Non-radial motion in the TeV blazar S5 0716+714 The pc-scale kinematics
  of a BL Lac Object
  For the BL Lac object S5 0716+714 conflicting apparent velocities of jet
component motion have been reported in the literature. This object is an
intra-day variable source and suited to investigate a possible correlation
between kinematic properties and flux-density variability on different
timescales. We (re-)analyze 50 VLBI observations obtained with the VLBA at 5
different frequencies (5 to 43 GHz) between 1992.73 and 2006.32. We analyze the
jet component motion in detail taking care not only to account for motion in
the radial but also in the orthogonal direction. We study the evolution of the
jet ridge line and search for correlations between radio band light curves and
the kinematic properties of the jet components. We present an alternative
kinematic scenario for jet component motion in S5 0716+714 with apparent
stationarity of jet components (with regard to their core separation) with
time. Jet components, however, do seem to move significantly non-radially with
regard to their position angle and in a direction perpendicular to the major
axis of the jet. We discuss a possible correlation between the long-term radio
flux-density variability and the kinematics. We conclude that a geometric
contribution to the origin of the long-term variability might not be
negligible. Subluminal motion has been reported for most of the TeV blazars.
Our analysis also confirms this for S5 0716+714. This result increases the
number of TeV blazars showing apparent subluminal motion to 7.
