminal Radio Sources, Cambridge University Press, Cambridge, p. 280.

    Google Scholar 

  29. Marscher, A.P., Shaffer, D.B., Booth, R.S. and Geldzahler, R.J.: 1987,Astrophys. J. 319, L69.

    Google Scholar 

  30. Mufson, S.L., Huttler, D.J. and Kondo, Y.: 1989, in: L. Maraschi, T. Maccacaro and M.-H. Ulrich (eds.),Lecture Notes in Physics, 334: BL Lac Objects, Springer-Verlag, p. 341.

  31. Mutel, R.L., Phillips, R.B., Su, B.M. and Bucciferro, R.R.: 1990,Astrophys. J. 352, 81.

    Google Scholar 

  32. O'Dea, C.P., Barvainis, R. and Challis, P.M.: 1988,Astron. J. 96, 435.

    Google Scholar 

  33. Pearson, T.J. and Zensus, J.A.: 1987, in: J.A. Zensus and T.J. Pearson (eds.),Superluminal Radio Sources, Cambridge University Press, Cambridge, p. 1.

    Google Scholar 

  34. Padovani, P.: 1992,Monthly Notices Roy. Astron. Soc. 257, 404.

    Google Scholar 

  35. Robson, I.: 1992, in: E. Valtaoja and M. Valtonen (eds.),Variability of Blazars, Cambridge University Press, Cambridge, p. 111.

    Google Scholar 

  36. Shaffer, D.B.: 1978, in: A. Wolfe (ed.),Pittsburgh Conference on BL Lac Objects, Univ. Pittsburg Press, p. 68.

  37. Simon, R.S., Hall, J., Johnston, K.J., Spencer, J.H., Waak, J.A. and Mutel, R.L.: 1988,Astrophys. J. 326, L5.

    Google Scholar 

  38. Teräsranta, H. and Valtaoja, E.: 1994,Astron. Astrophys. 283, 51.

    Google Scholar 

  39. Unwin, S.C., Cohen, M.H., Biretta, J.A., Hodges, M.W. and Zensus, J.A.: 1989,Astrophys. J. 340, 117.

    Google Scholar 

  40. Valtaoja, E., Teräsranta, H., Lainela, M. and Terrikorpi, P.: 1992, in: E. Valtaoja and M. Valtonen (eds.),Variability of Blazars, Cambridge University Press, Cambridge, p. 70.

    Google Scholar 

  41. Zhang, F.J. and Bååth, L.B.: 1990,Astron. Astrophys. 236, 47.

    Google Scholar 

  42. Zhang, F.J. and Bååth, L.B.: 1991,Monthly Notices Roy. Astron. Soc. 248, 566.

    Google Scholar 

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Authors and Affiliations

  1. Shanghai Observatory, Chinese Academy of Sciences, 200030, Shanghai, China

    F. J. Zhang

  2. Center for Imaging Technologies, Halmstad University, Sweden

    L. B. Bååth

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Zhang, F.J., Bååth, L.B. Viewing angles in some selected BL Lac objects. Astrophys Space Sci 235, 195–205 (1996). https://doi.org/10.1007/BF00644440

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