arXiv subjects

Marina S. Butuzova

Publications and source records attributed to Marina S. Butuzova.

9 recordsLinked to original sources

arXiv2026

Correlation of gamma-ray and optical variability of BL~Lacertae during the period of high blazar activity

Investigating the correlation of flux variability in blazars across multiple spectral bands provides a key tool for constraining emission mechanisms and jet physical parameters. We study the gamma-ray and optical variability correlation of BL Lacertae on timescales of about 1 day during September 2022, when the source was within the TESS field of view, and over a longer period (April 2022 - September 2023) encompassing its gamma-ray flare, which finishes the series of flares during the high-activity phase. Our analysis confirms the Synchrotron Self-Compton mechanism as the origin of the gamma-ray emission, characterized by a zero time lag. For the longer interval, the Discrete Correlation Function (DCF) reveals a second statistically significant peak at the time lag of about 12 days. We demonstrate that this peak arises due to the presence of an additional flare in one of the bands, which accompanies a gamma-ray and optical flares correlated at zero time lag. We interpret the orphan flare origin in terms of the propagation of an injected blob of high-energy electrons along a jet with a decaying magnetic field, accounting for electron radiative cooling.

astro-ph.HE↗

arXiv2023

Configuration of the global magnetic field in AGN parsec-scale jets

The magnetic field plays a significant role in the phenomenon of highly collimated jets of active galactic nuclei (AGN). Relativistic effects prevent the direct reconstruction of the magnetic field direction as transverse to electric vectors on radio maps. We determined the topology of the B-field by modeling the transverse distributions of the total and linearly polarized intensity, polarization degree, and deviation of the polarization direction from the local jet axis and by further comparison with observational data. We consider (i) a helical field with a different twist angle; (ii) a toroidal field on the jet axis surrounded by a sheath with a longitudinal field. In the latter scenario, we consider different sheath thickness relative to the spine. We assumed the sheath velocity is equal to or less than that of the spine. The relativistic effects have been considered for a general case, under which the axis and velocity vector of the jet and radial directions do not coincide. Our simulations reproduce the main features of the observed transverse profiles of polarization characteristics in parsec-scale AGN jets. The model transverse distribution shapes of the polarization properties are found to be strongly influenced by kinematic and geometric parameters of an outflow. We demonstrated it for three AGNs having different but typical polarization patterns revealed on radio maps. For each of these objects, we identified the model parameters, which provide a qualitative correspondence of theoretical profiles with those obtained from observations, indicating that the B-field is strongly ordered on parsec scales.

astro-ph.HE↗

arXiv2022

The observed polarization direction depending on geometrical and kinematic parameters of relativistic jets

The study of the polarization direction is crucial in the issue of restoring the spatial structure of the magnetic field in the active galaxy parsec-scale jets. But, due to relativistic effects, the magnetic field projected onto the celestial sphere in the source reference frame cannot be assumed to be orthogonal to the observed direction of the electric vector in the wave. Moreover, the local axis of the jet component may not coincide with its motion direction, which affects the observed polarization direction. In this article, we analyze the transverse to jet distributions of the electric vector in the wave, obtained as a result of modeling with different jet kinematic and geometrical parameters for a helical magnetic field with a different twist angle and for a toroidal magnetic field in the center, surrounded by a varying thickness sheath, penetrated by a poloidal field. We obtained: 1) the shape of the electric vector transverse distribution depends in a complex way on the angles of the jet axis and the velocity vector with the line of sight; 2) ambiguity in determining the twist direction of the helical magnetic field under using only the distributions of the electric vector in the wave; 3) both considered magnetic field topologies can reproduce both the ``spine-sheath'' polarization structure and individual bright details with the longitudinal to the jet axis polarization direction.

astro-ph.HE↗

arXiv2022

Long-term multiband optical variability of S5 0716+714 blazar

Multiband optical photometry data of blazar S5 0716+714 obtained from 2002 to 2019 reveal stable color index change with flux variability. We analyzed this trend under variability caused by the Doppler factor change in the presence of a curved photon energy spectrum. A break in the energy spectrum of emitting electrons, caused by radiative losses, or log-parabolic electron energy distribution, or the synchrotron self-absorption acting in a compact jet part forms such the photon spectrum. We explained the observed color index change with variability by geometric effects only under the assumption that the radiating region is the synchrotron self-absorbed core and the bright optically thin jet. In this framework, we estimated the magnetic field strength in the optically thick part of the radiating region. These values correspond to other independent estimates of the magnetic field near the black hole, further supporting our assumption.

astro-ph.HE↗

arXiv2021

Geometrical and Kinematic Parameters of the Jet of the Blazar S5 0716+71 in a Helical-Jet Model

