V. A. Hagen‐Thorn
A5055509150- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Particle Accelerators and Free-Electron Lasers
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Gyrotron and Vacuum Electronics Research
- Calibration and Measurement Techniques
- Astrophysics and Star Formation Studies
- Computational Physics and Python Applications
- Ionosphere and magnetosphere dynamics
- Particle physics theoretical and experimental studies
- Scientific Research and Discoveries
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Optical Polarization and Ellipsometry
- Algebraic and Geometric Analysis
St Petersburg University
2013-2023
Institute of Applied Astronomy
2005-2022
Isaac Newton Institute
2006-2016
Guangzhou University
2003
Astronomical Institute of the Slovak Academy of Sciences
2002
Pushkin Leningrad State University
1987-2000
We present results from monitoring the multi-waveband flux, linear polarization, and parsec-scale structure of quasar PKS 1510-089, concentrating on eight major gamma-ray flares that occurred during interval 2009.0-2009.5. The peaks were essentially simultaneous with maxima at optical wavelengths, although flux ratio two wavebands varied by an order magnitude. polarization vector rotated 720 degrees a 5-day period encompassing six these flares. This culminated in very bright, roughly 1 day,...
We combine time-dependent multi-waveband flux and linear polarization observations with sub-milliarcsecond-scale polarimetric images at lambda=7mm of the BL Lacertae-type blazar OJ287 to locate gamma-ray emission in prominent flares jet source >14pc from central engine. demonstrate a highly significant correlation between strongest millimeter-wave through Monte-Carlo simulations. The two reported peaks occurred near beginning major mm-wave outbursts, each which is associated maximum...
We analyze the behavior of parsec-scale jet quasar 3C 454.3 during pronounced flaring in 2005–2008. Three major disturbances propagated down along different trajectories with Lorentz factors Γ > 10. The show a clear connection millimeter-wave outbursts, 2005 May/June, 2007 July, and December. High-amplitude optical events R-band light curve precede peaks outbursts by 15–50 days. Each outburst is accompanied an increase X-ray activity. associate propagation superluminal knots derive location...
We analyze the multifrequency behavior of quasar 3C 454.3 during three prominent \gamma-ray outbursts: 2009 Autumn, 2010 Spring, and Autumn. The data reveal a repeating pattern, including triple flare structure, in properties each outburst, which implies similar mechanism(s) location for all events. multi-frequency indicates that lower frequency events are co-spatial with outbursts, although emission varies on shortest timescales. determine variability from UV to IR wavelengths an outburst...
We present the results of extensive multi-waveband monitoring blazar 3C~279 between 1996 and 2007 at X-ray energies (2-10 keV), optical R band, 14.5 GHz, as well imaging with Very Long Baseline Array (VLBA) 43 GHz. In all bands power spectral density corresponds to "red noise" that can be fit by a single law over sampled time scales. Variations in flux three wavebands are significantly correlated. The delay high low frequency changes substantially on scales years. A major multi-frequency...
We present the results of optical (R band) photometric and polarimetric monitoring Very Long Baseline Array (VLBA) imaging blazar S5 0716+714 along with Fermi gamma-ray data during a multi-waveband outburst in 2011 October. analyze total polarized intensity images obtained VLBA at 43 GHz after outburst. Monotonic rotation linear polarization vector rate >50 degrees per night coincided sharp maximum flux. At same time, within uncertainties, new superluminal knot appeared, an apparent speed...
We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and γ-ray wavelengths the BL Lacertae object AO 0235+164. analyze timing multi-waveband variations in flux linear polarization, as well changes Very Long Baseline Array images λ = 7 mm with ∼0.15 milliarcsec resolution. The association events different wavebands is confirmed high statistical significance by probability arguments Monte Carlo simulations. A series sharp peaks optical pronounced maximum...
We present UBVRI light curves of BL Lacertae from May 2000 to January 2001, obtained by 24 telescopes in 11 countries. More than 15000 observations were performed that period, which was the extension Whole Earth Blazar Telescope (WEBT) campaign originally planned for July-August 2000. Rapid flux oscillations are all time, involving variations up a few tenths mag on hour time scales, and witnessing an intense intraday activity this source. Colour indexes have been derived coupling highest...
The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. maximum brightness detected was R = 12.0, which represents the most luminous state thus far observed (M_B ~ -31.4). In order to follow emission behaviour of source detail, a large multiwavelength campaign organized by Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR monitoring performed several bands. ToO pointings Chandra INTEGRAL satellites provided...
