相关论文: Imaging and variability studies of CTA~102 during …
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…
Multi-frequency (4.6, 5, 5.5, 8, 8.8, 13, 15, 22 & 43 GHz) polarization observations of 6 "blazars" were obtained on the American Very Long Baseline Array (VLBA) over a 24-hr period on 2 July 2006. Observing at several frequencies,…
Blazars are highly variable active galactic nuclei which emit radiation at all wavelengths from radio to gamma-rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies and it also varies…
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…
Long-lasting, very bright multiwavelength flares of blazar jets are a curious phenomenon. The interaction of a large gas cloud with the jet of a blazar may serve as a reservoir of particles entrained by the jet. The size and density…
We investigate the temporal variability of polarization of synchrotron radiation from blazar jets. Multiwavelength observations revealed high-amplitude rotations of the electric vector position angle (EVPA), both in the optical and in the…
Quasi-periodic fluctuations in the light curves of blazars can provide insight into the underlying emission process. This type of flux modulation hints at periodic physical processes that result in emission. CTA 102, a flat spectrum radio…
We present radio-to-optical data taken by the WEBT, supplemented by VLBA and RXTE observations, of 3C 279. Our goal is to use this extensive database to draw inferences regarding the physics of the relativistic jet. We assemble…
We have used single-dish centimeter-band, multi-frequency linear polarization and total flux density monitoring observations obtained by UMRAO at 14.5, 8, and 4.8 GHz during gamma-ray flaring to constrain propagating shock-in-jet models;…
PG 1553+113 is the first blazar showing an approximately two-year quasi-periodic pattern in its gamma-ray light curve. Such quasi-periodicity might have a geometrical origin, possibly related to the precessing nature of the jet, or could be…
Context. The origin of blazar variability, seen from radio up to gamma rays, is still a heavily debated matter and broadband flares offer a unique testbed towards a better understanding of these extreme objects. Such an energetic outburst…
We present Fermi-LAT and multi-frequency, multi-epoch VLBA data for the TeV blazar Mrk421. We collected the data during a long and intensive multi-frequency campaign in 2011. We study the gamma-ray light curve, the photon index evolution…
(Abridged) We investigate the flux density variability and changes in the parsec-scale radio structure of the flat spectrum radio quasar PKS 1510-089. This source was target of multi-epoch VLBI and Space-VLBI observations at 4.8, 8.4 and 22…
The connection between $\gamma$-ray flares and blazars is a topic of active research, with few sources exhibiting distinct enough such outbursts to be able to conclusively connect them to features in their jet morphology. Here we present an…
We present a model of blazar variability that can both reproduce smooth large polarization angle swings, and at the same time allow for the seemingly random behaviour of synchrotron fluxes, polarization fraction and, occasionally, $\pi$/2…
We have carried out the Gaussian model-fitting to the 15 GHz VLBA cores for a sample of blazars from the MOJAVE database, analyzed the correlations in the model-fitted parameters and studied the variability properties for different group of…
CTA 102, classified as a flat spectrum radio quasar at z=1.037, produced exceptionally bright optical flare in 2012 September. Following Fermi-LAT detection of enhanced gamma-ray activity, we densely monitored this source in the optical and…
We present four high dynamic range, dual-circular polarization, Very Long Baseline Array (VLBA) observations at 22 GHz of Markarian 421, taken throughout the year following the source's unprecedented gamma-ray high state in early 2001.…
We present results of a VLBA multi-frequency study of the pc-scale twin jet in NGC1052. We observed this object at epoch 1998.99 with the VLBA at 5, 8.4, 22 and 43 GHz both in total and linearly polarized intensity. The spectral analysis…
We present the first 86 GHz VLBI observations of the radio galaxy 3C~120, together with contemporaneous 43 and 22 GHz polarimetric VLBA observations. The very high angular resolution obtained at 86 GHz provides an upper limit to the size of…