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Session 84 - QSOs and BL Lacs.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
In quasars with strong radio cores, the inverse-Compton process is believed to be the dominant source of X-ray emission. VLBI imaging reveals compact features in the parsec-scale jets which simple models predict to be the origin of the X-rays. The quasar 3C345 (z = 0.595) is one of the best-studied, with VLBI imaging at several radio frequencies, at intervals of a few months. The well-known parsec-scale jet appears to be one-sided due to Doppler boosting, and contains superluminal components (v \approx 4 c within about 5 pc of the nucleus). From our VLBI images we can build a complete picture of the evolution of the flux densities, turnover frequencies, and angular sizes of the brightest compact components in the jet -- those which are most likely to generate significant X-ray emission via the synchrotron self-Compton process.
By combining VLBI imaging with ROSAT PSPC data (0.2 - 2 keV) from three epochs during 1990 - 1993, we study variability\/ in the expected X-ray emission. 3C345 is the first AGN for which enough data exist for this comparison at multiple epochs, since we can reliably interpolate the VLBI data to the X-ray epochs. We present the results of calculations of the inverse-Compton emission, constrained by the measured kinematic and physical parameters of the jet. The bulk Lorentz factor of the jet and its angle to the line of sight are the most important derived kinematic quantities; we show how the X-ray data constrain changes in these quantities.
Program listing for Wednesday