Multiepoch Very Long Baseline Array Observations of EGRET‐detected Quasars and BL Lacertae Objects: Connection between Superluminal Ejections and Gamma‐Ray Flares in Blazars

Abstract

We examine the coincidence of times of high c-ray Ñux and ejections of superluminal components from the core in EGRET blazars based on a Very Long Baseline Array (VLBA) monitoring program at 22 and 43 GHz from 1993 November to 1997 July. In 23 cases of c-ray Ñares for which sufficient VLBA data exist, 10 of the Ñares (in eight objects) fall within 1 p uncertainties of the extrapolated epoch of zero separation from the core of a superluminal radio component. In each of two sources (0528]134 and 1730[130), two successive c-ray Ñares were followed by the appearance of new superluminal components. We carried out statistical simulations that show that if the number of coincidences is º10, the radio and c-ray events are associated with each other at greater than 99.999% conÐdence. Our analysis of the observed behavior, including variability of the polarized radio Ñux, of the sources before, during, and after the c-ray Ñares suggests that the c-ray events occur in the superluminal radio knots. This implies that the c-ray Ñares are caused by inverse Compton scattering by relativistic electrons in the parsec-scale regions of the jet rather than closer to the central engine.