Abstract
We present previously unpublished circular polarization (cp) measurements at 4.8 and 8.0 GHz made with the University of Michigan 26-meter prime focus telescope during 1978–1984 and results of a new observational program during the past two years. Based on the preliminary analysis of our recent data, eight sources were detected at 4.8 GHz with average degrees of cp ranging from ≤ 0.1% to ≥ 1%.The results are compared with observations at other frequencies and with linear polarization and total flux density variability in the sources. The behavior of the cp variability observed to date is consistent with stochastic variations produced by mode conversion in transient, opaque emitting regions in the sources. The observed sign changes observed between different epochs and different frequencies are not consistent with the hypothesis that sources maintain a fixed handedness of cp.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bower, G.C., Falcke, H. and Backer, D.C.: 1999, Detection of circular polarization in the galactic center black hole candidate Sagittarius A*, The Astrophysical Journal Letters 523, L29-L32.
Bower, G.C., Falcke, H., Sault, R.J. and Backer, D.C.: 2002, The spectrum and variability of circular polarization in Sagittarius A* from 1.4 to 15 GHz, The Astrophysical Journal 571, 843-855.
Hodge, P.E. and Aller, H.D.: 1977, Variations in the circular polarization of 3C 84 and 3C 273 at 8 GHz, The Astrophysical Journal 211, 669-674.
Homan, D.C. and Wardle, J.F.C.: 1999, Detection and measurement of parsec-scale circular polarization in four AGNS, The Astrophysical Journal 118, 1942-1962.
Homan, D.C., Attridge, J.C. and Wardle, J.F.C.: 2001, Parsec-scale circular polarization observations of 40 blazars, The Astrophysical Journal 556, 113-120.
Jones, T.W. and O'Dell, S.L.: 1997a, Transfer of polarized radiation in self-absorbed synchrotron sources. I. Results for a homogeneous source, The Astrophysical Journal 214, 522-539.
Jones, T.W. and O'Dell, S.L.: 1977b, Transfer of polarized radiation in self-absorbed synchrotron sources. II. Treatment of inhomogeneous media and calculation of emergent polarization, The Astrophysical Journal 215, 236-246.
Komesaroff, M.M., Roberts, J.A., Milne, D.K., Rayner, P.T. and Cooke, D.T.: 1984, Circular and linear polarization variations of compact radio sources, MNRAS 208, 409-425.
Legg, M.P.C. and Westfold, K.C.: 1968, Elliptical polarization of synchrotron radiation, The Astrophysical Journal 154, 499-514.
Macquart, J.-P., Kedziora-Cudczer, L., Rayner, D.P. and Jauncey, D.L.: 2000, Strong, variable circular polarization in PKS 1519-273, The Astrophysical Journal 538, 623-627.
Macquart, J.-P. and Melrose, D.B.: 2000, Scintillation-induced circular polarization in pulsars and quasars, The Astrophysical Journal 545, 798-806.
Rayner, D.P., Norris, R.P. and Sault, R.J.: 2000, Radio circular polarization of active galaxies, MNRAS 319, 484-496.
Sault, R.J. and Macquart, J.-P.: 1999, Confirmation and analysis of circular polarization from Sagittarius A*, The Astrophysical Journal Letters 526, L85-L88.
Wardle, J.F.C., Homan, D.C., Ojha, R. and Roberts, D.H.: 1998, Electron-positron jets associated with the quasar 3C 279, Nature 395, 457-461.
Weiler, K.W. and de Pater, I.: 1983, A catalogue of high accuracy circular polarization measurements, The Astrophysical Journal Supplement 52, 293-327.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Aller, H.D., Aller, M.F. & Plotkin, R.M. Circular Polarization Variability in Extragalactic Sources on Time Scales of Months to Decades. Astrophysics and Space Science 288, 17–28 (2003). https://doi.org/10.1023/B:ASTR.0000004990.22510.53
Issue Date:
DOI: https://doi.org/10.1023/B:ASTR.0000004990.22510.53