Related papers: Can long-term periodic variability and jet helicit…
VLBI observations have shown that the parsec-jet of 3C 345 is formed by several components, ejected from the core with superluminal velocities and travelling along bent trajectories on the plane of the sky. We interpret the differences in…
The nearby radio galaxy M87 offers a unique opportunity to explore the connections between the central supermassive black hole and relativistic jets. Previous studies of the inner region of M87 revealed a wide opening angle for the jet…
We describe a scenario to explain blazar periodicities with timescales of $\sim$ few years. The scenario is based on a binary super-massive black hole (SMBH) system in which one of the two SMBH carries a jet. We discuss the various…
We consider the periodic modulation of emission from jets in blazar-type sources. A differential Doppler boosting origin, associated with the helical motion of a radiating component, is analyzed for different periodic driving sources…
The ``central engine'' of AGN is thought to be powered by accretion on a central nucleus believed to be a super-massive black hole. The localization and exact mechanism of the energy release in AGN are still not well understood. We present…
Variations of the optical continuum emission in the radio galaxy 3C 390.3 are compared to the properties of radio emission from the compact, sub-parsec-scale jet in this object. We showed that very long-term variations of optical continuum…
The recent discovery of a roughly simultaneous periodic variability in the light curves of the BL Lac object PG 1553+113 at several electromagnetic bands represents the first case of such odd behavior reported in the literature. Motivated…
The blazar AO 0235+164 is a key source for studying the interplay between multi-wavelength variability in its light curves and changes in the position angles and apparent velocities of its parsec-scale jet components. In this work, we…
Relativistic outflows represent one of the best-suited tools to probe the physics of AGN. Numerical modelling of internal structure of the relativistic outflows on parsec scales provides important clues about the conditions and dynamics of…
Context. OJ287 is a quasar with a quasi-periodic optical light curve, with the periodicity observed for over 120 years. This has lead to a binary black hole model as a common explanation of the quasar. The radio jet of OJ287 has been…
Results are presented from long term VLBI monitoring of the parsec-scale radio jet in 3C120, primarily at 5 and 1.7 GHz. Numerous superluminal features are followed, some over large fractional distances from the core. The speeds of the…
Many jets exhibit twisted helical structures. Where superluminal motions are detected, jet orientation and pattern/flow speed are considerably constrained. In this case modeling efforts can place strong limits on conditions in the jet and…
BL Lacertae is the prototype of the BL Lac class of active galactic nuclei, exhibiting intensive activity on parsec (pc) scales, such as intense core variability and multiple ejections of jet components. In particular, in previous works the…
Observational constraints on the configuration of the black hole (BH)-accretion disk-jet system are crucial to understanding BH spin, accretion disk physics, and jet formation. The recently reported variation in the M87 jet position angle…
Supermassive black hole binaries may be detectable by an upcoming suite of gravitational wave experiments. Their binary nature can also be revealed by radio jets via a short-period precession driven by the orbital motion as well as the…
Very long baseline interferometric observations of the radio galaxy 3C 120 show a systematic presence of gradients in Faraday rotation and degree of polarization across and along the jet. These are revealed by the passage of multiple…
The long-term variability of the multiwavelength blazar emission can be interpreted in terms of orientation variations of a helical, inhomogeneous, non-thermally emitting jet, possibly caused by the orbital motion of the parent black hole…
We present a possible scenario for the ejection of a superluminal component in the jet of the Broad Line Radio Galaxy 3C111 in early 1996. VLBI observations at 15 GHz discovered the presence of two jet features on scales smaller than one…
In this paper we use radio polarimetric observations of the jet of the nearby bright quasar 3C\,345 to estimate the fluid velocity on kiloparsec scales. The jet is highly polarized, and surprisingly, the electric vector position angles in…
The mechanism and the region of generation of variable continuum emission are poorly understood for radio-loud AGN because of a complexity of the nuclear region. High-resolution radio VLBI (very long baseline interferometry) observations…