Milliarcsecond-Scale Structure in the Gamma-Ray Loud Quasar PKS 1622−297

Abstract

Abstract We made a high-resolution VLBI observation of the gamma-ray loud quasar PKS 1622$-$297 with the HALCA spacecraft and ground radio telescopes at 5 GHz in 1998 February, almost 3 yr after the source exhibited a spectacular GeV gamma-ray flare. The source shows an elongated structure toward the west on the parsec scale. The visibility data are well modeled by three distinct components: a bright core and two weaker jet components. Comparison with previous observations confirms that the jet components have an apparent superluminal motion up to $12.1 \,h^{-1} \, c$, with the inner jet components having lower superluminal speeds. We applied the inverse Compton catastrophe model and derived a Doppler factor, $\delta$, of 2.45, which is rather lower than those of other gamma-ray loud active galactic nuclei (AGNs), suggesting that the source was in a more quiescent phase at the epoch of our observation. As an alternative probe of the subparsec-scale structure, we also present the results from multiepoch ATCA total flux monitoring, which indicate the presence of persistent intraday variability consistent with refractive interstellar scintillation. We examined the gamma-ray emission mechanism in light of these observations.