Related papers: Polarization and Variations of BL Lacertae Objects

Typical blazars seem to be associated with FR I and FR II radio galaxies and radio-loud quasars. However, what happens at lower powers? Do blazars exist in low-luminosity AGN or do they exist in radio-quiet AGN? A recent detection of…

In this lecture note, we make the case for new (spectro)polarimetric measurements of "changing-look" AGNs (CLAGNs), a subclass of the AGN family tree that shows long-term (months to years) large flux variability associated with the…

The extremes of Active Galactic Nuclei (AGN) variability offer valuable new insights into the drivers and physics of AGN. We discuss some of the most extreme cases of AGN variability; the highest amplitudes, deep minima states, extreme…

We present a radio/optical study of a sample of BL Lac objects at arcsecond and milliarcsecond resolution. The sample consists of 30 nearby (z<0.2) BL Lacs, mostly X-ray selected. These nearby objects are weak in the radio, yet we have…

BL Lacertae is a unique blazar for which the X-ray band can cover either the synchrotron or the inverse Compton, or both parts of the broadband spectral energy distribution. In the latter case, when the spectral upturn is located in the…

We perform a multi-band statistical analysis of core-dominated superluminal active galactic nuclei (AGN) detected with Fermi Large Area Telescope (LAT). The detection rate of $\gamma$-ray jets is found to be high for optically bright AGN.…

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed contemporaneously by the Very Long Baseline Array (VLBA). In total, 232 sources were observed with…

We study linear polarization due to scattering of light on a cloudlet of particles, taking into account the radiation drag and the gravitational pull exerted on them by a central body. Effects of special and general relativity are included…

We carried out multi-color optical monitoring of a sample of ten blazars from 2005 to 2011. The sample contains 3 LBLs, 2 IBLs, 4 HBLs, and 1 FSRQ. Our monitoring focused on the long-term variability and the sample included nine BL Lac…

The formation of beam halos has customarily been described in terms of a particle-core model in which the space-charge field of the oscillating core drives particles to large amplitudes. This model involves parametric resonance and predicts…

We present preliminary results of JVLA wideband full polarization observations of a sample of Active Galactic Nuclei (AGN) with very high Rotation Measure (RM) values, a sign of extreme environment. Polarization properties show a complex…

The polarization state of starlight reflected by a planetary atmosphere uniquely reveals coverage, particle size, and composition of aerosols as well as changing cloud patterns. It is not possible to obtain a comparable level of detailed…

Here we report our recent results of variability studies in optical and X-ray bands of three blazars namely 3C 273, PKS 2155 - 304 and BL Lacertae with XMM-Newton. We found large amplitude optical to X-rays variability in 3C 273, and PKS…

We present the results of extensive multi-band intra-night optical monitoring of BL Lacertae during 2010--2012. BL Lacertae was very active in this period and showed intense variability in almost all wavelengths. We extensively observed it…

The long-term optical and infrared color variability of blazars has been investigated with the SMARTS monitoring data. The sample in this study consists of 49 flat spectrum radio quasars and 22 BL Lac objects. The fractional variability…

The current status of leptonic jet models for blazars is reviewed. Differences between the quasar and BL-Lac subclasses of blazars may be understood in terms of the dominance of different radiation mechanisms in the gamma-ray regime.…

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey (VIPS). This large, flux-limited sample of active…

The \gamma-ray loud blazars (flat spectrum radio quasars--FSRQs and BL Lacertae objects-BLs) are very bright in the \gamma-ray bands, which is perhaps associated with a beaming effect. Therefore, one can expect that the \gamma-ray…

Elastic scattering of laser radiation due to vacuum polarization by spatially modulated strong electromagnetic fields is considered. The Bragg interference arising at a specific impinging direction of the probe wave concentrates the…

We have measured multi-band optical flux and colour variations for a sample of 12 low energy peaked blazars on short, day-to-month, timescales. Our sample contains six BL Lacertae objects and six flat spectrum radio quasars. These…