Issue |
A&A
Volume 385, Number 1, April I 2002
|
|
---|---|---|
Page(s) | 55 - 61 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020145 | |
Published online | 15 April 2002 |
Analysis of the long-term polarization behaviour of BL Lac*
1
Astronomical Institute of St. Petersburg State University, Universitetsky pr. 28, 198504 St. Petersburg, Russia
2
Isaac Newton Institute of Chile, St. Petersburg Branch, Russia
3
Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215, USA
4
Stockholm Observatory, 13336 Saltsjöbaden, Sweden
Corresponding author: V. A. Hagen-Thorn, hth@vg3823.spb.edu
Received:
29
August
2001
Accepted:
22
January
2002
An analysis is performed of polarimetric and
photometric observations of BL Lac carried out in
1969–1991 at the Astronomical Institute of St. Petersburg State
University. The distribution of polarization directions certainly
points to the existence of the preferred direction of polarization
() close to the direction of the jet observed by
VLBI. High polarization degree and colorimetric data are evidence
of the synchrotron nature of the variable source. The relative
Stokes parameters are distributed normally over some mean value.
The correlations between different parameters characterizing the
flux density and polarization of the central point source allow us
to consider that in BL Lac there is a continually acting
source of polarized radiation on which the sources with randomly
distributed polarization directions are superimposed.
Key words: BL Lac objects: individual: BL Lac / techniques: polarimetric
© ESO, 2002
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