VSOP and VLBA Observations of EGRET-Identified Active Galactic Nuclei

Abstract

We made high-resolution VLBI observations of six southern gamma-ray loud quasars, which were identified by EGRET (Energetic Gamma-Ray Experiment Telescope) on-board gamma-ray detector, with VSOP (VLBI Space Observatory Programme) and the VLBA. All sources show a compact core-dominant structure and the core component of three sources has a brightness temperature greater than 10 12 K in the source's rest frame. Having combined our observations with previous results we conclude that two sources out of three (PKS 0336−019 and PKS 0537−441) have small jet viewing angles. Based on two-epoch VSOP observations, we found that also the third source, PKS 1741−038, has the jet viewing angle smaller than 4.8 • . On the other hand, an observation of PKS 1622−297, exhibiting a spectacular GeV gamma-ray flare, shows rather lower Doppler factor and larger jet viewing angle than those of other gamma-ray-loud active galactic nuclei (AGNs). We examine the gamma-ray emission mechanism in the light of these observations. The 8th European VLBI Network Symposium