Periodic variations of the position angle of the inner jet of the blazar S5 0716+71 suggest a helical structure for the jet. The geometrical parameters of a model helical jet are determined. It is shown that, when the trajectories of the jet components are non-ballistic, the angle between their velocity vectors and the line of sight lies in a broader interval than is the case for ballistic motions of the components, in agreement with available estimates. The contradictory results for the apparent speeds of components in the inner and outer jet at epochs 2004 and 2008-2010 can be explained in such a model. The ratio of the apparent speeds in the inner and outer jet is used to derive a lower limit for the true speed of the components ($β>0.999$) and to determine the pitch angle of the helical jet ($p=5.5^\circ$). The derived parameters can give rise to the conditions required to observe high speeds (right to 37$c$) for individual jet components.

astro-ph.GA↗

arXiv2021

Periods of the Long-Term Variability of the Blazar 0716+714 and Their Inter-Correlations in a Helical Jet Model

Various quasi-periods for the long-term variability of the radio emission, optical emission, and structural position angle of the inner part of the parsec-scale jet in the blazar 0716+714 have been detected. The relationships between these quasi-periods are interpreted assuming that the variability arises due to a helical structure of the jet, which is preserved from regions near the jet base to at least 1 milliarcsecond from the core observed in radio interferometric observations. The radiating jet components should display radial motions with Lorentz factors of $\approx3$, and decelerate with distance from the jet base. The best agreement with the data is given in the case of non-radial motions of these components with a constant physical speed. It is also shown that the helical shape of the jet strongly influences correlations both between fluxes observed in different spectral ranges and between the flux and position angle of the inner part of the parsec-scale jet.

astro-ph.HE↗

arXiv2021

The blazar OJ 287 jet from parsec- to kiloparsec-scales

The curved shape of the kiloparsec-scale jet of the blazar OJ 287 is analyzed in the framework of the precession of the central engine, on the existence on which a large number of studies over the past decades are based. The data necessary for the analysis of the kiloparsec-scale jet velocity and angle with the line of sight are obtained based on two competing assumptions about the X-ray emission mechanism of the OJ 287 jet. Namely, there were both the inverse Compton scattering of the microwave background under the assumption of relativistic kiloparsec-scale jet and the inverse Compton scattering of the central source radiation. For the latter one, we showed that the expected flux from the kiloparsec-scale jet in the gamma range does not exceed the limit set for it according to Fermi-LAT data. We found that only the period of the kiloparsec-scale jet helix, estimated in the framework of the inverse Compton scattering of the central source radiation, agrees with the precession period of the central engine, determined from the modulation of the peak values of 12-year optical flares.

astro-ph.HE↗

arXiv2021

A geometrical interpretation for the properties of multiband optical variability of the blazar S5 0716+714

We present the results of multiband observations of the blazar S5 0716+714 intra-night variability performed during 23 nights in the period from 04.2014 through 04.2015. The bluer-when-brighter trend is detected in both intra- and inter-night data. We assume that the jet component crossing the region where the medium becomes transparent to the optical radiation forms almost all optical emission of S5 0716+714. Deviations of some parts of the component from the general trajectory of the component can cause the Doppler factor of these parts to increase. Various maximum Doppler factors achieved by these parts of the component and different volumes occupied by them with the concave synchrotron self-absorption spectrum result in both the observed various color index behavior in variability and explain the absence of dependence of the bluer-when-brighter behavior on the object magnitude. We estimated spectral maximum frequency $ν_\text{m}\approx\left( 0.6-1.7\right)\cdot10^{14}$ Hz from intra- and inter-night data. Assuming that the size of emitting region is comparable with the gravitational radius of a black hole with a mass of $5\cdot10^8$ solar masses, the magnetic field obtained from synchrotron self-absorption is $B\sim10^2-10^4$ G, which corresponds to the values of other independent estimations. The obtained values of $ν_\text{m}$ and $B$ confirm our assumption about the nature of the blazar S5 0716+714 region radiating in the optical range.

astro-ph.GA↗

arXiv2019

Inverse Compton Scattering of the Central Source Photons as an X-ray Emission Mechanism on Kiloparsec Scales in PKS 1127-145

The beamed inverse Compton/cosmic microwave background model has generally been used for the interpretation of X-ray radiation from kiloparsec-scale jets of the core-dominated quasars. Recent \textit{Fermi}-LAT and \textit{HST} observations have brought this model into question. We examine the assumption that X-rays from the kiloparsec-scale jet of the quasar PKS~1127$-$145 are produced by inverse Compton scattering of the central source emission. In this context, we show that both similarity and distinction between the observed radio and X-ray spectral indices for some of the jet knots can be explained under a single power-law electron energy distribution. We derive that the viewing angle of the kiloparsec-scale jet is about $35^\circ$ and the jet has a moderate relativistic speed of $\approx 0.8c$. The predicted gamma-ray flux of the jet is found to be a few orders of magnitude lower than the minimum flux level measured by \textit{Fermi}-LAT, further supporting our scenario.

astro-ph.HE↗