Kinematic Studies of the IDV Quasar S. Bernhart T. P. Krichbaum L. Fuhrmann Max-Planck-Institut fϋr Radioastronomie, Bonn

EVN Symposium, Torun Outline Introduction of Motivation and description of the observations 2cm modelfit results Summary and future work

EVN Symposium, Torun The Quasar IDV Type II source at z=1.446 Episodically varying: high variability amplitudes from 1988 to 1999 (m~3-5%) Variability ceased in 1998 (Kraus et al. 1999) and 2000, since then m~0.5%

EVN Symposium, Torun The Quasar IDV Type II source at z=1.446 Episodically varying: high variability amplitudes from 1988 to 1999 (m~3-5%) Variability ceased in 1998 (Kraus et al. 1999) and 2000, since then m~0.5% T.P. Krichbaum/L. Fuhrmann

EVN Symposium, Torun Change of scintillating medium Flux decrease of scintillating component Jet precession Reduced IDV caused by component ejection: core size becomes larger than scattering size (typically ~0.05 – 0.07 mas for 0917, Rickett et al. 1995) -> quenched scintillation – could be possible explanation for 1998 (Krichbaum et al. 2002, Fuhrmann et al. 2002, Fuhrmann 2004) VLBI observations in order to find new components Possible Explanations for Reduced IDV Activity

EVN Symposium, Torun Observing Epochs VLBI: 1.3cm, 2cm, 6cm additionally: MOJAVE-2cm: VLBI-Observations at 2cm:

EVN Symposium, Torun cm modelfit maps S. Bernhart, in prep. beam x mas bpa -18° beam 0.2 x 0.2 mas

EVN Symposium, Torun Core Separation at 2cm S. Bernhart, in prep.

EVN Symposium, Torun Core Separation at 2cm Krichbaum et al. 2002/Fuhrmann 2004/Bernhart, in prep.

EVN Symposium, Torun Flux Density Monitoring S. Bernhart, in prep. time delay ~ 0.8 years between 2.8 cm and 11 cm (N. Kudryavzeva, priv. comm.)

EVN Symposium, Torun Summary New components ejected in 2000 and 2003(?) No increase in the modulation index after component ejection Hypothesis of quenched scintillation not conclusive Future Work Continue single dish monitoring Further VLBI observations in order to test also different hypotheses