BL Lacertae has been the target of four observing campaigns by Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present $UBVRI$ light curves obtained WEBT from 1994 to 2002, including last, extended Lac 2001 campaign. A total about 7500 optical observations performed 31 telescopes Japan Mexico have collected, be added $\sim 15600$ Campaign 2000. All these data allow one follow source emission behaviour with unprecedented detail. The analysis colour indices reveals that...
Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability flux at all wavebands. Its variations polarization are quite complex therefore require intensive monitoring observations multiple wavebands to characterise interpret observed changes.
Aims. Since the CGRO operation in 1991–2000, one of primary unresolved questions about blazar γ-ray emission has been its possible correlation with low-energy (in particular optical) emission. To help answer this problem, Whole Earth Blazar Telescope (WEBT) consortium organized GLAST-AGILE Support Program (GASP) to provide optical-to-radio monitoring data be compared detections by AGILE and GLAST satellites. This new WEBT project started early September 2007, just before a strong detection...
We report on the multi-wavelength observations of PKS 1510-089 (a flat spectrum radio quasar (FSRQ) at z = 0.361) during its high activity period between 2008 September and 2009 June. During this 11 month period, source was characterized by a complex variability optical, UV, γ-ray bands, timescales down to 6–12 hr. The brightest isotropic luminosity, recorded March 26, ≃2 × 1048 erg s−1. in Fermi Large Area Telescope energy range shows mild curvature described well log-parabolic law, can be...
We report on 18 months of multiwavelength observations the blazar 3C 454.3 (Crazy Diamond) carried out in July 2007-January 2009. show results AGILE campaigns which took place May-June 2008, July-August and October 2008-January During May 2009 period, source average flux was highly variable, from an gamma-ray F(E>100MeV) > 200E-8 ph/cm2/s to F(E>100MeV)~80E-8 The spectrum between 100 MeV 1 GeV can be fit by a simple power law (Gamma_GRID ~ 2.0 2.2). Only 3-sigma upper limits derived 20-60...
Context. Over the past few years, on several occasions, large, continuous rotations of electric vector position angle (EVPA) linearly polarized optical emission from blazars have been reported. These events are often coincident with high energy γ-ray flares and they attracted considerable attention, since could allow us to probe magnetic field structure in emitting region jet. The flat-spectrum radio quasar 3C 279 is one most prominent examples showing this behaviour.
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from radio to optical bands since 2004 study its emission variability properties.
We present the results of polarimetric (R-band) and multicolor photometric (BH RI J H K) observations blazar AO 0235+16 during an outburst in 2006 December. The data reveal a short timescale variability (several hours), which increases from optical to near-IR wavelengths; even shorter variations are detected polarization. flux density correlates with degree polarization, at maximum polarization electric vector tends align parsec-scale jet direction. find that variable component steady...
<i>Context. <i/>Since 2001, the radio quasar 3C 454.3 has undergone a period of high optical activity, culminating in brightest state ever observed, during 2004-2005 outburst. The Whole Earth Blazar Telescope (WEBT) consortium carried out several multifrequency campaigns to follow source behaviour.<i>Aims. <i/>The GLAST-AGILE Support Program (GASP) was born from WEBT provide long-term continuous optical-to-radio monitoring sample <i>γ<i/>-loud blazars, operation AGILE and GLAST (now known as...
The quasar-type blazar 4C 38.41 (B3 1633+382) experienced a large outburst in 2011, which was detected throughout the entire electromagnetic spectrum. We present results of low-energy multifrequency monitoring by GASP project WEBT consortium and collaborators, as well those spectropolarimetric/spectrophotometric at Steward Observatory. also analyse high-energy observations Swift Fermi satellites. In optical-UV band, several indicate that there is contribution from QSO-like emission...
We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright γ-ray outburst detected by Fermi Large Area Telescope in 2012 September–October when source reached flux F>100 MeV = 5.2 ± 0.4 × 10−6 photons cm−2 s−1. At same time, displayed unprecedented optical and near-infrared (near-IR) outburst. evolution parsec-scale jet with ultra-high angular resolution through sequence 80 total polarized intensity Very Long Baseline Array images at 43 GHz,...
After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September–October. The flare was tracked from γ-ray to near-infrared (NIR) frequencies, including Fermi and Swift data as well photometric polarimetric observatories. An intensive Glast-Agile support programme Whole Earth Blazar Telescope (GASP–WEBT) collaboration campaign optical NIR bands, with addition previously unpublished archival extension through fall 2015, allows comparison this previous...