出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present the results of a multi-frequency analysis of the structural variability in the parsec-scale
jet of the blazar S5 1803+784. More than 90 epochs of observations at 6 frequencies from 1.6
GHz up to 22 GHz have been combined and analyzed. We discuss an alternative jet model for
the source. In contrast to previously discussed motion scenarios for S5 1803+784, we find that
the jet structure within 12 mas of the core can most easily and plausibly be described by seven
“oscillating” jet features. We find that the parameters of jet features, such as core separation,
position angle and flux density, change in a periodic way with a timescale of about 4 years. We
also find evidence for a correlation between these parameters and the total flux density variations.
We suggest a scenario incorporating a periodic form of motion (e.g. rotation, precession), with a
non-negligible geometrical contribution to explain the observational results.
