Hostname: page-component-76fb5796d-zzh7m Total loading time: 0 Render date: 2024-04-29T03:15:37.913Z Has data issue: false hasContentIssue false
  • English
  • Français

The Time Scale of Decimetre Flux Density Variations

Published online by Cambridge University Press:  25 April 2016

W. B. McAdam
W. B. McAdam*
Affiliation:
School of Physics, University of Sydney
Get access Rights & Permissions [Opens in a new window]

Extract

One of the critical parameters for a theory of emission from QSOs is the time scale of the variations in this emission. For many sources, changes occur faster than the light travel time across the source disk size as determined by VLBI observations. If the decimetre flux density is assumed to come from a small core, appropriate to the time scale of its variations then the brightness temperature must be far greater than ~ 1012 K allowed by the incoherent synchrotron process. These difficulties have been examined (Jones and Burbidge 1973; Burbidge and Stein 1975) using the QSO 2251 + 158 (3C454.3) as an example against which to test the theory. In this paper, I examine the time scale of the variations in 46 sources and show that most of these vary significantly within 2 years. The most rapid changes are in the QSOs 0736 + 017 and 1504–166 which have changed 40% within a few months — an order of magnitude faster than 2251 + 158.

Type
Extra-galactic
Information
Publications of the Astronomical Society of Australia , Volume 3 , Issue 4 , 1978 , pp. 283 - 285
Copyright
Copyright © Astronomical Society of Australia 1978

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Burbidge, G. R., and Stein, W. A. Comments Astrophys., 6, 87(1975).Google Scholar
Conklin, E. K., Bull. Am. Astron. Soc, 7, 437 (1975).Google Scholar
Cotton, W. D., Astrophys. J., 204, L63 (1976).CrossRefGoogle Scholar
Haves, P., Conway, R. G., and Stannard, D., Mon. Not. R. Astron. Soc., 169, 117(1974).CrossRefGoogle Scholar
Hunstead, R. W., Astrophys. Lett., 12, 192 (1972).Google Scholar
Hunstead, R. W., Murdoch, H. S., and Shobbrook, R. R., Mon. Not. R. Astron. Soc. (in press, 1978).Google Scholar
Jones, T. W., and Burbidge, G. R., Astrophys. J., 186, 791 (1973).CrossRefGoogle Scholar
McAdam, W. B., Proc. Astron. Soc. Aust., 3, 86 (1976).CrossRefGoogle Scholar
Malumyan, V. G., and Sanamyan, V. A., Astrophys. AN. USSR, 11, 153; ibid., 699 (1975).Google Scholar
Stannard, D., and Bentley, M., Mon. Not. R. Astron. Soc, 180, 703 (1977).CrossRefGoogle Scholar