Abstract
Cannon and Penston1 have reported observations of the rapid optical fluctuations of the quasi-stellar object 3C 446. These add further to the study of rapid variations discovered in this object by Sandage2 and followed in 1966 by Kinman, Lamla and Wirtanen3. Variations of this kind lead to the conclusion that the region which gives rise to the fluctuation is very small, and in general it is found that for this region R ⩽ c τ, where τ is the period over which a flux change has occurred. A detailed discussion of this result has been given by Terrell4 and others. These limitations lead to very restrictive conditions on the possible models of quasi-stellar objects which arise largely from the high radiation density that must be present in the continuum source. The upper limits to the sizes which have been used range from light months to light days (∼1017 — 1015 cm) and the corresponding lower limits to the energy densities are then in the range 10–105 erg/cm3 if the quasi-stellar objects are at cosmo-logical distances, and 10−3–10 ergs/cm3 if the objects lie at distances ∼ 10 megaparsec (Mpc). If the objects are at cosmological distances, then this radiation field is so intense that it would be self-destructive, whether it arises by the synchrotron process or from the inverse Compton process5,8. The difficulties that are encountered in arriving at satisfactory models, if the quasi-stellar objects are at cosmological distances, have been considered by Hoyle, Burbidge and Sargent5. Attempts to evade or to minimize these difficulties if the objects are at cosmological distances have been made by Rees6, by Woltjer7, and by Hoyle and Burbidge8, and they require that the radiating blobs are moving at relativistic speeds and/or that there is a large degree of directivity in the streams of relativistic electrons. If the quasi-stellar objects are much closer, the radiation density is accordingly reduced and the problems are less severe.
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Cannon, R. D., and Penston, M. V., Nature, 214, 256 (1967).
Sandage, A. R., Intern. Astro. Union Circ. No. 1961 (1966). Sandage, A. R., Westphal, J. A., and Strittmatter, P. A., Astrophys. J., 142, 322 (1966).
Kinman, T. D., Lamla, E., and Wirtanen, C. A., Astrophys. J., 146, 964 (1966).
Terrell, J., Astrophys. J., 147, 827 (1967).
Hoyle, F., Burbidge, G. R., and Sargent, W. L. W., Nature 209 751 (1966).
Rees, M. J., Nature, 211, 468 (1966).
Woltjer, L., Astrophys. J., 146, 597 (1966).
Hoyle, F., and Burbidge, G. R., Nature, 212, 1223 (1966).
Burbidge, G. R., Astrophys. J., 147, 851 (1967).
Burbidge, G. R., and Burbidge, E. M., Astrophys. J., 148, L107 (1967).
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BURBIDGE, G. Optical Variations in 3C 446. Nature 214, 1213 (1967). https://doi.org/10.1038/2141213a0
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DOI: https://doi.org/10.1038/2141213a0
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