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G. R. Denn (Sweet Briar College), R. L. Mutel (University of Iowa), M. S. Lazarova (Sweet Briar College), C. Dreier (Oberlin College), A Helton (University of Iowa)
We report on preliminary analysis of a multi-epoch VLBA observing program to monitor the magnetic field variations in the parsec-scale radio cores of three blazars: 2202+420 (z=0.07, prototype BL Lac), 1823+568 (z=0.66, QSO?), and 1749+096 (z=0.32, BL Lac). All three were observed at epochs 2001.60 and 2002.05 at frequencies of 15.4, 22.2, and 43.2 GHz. The cores of all three objects had moderate (5% - 20%) frequency-dependent fractional polarization. BL Lac continues to show a core-jet structure and two polarized superluminal components. The source 1823+568 shows a faint southern jet and possibly multiple components. The BL Lac object 1749+096 is essentially pointlike at all frequencies and at both epochs. We present two-epoch polarization and rotation measure images of these objects as well as a position angle calibration source (the quasar 2134+004).
This work is supported by the National Science Foundation Grant AST-0206194.
The author(s) of this abstract have provided an email address for comments about the abstract: gdenn@sbc.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.