Astron. Astrophys. 333, 445-451 (1998)

VLBI polarization observations of the rapidly variable BL Lacertae object BL 0716+714

D.C. Gabuzda ¹, Y.Y. Kovalev ^{1, 2}, T.P. Krichbaum ³, W. Alef ³, A. Kraus ³, A. Witzel ³ and A. Quirrenbach <sup>4

1</sup> Astro Space Centre, Lebedev Physical Insitute, Leninsky Pr. 53, 117924 Moscow, Russia
² Sternberg Astronomical Institute, Moscow State University, 13 Universitetsky Pr., 119899 Moscow, Russia
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
⁴ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, Postfach 1603, D-85470 Garching bei München, Germany

Received 20 October 1997 / Accepted 6 January 1998

Abstract

New polarization-sensitive global VLBI and VLBA images of the BL Lacertae object BL 0716+714 at 6 cm (1991.43) and 3.6 cm/1.3 cm (1994.22) are presented. The source shows a compact, one-sided core-jet structure in structural position angle . Comparison with previously published data suggests that the apparent velocity of a 6 cm jet component is , if the redshift of BL 0716+714 is ( km s^-1 Mpc ^-1 ; ). 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 is quite high, , and is aligned with the jet direction, suggesting it is a transverse shock. The VLBI core polarization at our earlier epoch was perpendicular to the VLBI jet direction, but aligned with the jet direction at the later epoch, about three years later. The available evidence suggests that the very rapid variability that is sometimes observed in BL 0716+714 occurs on more compact scales than those imaged by our VLB array.

Key words: BL Lacertae objects: individual: BL 0716+714 galaxies: jets radio continuum: galaxies polarization

Send offprint requests to: D.C. Gabuzda

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Contents

• 1. Introduction
• 2. Observations
• 3. Results
  • 3.1.  cm, 1991.43 (June 6)
  • 3.2.  cm, 1994.22 (March 21)
  • 3.3.  cm, 1994.22
• 4. Discussion
  • 4.1. Spectral indices
  • 4.2. VLBI core polarization
  • 4.3. Superluminal motion in BL 0716+714 - Barely
  • 4.4. The angle to the line of sight of the compact jet in BL 0716+714
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: April 20, 1998
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