The Outburst of the Blazar S40954+658 in March-April 2011
  We present the results of optical (R band) photometric and polarimetric
monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S4
0954+658, along with Fermi and gamma;-ray data during a multi-waveband outburst
in 2011 March-April. After a faint state with a brightness level R ~17.6 mag
registered in the first half of January 2011, the optical brightness of the
source started to rise and reached ~14.8 mag during the middle of March,
showing flare-like behavior. The most spectacular case of intranight
variability was observed during the night of 2011 March 9, when the blazar
brightened by ~0.7 mag within ~7 hours. During the rise of the flux the
position angle of optical polarization rotated smoothly over more than
300$\deg$. At the same time, within 1$\sigma$ uncertainty a new superluminal
knot appeared with an apparent speed of 19.0$\pm$0.3 c. We have very strong
evidence for association of this knot with the multi-waveband outburst in 2011
March-April. We also analyze the multi-frequency behavior of S4 0954+658 during
a number of minor outbursts from August 2008 to April 2012. We find some
evidence of connections between at least two more superluminal ejecta and
near-simultaneous optical flares.
