Yu. A. Kovalev
A5005359983- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Neutrino Physics Research
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
- Gyrotron and Vacuum Electronics Research
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- GNSS positioning and interference
- Superconducting and THz Device Technology
- Ionosphere and magnetosphere dynamics
- Cosmology and Gravitation Theories
- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Geophysics and Sensor Technology
- Geomagnetism and Paleomagnetism Studies
- Cardiovascular Health and Disease Prevention
- Cardiovascular Function and Risk Factors
- Internet of Things and Social Network Interactions
Russian Academy of Sciences
1980-2024
Astro Space Center
2011-2024
P.N. Lebedev Physical Institute of the Russian Academy of Sciences
2009-2024
Moscow Institute of Physics and Technology
2019-2023
Max Planck Institute for Radio Astronomy
2009-2023
Special Astrophysical Observatory
2022
Institute for Nuclear Research
2021
Ryazan State University
2019
Research Institute of Medical Problems of the North
2019
Joint Institute for Nuclear Research
2012
We have compared the radio emission from a sample of parsec-scale AGN jets as measured by VLBA at 15 GHz, with their associated gamma-ray properties that are reported in Fermi LAT 3-month bright source list. find our radio-selected photon flux correlates well quasi-simultaneously compact density. The LAT-detected complete generally higher densities, and cores brighter (i.e., brightness temperature) than non-detected objects. This suggests preferentially Doppler-boosting factors. In addition,...
Inverse Compton cooling limits the brightness temperature of radiating plasma to a maximum $10^{11.5}$ K. Relativistic boosting can increase its observed value, but apparent temperatures much in excess $10^{13}$ K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations quasar 3C273, made with space VLBI mission RadioAstron on baselines up 171,000 km, which directly reveal presence angular structure as small 26 $\mu$as (2.7 light...
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.
Abstract We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together contemporaneous ground VLBI 15, 43, 86 GHz. Ground-space fringes were obtained up to projected 3.9 Earth diameters session, record 15.1 snapshot sessions, allowing us image innermost jet an angular resolution ∼50 μ as, highest ever achieved for 287. Comparison...
We present observational results for extragalactic radio sources with milliarcsecond components, obtained the 600 meter ring telescope RATAN-600 from 1st to 22nd December, 1997. For each source, a six frequency broad band spectrum was by observing simultaneously an accuracy up minute at 1.4, 2.7, 3.9, 7.7, 13 and 31 cm. The observed list is selected Preston et al. (1985) VLBI survey contains all in declinations between -30deg +43deg correlated flux density exceeding 0.1 Jy sample includes...
Since September 2005, the Whipple 10m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five Northern Hemisphere blazars that have already detected at Observatory, Markarian 421, H1426+428, 501, 1ES 1959+650 and 2344+514, are monitored routinely each night they visible. We report on 421 observations taken from November 2005 to June 2006 in gamma-ray, X-ray, optical radio bands. During this time, was found be variable all wavelengths probed. Both variability...
We report on a multiwavelength campaign the radio-loud Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z=0.5846) performed in 2010 July-September and triggered by high-energy gamma-ray outburst observed Large Area Telescope (LAT) onboard Fermi Gamma-ray Space Telescope. The peak flux 0.1-100 GeV energy band exceeded, for first time this type of source, value 10^-6 ph cm^-2 s^-1, corresponding to an luminosity 10^48 erg s^-1. Although source was too close Sun position organize densely...
Active galactic nuclei (AGN) are some of the most luminous and extreme environments in Universe. The central engines AGN believed to be super-massive black-holes (SMBHs) fed by accretion discs threaded magnetic fields within a dense magneto-ionic medium. We report our findings from polarimetric very-long-baseline interferometry (VLBI) observations quasar NRAO,150 taken October 2022 using combined network Very Long Baseline Array (VLBA) Effelsberg 100-m Radio Telescope. These comprise first...
Observational information on high-energy astrophysical neutrinos is being continuously collected by the IceCube observatory. However, sources of are still unknown. In this study, we use radio very-long-baseline interferometry (VLBI) data for a complete VLBI-flux-density limited sample active galactic nuclei (AGN). We address problem origin with energies above 200 TeV in statistical manner. It found that AGN positionally associated events have typically stronger parsec-scale cores than rest...
