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B.G. Piner (Whittier College, Dept. of Physics and Astronomy; JPL), P.G. Edwards (ISAS), S. Fodor (Whittier College, Dept. of Physics and Astronomy; JPL), T.A. Rector (NOAO)
We present results of VLBI monitoring observations of five blazars (Mrk 421, Mrk 501, 1ES 2344+514, PKS 2155-304, and 1ES 1959+650) reported as detections by TeV \gamma-ray telescopes. For Mrk 421 and Mrk 501, we have used predominantly archival VLBI data from various sources to obtain VLBI images at 15 epochs and 9 epochs respectively. For the other three blazars, we have conducted multi-epoch observations with the NRAO VLBA. Results to date on the speeds of jet features in Mrk 421, Mrk 501 (at 5 epochs), and 1ES 2344+514 have shown the apparent speeds of the parsec-scale jets in these sources to be significantly slower than those in the GeV blazars. Here we add results on PKS 2155-304, 1ES 1959+650, and additional epochs on Mrk 501 to this comparison. These slower speeds may indicate rapid deceleration of the jets in TeV blazars between the \gamma-ray emitting scales and VLBI scales, which should be possible in an electron-positron jet with a flat electron energy index, where most of the energy is carried by the highest energy particles (Marscher 1999).
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