A5033095430- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Calibration and Measurement Techniques
- Particle physics theoretical and experimental studies
- Radiation Detection and Scintillator Technologies
- Particle Detector Development and Performance
- Adaptive optics and wavefront sensing
- Particle accelerators and beam dynamics
- Pulsars and Gravitational Waves Research
- Mechanics and Biomechanics Studies
University of Crete
2015-2024
Foundation for Research and Technology Hellas
2016-2024
Irkutsk National Research Technical University
2024
Campbell Collaboration
2023
St Petersburg University
2013-2022
MIREA - Russian Technological University
2020
Institute of Applied Astronomy
2010-2019
California Institute of Technology
2018
Max Planck Institute for Radio Astronomy
2018
Goddard Space Flight Center
2018
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,...
A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto hole, which heats the sufficiently to emit x-rays. We report polarimetric observation of XRB Cygnus X-1 using Imaging Polarimetry Explorer. The electric field position angle aligns with outflowing jet, indicating that jet launched inner emitting region. polarization degree (4.01+-0.20)% at 2 8 kiloelectronvolts, implying accretion disk viewed closer edge-on than orbit. observations reveal...
Context. It has been demonstrated that at least 10% of the brightest blazars in fourth Fermi-LAT catalog γ -ray sources exhibit repeating patterns flares. These events may be associated with presence a non-uniform sheath surrounding fast jet spine some blazars. Theoretical models suggest such could facilitate neutrino production these structured jets. Aims. We aim to test marginal statistical evidence previously reported for connection between flares and high-energy are positionally...
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 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 present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during first two years Fermi Gamma-ray Space Telescope mission. While investigating previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that emission appears delayed with respect to gamma-ray about 10 days. X-ray reveal pair `isolated' flares separated ~90 days, only weak counterparts. The spectral structure measured...
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 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...
Since the launch of Fermi satellite, BL Lacertae has been moderately active at gamma-rays and optical frequencies until May 2011, when source started a series strong flares. The exceptional sampling achieved by GLAST-AGILE Support Program (GASP) Whole Earth Blazar Telescope (WEBT) in collaboration with Steward Observatory allows us to perform detailed comparison daily gamma-ray observations Fermi. Discrete correlation analysis between emission reveals time lag 0 +- 1 d, which suggests...
We present first results on polarization swings in optical emission of blazars obtained by RoboPol, a monitoring program an unbiased sample gamma-ray bright specially designed for effective detection such events. A possible connection swing events with periods high activity gamma rays is investigated using the dataset during season operation. It was found that brightest flares tend to be located closer time rotation events, which may indication two separate mechanisms responsible rotations....
We present average R-band optopolarimetric data, as well variability parameters, from the first and second RoboPol observing season. investigate whether gamma-ray-loud gamma-ray-quiet blazars exhibit systematic differences in their optical polarization properties. find that have a systematically higher fraction (0.092) than (0.031), with hypothesis of two samples being drawn same distribution fractions rejected at 3σ level. not found any evidence this discrepancy is related to redshift...
Abstract We study the possibility of using LiteBIRD satellite B -mode survey to constrain models inflation producing specific features in CMB angular power spectra. explore a particular model example, i.e. spectator axion-SU(2) gauge field inflation. This can source parity-violating gravitational waves from amplification fluctuations driven by pseudoscalar “axionlike” field, rolling for few e-folds during The sourced exceed vacuum contribution at reionization bump scales about an order...
Abstract Observations of linear polarization in the 2–8 keV energy range with Imaging X-ray Polarimetry Explorer (IXPE) explore magnetic field geometry and dynamics regions generating nonthermal radiation relativistic jets blazars. These jets, particularly blazars whose spectral distribution peaks at energies, emit X-rays via synchrotron from high-energy particles within jet. IXPE observations X-ray-selected BL Lac–type blazar 1ES 1959+650 on 2022 May 3–4 showed a significant degree Π x =...
Abstract We estimate the efficiency of mitigating lensing B -mode polarization, so-called delensing, for LiteBIRD experiment with multiple external data sets lensing-mass tracers. The current best bound on tensor-to-scalar ratio, r , is limited by rather than Galactic foregrounds. Delensing will be a critical step to improve sensitivity as measurements become more and lensing. In this paper, we extend analysis recent forecast paper include mass tracers, i.e., CMB maps from CMB-S4-like...
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 present measurements of rotations the optical polarization blazars during second year operation RoboPol, a monitoring programme an unbiased sample gamma-ray bright specially designed for effective detection such events, and we analyse large set rotation events discovered in two years observation. investigate patterns variability parameters total flux density compare them to behaviour non-rotating state. have searched possible correlations between average polarization-plane polarization,...
We use results of our 3 yr polarimetric monitoring programme to investigate the previously suggested connection between rotations polarization plane in optical emission blazars and their gamma-ray flares GeV band. The homogeneous set 40 rotation events 24 sources detected by RoboPol is analysed together with data provided Fermi-LAT. confirm that are indeed related closest time lags these consistent zero. Amplitudes anticorrelated amplitudes flares. This presumably caused higher relativistic...
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.
We studied the radio emission from four radio-loud and gamma-ray-loud narrow-line Seyfert 1 galaxies. The goal was to investigate whether a relativistic jet is operating at source, quantify its characteristics. relied on most systematic monitoring of such system in cm mm bands which conducted with Effelsberg 100 m IRAM 30 telescopes covers longest time-baselines frequencies date. extract variability parameters compute brightness temperatures Doppler factors. powers were computed light curves...
Context. We investigate the optical polarization properties of high-energy BL Lac objects using data from RoboPol blazar monitoring program and Nordic Optical Telescope.
We present the first Bayesian method for tomographic decomposition of plane-of-sky orientation magnetic field with use stellar polarimetry and distance. This standalone inversion presents an important step forward in reconstructing magnetized interstellar medium (ISM) three dimensions within dusty regions. develop a model which polarization signal from ISM is described by thin layers at various distances, working assumption should be satisfied small-angular circular apertures. Our modeling...
The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) monitored BL Lacertae in 2008-2009 at radio, near-IR, and optical frequencies. During this period, high-energy observations were performed by XMM-Newton, Swift, Fermi. We analyse these data with particular attention to calibration Swift UV data, apply a helical jet model interpret source broad-band variability. GASP-WEBT show an flare 2008 February-March, oscillations several tenths mag on few-day time scale...
We present multiwavelength observations of 3C 454.3 from April 2008 to March 2010. The radio optical data are mostly the GASP-WEBT, UV and X-ray Swift, gamma-ray AGILE Fermi satellites. improved calibration optical-UV UVOT OM instruments estimated Lyalpha flux disentangle contributions different components in this spectral region. reveal prominent variability above 8 GHz. In band, amplitude decreases with increasing frequency due a steadier radiation both broad line region an accretion disc....