Free access article

A&A 435, 497-506 (2005)
DOI: 10.1051/0004-6361:20042427

The extreme flare in III Zw 2:

Evolution of a radio jet in a Seyfert galaxy

A. Brunthaler^{1, 2}, H. Falcke^{3, 4}, G. C. Bower⁵, M. F. Aller⁶, H. D. Aller⁶ and H. Teräsranta<sup>7

1</sup>  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
²  Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
    e-mail: brunthaler@jive.nl
³  ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands
⁴  Department of Astrophysics, Radboud Universiteit Nijmegen, Postbus 9010, 6500 GL Nijmegen, The Netherlands
⁵  Radio Astronomy Laboratory, University of California at Berkeley, 601 Campbell Hall, CA 94720, USA
⁶  University of Michigan, Astronomy Department, Ann Arbor, MI 48109-1090, USA
⁷  Metsähovi Radio Observatory, Helsinki University of Technology, Metsahovintie 114, 02540 Kylmälä, Finland

(Received 24 November 2004 / Accepted 24 January 2005 )

Abstract
A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise to a few as. The spectral and spatial evolutions of the source are closely linked, and these observations allowed us to study a textbook example of a synchrotron self-absorbed jet in great detail. We observed a phase where the jet gets frustrated with neither expansion nor spectral evolution. Then the jet breaks free and starts to expand with apparent superluminal motion. This expansion is accompanied by a strong spectral evolution. The results are a good confirmation of synchrotron theory and equipartition for jets.

Key words: galaxies: active -- galaxies: individual: III Zw 2 -- galaxies: jets -- galaxies: Seyfert

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© ESO 2005

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