We have completed a program of monitoring of a sample of gamma-ray blazars with the VLBA at 22 and 43~GHz. The population of bright gamma-ray blazars can be classified as highly superluminal, with apparent speeds as high as about 40c. However, the majority of sources that reveal moving components also contains features which show no motion with respect to the core over the duration of our VLBA observations. This implies that stationary hot spots are a common characteristic of compact relativistic jets. Analysis of the coincidence of times of high gamma-ray flux and ejections of superluminal components from the VLBI core establishes a statistical association between the ejection of radio knots and high states of gamma-ray emission in blazars. This correlation should be confirmed through intensive VLBI monitoring when such missions as AGILE and GLAST will operate.
Blazar Astrophysics with BeppoSAX and Other Observatories
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