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Paper: A Multi-Frequency VLBI Total Intensity and Polarization Study of the BL Lacertae Object 0716+714
Volume: 144, Radio Emission from Galactic and Extragalactic Compact Sources, IAU Colloquium 164
Page: 173
Authors: Kovalev, Y. Y.; Gabuzda, D. C.; Krichbaum, T. P.; Alef, W.; Witzel, A.
Abstract: New polarization-sensitive global VLBI and VLBA images of the BL Lacertae object 0716+714 at 6 cm (1991.4) and 3.6 cm/1.3 cm (1994.2) are presented. The source shows a compact, one-sided core-jet structure in structural position angle ~13 degrees. The 3.6 cm total intensity image shows the jet beginning to curve toward the arcsecond-scale structure, which lies in position angle ~ -45 degrees. Comparison with previously published data suggests that the apparent velocity of a 6 cm jet component is >1.09 +/- 0.15 c, if the red shift of 0716+714 is z>0.3. Linear polarization from the VLBI core was detected at all three frequencies; in addition, polarization from the innermost jet component was detected at 1.3 cm. This compact jet polarization appears to be quite high, ~50%, and to be aligned with the jet direction, which can be understood if it is a transverse shock. The VLBI core polarization at our earlier epoch was perpendicular to the VLBI jet direction, but had rotated to align with the jet direction by the later epoch, about a year later. This rotation may indicate the imminent birth of a new VLBI component (shock).
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