Related papers: The jet collimation profile at high resolution in …

We analyze the parsec-scale jet kinematics from 2007 June to 2013 January of a sample of $\gamma$-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43~GHz. In a total of 1929 images, we measure apparent…

We present RadioAstron Space VLBI imaging observations of the BL Lac object S5 0716+71 made on January 3-4 2015 at a frequency of 22 GHz (wavelength $\lambda=1.3$ cm). The observations were made in the framework of the AGN Polarization Key…

We present VLA and first-epoch VLBA observations that are part of a program to study the parsec-scale radio structure of a sample of fifteen high-energy-peaked BL Lacs (HBLs). The sample was chosen to span the range of logarithmic X-ray to…

Up to now, jet kinematic studies of radio quasars have barely reached beyond the redshift range at $z>3.5$. This significantly limits our knowledge of high-redshift jets, which can provide key information for understanding the jet nature…

M87 is one of the nearest radio galaxies with a central SMBH and a prominent relativistic jet. Due to its close distance to the observer and the large SMBH mass, the source is one of the best laboratories to obtain strong observational…

High resolution radio observations remain the most direct way to study the formation and evolution of radio jets associated with the accretion onto massive black holes. We report preliminary results of our seven year VLBA observational…

M87 is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc-scales. Because of its proximity and large mass of the central black hole, it is one of the best radio sources to study jet formation. We aim at…

Blazars are beamed active galactic nuclei known for their strong multi-wavelength variability on timescales from years down to minutes. We aim to investigate the suitability of the twisting jet model presented in previous works to explain…

Optical light curves of bright BL Lac objects, in particular those having the SED synchrotron peak at frequencies lower than 10E14 Hz, are characterized by long-term trends with time scales of a few decades. These variations are probabily…

Blazars are a sub-class of quasars with Doppler boosted jets oriented close to the line of sight, and thus efficient probes of supermassive black hole growth and their environment, especially at high redshifts. Here we report on Very Long…

Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106 showing a rapid and strong gamma-ray outburst followed by high and variable flux over the next months. This…

The BL Lacertae object OJ 287 is a very unusual quasar producing a wobbling radio jet and some double-peaked optical outbursts with a possible period of about 12 yr for more than one century. This variability is widely explained by models…

We present space-based very long baseline interferometry observations of the BL Lac type object OJ 287 taken with RadioAstron at 22 GHz on April 25, 2016, in conjunction with a ground array comprising 27 radio telescopes. We detect…

We present a new centimeter polarimetric VLBI image of the BL Lac object 0735+178. This source exhibits one of the most pronounced curvatures observed in jets of AGNs, with two sharp apparent bends of 90 degrees within the inner 2…

We present VLBA observations and a statistical analysis of 5 GHz VLBI polarimetry data from 177 sources in the Caltech-Jodrell Bank flat-spectrum (CJF) survey. The CJF survey, a complete, flux-density-limited sample of 293 extragalactic…

The high-redshift quasar PMN J0909+0354 ($z=3.288$) is known to have a pc-scale compact jet structure, based on global 5-GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kpc-scale structure was studied with…

Relatively few Very Long Baseline Interferometry (VLBI) polarization observations have been carried out at 18 cm. The importance of such observations lies in their ability to reveal information about the jet magnetic ({\bf B}) field…

Since the launch of the Fermi satellite, BL Lacertae has been moderately active at gamma-rays and optical frequencies until May 2011, when the source started a series of strong flares. The exceptional optical sampling achieved by the…

We investigated the detailed inner jet structure of M87 using the Very Long Baseline Array data at 2, 5, 8.4, 15, 23.8, 43, and 86 GHz, especially focusing on the multi-frequency properties of the radio core at the jet base. First, we…

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence…