Determination of the Magnetic Field Strength and Geometry in the Accretion Disks of AGNs by Optical Spectropolarimetry

Based on the spectropolarimetric data of 33 Seyfert type 1 galaxies observed with the BTA-6m telescope of the Special Astrophysical Observatory, we estimated the magnetic field values at the event horizon of the supermassive black hole BH and the exponents of the power-law dependence s of the magnetic field on the radius. We used the model of optically thick geometrically thin Shakura–Sunyaev accretion disk. The average value of logBH[G] was found to be ∼4, which is in good agreement with the results obtained by other methods. The average value of s is s≈1.7, and its distribution maximum span is in the range od 1.85<s<2.0. This is a rather interesting result, since s=5/4 is usually adopted in calculations for Shakura–Sunyaev accretion disks. In addition, for two objects PG 1545+210 and 2MASX J06021107+2828382, the measured degree of polarization is greater than the maximum possible value at the angle between the line of sight and the axis of the accretion disk i=45°. It was concluded that for these objects the angle should be closer to i=60°.

Astronomical and Astrophysical Transactions, Vol. 32, No. 2

This issue of Astronomical and Astrophysical Transactions comprises the papers presented at the tenth annual conference on Modern Stellar Astronomy, held in Special Astrophysical Observatory of the Russian Academy of Sciences in October 2019. The “Modern Stellar Astronomy” conferences provide a forum for Russian scientists and scientists from the former Soviet Union concerned with stellar astronomy and related topics. The program consisted of invited talks, contributed oral talks, and poster papers. There were about 110 registered participants at the meeting. The program of the 2019 conference included 84 oral and 26 poster presentations. The key topics for the conference were Binary stars, Variable stars, Stellar clusters, Star formation, Exoplanets, Structure, kinematics and dynamics of the Milky Way Galaxy, Other galaxies. This volume comprises eleven of the papers that were presented at the conference.

3D structure of the H ii region Sh2-235 from tunable-filter optical observations

ABSTRACT We present observations of the H α, H β, [S ii] λλ6716, 6731 and [N ii] λ6583 emission lines in the galactic H ii region Sh2-235 with the Mapper of Narrow Galaxy Lines (MaNGaL), a tunable filter at the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We show that the H ii region is obscured by neutral material with AV ≈ 2−4 mag. The area with the highest AV is situated to the south-west from the ionizing star and coincides with a maximum detected electron density of ≳300 cm−3. The combination of these results with archive AKARI far-infrared data allows us to estimate the contribution of the front and rear walls to the total column density of neutral material in S235 and explain the 3D structure of the region. The H ii region consist of a denser, more compact portion deeply embedded in the neutral medium and the less dense and obscured gas. The front and rear walls of the H ii region are inhomogeneous, with the material in the rear wall having a higher column density. We find a two-sided photodissociation region in the dense clump S235 East 1, illuminated by a UV field with G0 = 50−70 and 200 Habing units in the western and eastern parts, respectively.

Atmospheric parameters at the 6-m Big Telescope Alt-azimuthal site

ABSTRACT In this paper, we introduce the results of the statistical analysis of atmospheric characteristics at the site of the Big Telescope Alt-azimuthal (BTA) of the Special Astrophysical Observatory (SAO) of the Russian Academy of Science (RAS). The BTA is the largest optical telescope in Eurasia and is located near Mt Pastukhova in the northern part of the Caucasus Mountains, at an altitude of 2070 m above sea level. The atmosphere of the Earth is a major challenge for observing and it limits the quality of astronomical images obtained by ground-based telescopes. The study of the atmosphere above astronomical observatories is important for the planning of observing time, for the optimization of instrument performance and for the development of adaptive optics systems. We discuss the results of a study of the meteorological conditions at the BTA site: total cloud cover, wind speed at the pressure level of 200 hPa, vertical motions, vertical profiles of the wind speed employing data from the ERA-Interim and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis data bases.

Spectroscopy and polarimetry of the gravitationally lensed quasar SDSS J1004+4112 with the 6m SAO RAS telescope

Context. We present new spectroscopic and polarimetric observations of the gravitational lens SDSS J1004+4112 taken with the 6 m telescope of the Special Astrophysical Observatory (Russia). Aims. In order to explain the variability that is observed only in the blue wing of the C IV emission line, corresponding to image A, we analyze the spectroscopy and polarimetry of the four images of the lensed system. Methods. Spectra of the four images were taken in 2007, 2008, and 2018, and polarization was measured in the period 2014–2017. Additionally, we modeled the microlensing effect in the polarized light, assuming that the source of polarization is the equatorial scattering in the inner part of the torus. Results. We find that a blue enhancement in the C IV line wings affects component A in all three epochs. We also find that the UV continuum of component D was amplified in the period 2007–2008, and that the red wings of CIII] and C IV appear brighter in D than in the other three components. We report significant changes in the polarization parameters of image D, which can be explained by microlensing. Our simulations of microlensing of an equatorial scattering region in the dusty torus can qualitatively explain the observed changes in the polarization degree and angle of image D. We do not detect significant variability in the polarization parameters of the other images (A, B, and C), although the averaged values of the polarization degree and angle are different for the different images. Conclusions. Microlensing of a broad line region model including a compact outflowing component can qualitatively explain the C IV blue wing enhancement (and variation) in component A. However, to confirmed this hypothesis, we need additional spectroscopic observation in future.

Spectra of comet C/2002 T7 (LINEAR)

We present the results of spectral observations of comet C/2002 T7 (LINEAR) carried out at the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory (Russia). The spectra were obtained within the 3500-7500 Å wavelength range on November 13, 14, and 21, 2003, before the perihelion passage, when heliocentric and geocentric distances of the comet were about 2.7 AU and 1.8 AU, respectively. Spectra do not show any emission features from the strongest cometary emissions of the CN, C2, and C3 molecules. The normalised spectral gradient of reflectivity is 2.8% per 1000 Å and 5.4% per 1000 Å for November 14 and 21, respectively. The Afρ parameter, which characterises the dust production rate in the comet, is on average about 800 cm. Comet C/2002 T7 (LINEAR) can be classified as belonging to the group of dusty comets