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• High frequency VLBI observations of the scatter broadened quasar TXS 200 5+403,
  K. É. Gabányi, T. P. Krichbaum, S. Britzen, U. Bach, E. Ros, A. Witzel & J. A. Zensus
  Astronomy & Astrophysics, submitted
  
  • Abstract We present a multi-epoch, multi-frequency VLBI study of the quasar TXS 2005+403 from 1992 till 2003. Using the short wavelength (15 GHz, 22 GHz and 43 GHz) observational data, we describe the evolution of the inner (10 mas) structure of the source. We propose a component identification scenario with a stationary and a moving jet feature (with the apparent superluminal speed of 2c). TXS 2005+403 showed (in the UMRAO and Mets¨ahovi monitoring surveys) significant and rather complex total flux density variations on time scales of months to years at frequencies of 5 GHz, 8 GHz, 15 GHz, 22 GHz, and 37 GHz. The most striking feature was a trough in the total flux density between 1996 and 2001, with a decrease of 50% to 60% at the shortest wavelengths. Total flux density variations in AGN can often be related to the emerging of new VLBI components. However, during almost eleven years no new components have been ejected in TXS 2005+403. We discuss this long-term flux density variation within the framework of an extreme scattering event and a source intrinsic interpretation. TXS 2005+403 is located in the Cygnus region and experiences scattering by the turbulent interstellar medium (ISM) via angular broadening. We illustrate how propagation effects influence the source image at 1.6 GHz, 5 GHz, and 8 GHz. We measured the scattering disc size of to be (75.8 +/- 3.3) mas. In addition, we report on the search for intraday variability in TXS 2005+403 with the Effelsberg 100 meter radio telescope.

Eduardo Ros ros@mpifr-bonn.mpg.de

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