The VSOP mission is a Japanese-led project to image radio sources with sub-milliarcsec resolution by correlating the signal from orbiting 8-m telescope, HALCA, global array of telescopes. Twenty-five percent scientific time this devoted survey 402 bright, small-diameter extra-galactic at 5 GHz. major goals Survey are statistical in nature: determine brightness temperature and approximate structure; provide source list for use future space VLBI missions; compare properties other data...
Recently we have shown that high-energy neutrinos above 200 TeV detected by IceCube are produced within several parsecs in the central regions of radio-bright blazars, is active galactic nuclei with jets pointing towards us. To independently test this result and extend analysis to a wider energy range, use public data for all neutrino energies from seven years observations. The point-source likelihood map analyzed against positions blazars statistically complete sample selected their compact...
Abstract Results are presented of long-term monitoring at the radio telescope RATAN–600 and a model interpretation instantaneous 1–22 GHz spectra six frequencies for sample 550 compact extragalactic sources. The sources selected from Preston et al. (1985) VLBI survey located in declination range −30° to +43°. Dependence index variability on frequency is analysed different subsamples. Factors flux density variations 1 15. A typical behaviour evolution during strong outbursts various objects...
The existence of high-energy astrophysical neutrinos has been unambiguously demonstrated, but their sources remain elusive. IceCube reported an association a 290-TeV neutrino with gamma-ray flare TXS 0506+056, active galactic nucleus compact radio jet pointing to us. Later, radio-bright blazars were shown be associated events high statistical significance. These associations remained unconfirmed the data independent experiments. Here we report on detection rare event estimated energy 224+-75...
Abstract We observed with the Very Long Baseline Array (VLBA) at 2.3 and 8.6 GHz a complete flux-density-limited sample of 482 radio sources decl. > +75° brighter than 200 mJy 1.4 drawn from NVSS catalog. A total 34% show parsec-scale emission above flux density detection limit 30 mJy; their accurate positions structure parameters are determined. Among all detected least shortest VLBA baselines, majority, or 72%, have steep single-dish spectrum. The fraction detectable is 95% among...
We present a statistical and model study of 1−22 GHz spectra 5-GHz interpolated data for 213 230 sources with declinations δ > −30°, selected survey observations the HALCA space radio telescope. The two subsamples were specially surveyed monitored in 1997-2000 as ground support VLBI framework VSOP Survey Programme. Every 1–22 spectrum was measured RATAN-600 telescope at six wavelengths 1.4, 2.7, 3.9, 7.7, 13, 31 cm over period few minutes (ten or more near pole). (25–30)% studied are...
ABSTRACT We conducted multi-epoch, multifrequency parsec-scale studies on the gigahertz-peaked spectrum quasar PKS 0858 − 279 with Very Long Baseline Array (VLBA). Our observations 2005 November 26 elucidated a weak core, characterized by an inverted spectrum, and distinctly bent jet that exhibited notable bright feature in its Stokes I emission. Through comprehensive analysis of polarization spectral data, we inferred formation shock wave within this feature, stemming from interactions...
ABSTRACT We present the results of our study cross-correlations between long-term multiband observations radio variability blazar 3C 279. More than a decade (2008–2022) data were collected at seven different frequencies ranging from 2 to 230 GHz. The light curves show variations in flux, with prominent flare features appearing first higher-frequency and later lower-frequency bands. This behaviour is quantified by cross-correlation analysis, which finds that emission bands lags Lag versus...
Baikal-GVD is a neutrino telescope currently under construction in Lake Baikal. GVD formed by multi-megaton subarrays (clusters). The design of allows one to search for astrophysical neutrinos already at early phases the array construction. We present here preliminary results high-energy with 2019-2020.
Pulse wave velocity (PWV) is a well-known indicator of arterial stiffness and marker the presence vascular lesions. Cardiovascular mortality in Russia has become highest world. The Japanese are enjoying long lives, caused by cardiovascular diseases thus far remained at lower levels than that Russia. In this study, we focused on brachial-ankle pulse (baPWV) obtained from normal human subjects as well Japan, compared their respective risks. We evaluated baPWV 337 138 Russian healthy subjects....