The Outburst of the Blazar S5 0716+71 in 2011 October: Shock in a
  Helical Jet
  We present the results of optical (R band) photometric and polarimetric
monitoring and Very Long Baseline Array (VLBA) imaging of the blazar S5
0716+714 along with Fermi gamma-ray data during a multi-waveband outburst in
2011 October. We analyze total and polarized intensity images of the blazar
obtained with the VLBA at 43 GHz during and after the outburst. Monotonic
rotation of the linear polarization vector at a rate of >50 degrees per night
coincided with a sharp maximum in gamma-ray and optical flux. At the same time,
within the uncertainties, a new superluminal knot appeared, with an apparent
speed of ~21c. The general multi-frequency behavior of the outburst can be
explained within the framework of a shock wave propagating along a helical path
in the blazar's jet.
