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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).
The author(s) of this abstract have provided an email address for comments about the abstract: gpiner@whittier.edu