A connection between $\gamma$-ray and parsec-scale radio flares in the
  blazar 3C 273
  We present a comprehensive 5-43 GHz VLBA study of the blazar 3C 273 initiated
after an onset of a strong $\gamma$-ray flare in this source. We have analyzed
the kinematics of new-born components, light curves, and position of the
apparent core to pinpoint the location of the $\gamma$-ray emission. Estimated
location of the $\gamma$-ray emission zone is close to the jet apex, 2 pc to 7
pc upstream from the observed 7 mm core. This is supported by ejection of a new
component. The apparent core position was found to be inversely proportional to
frequency. The brightness temperature in the 7 mm core reached values up to at
least $10^{13}$ K during the flare. This supports the dominance of particle
energy density over that of magnetic field in the 7 mm core. Particle density
increased during the radio flare at the apparent jet base, affecting
synchrotron opacity. This manifested itself as an apparent core shuttle along
the jet during the 7 mm flare. It is also shown that a region where optical
depth decreases from $\tau\sim1$ to $\tau<<1$ spans over several parsecs along
the jet. The jet bulk flow speed estimated at the level of 12c on the basis of
time lags between 7 mm light curves of stationary jet features is 1.5 times
higher than that derived from VLBI apparent kinematics analysis.
