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Vol 34, No 6 (2018)
- Year: 2018
- Articles: 4
- URL: https://ogarev-online.ru/0884-5913/issue/view/11047
Solar Physics
Robust Method for Determination of Magnetic Field Strength in the Solar Photosphere
Abstract
The classical method for determining the magnetic field strength from the distance between the peaks of blue and red wings of the Stokes V profile of a magnetically sensitive spectral line is modified. To reduce the influence of noise and to more accurately measure the distance between these peaks, the observed Stokes V profile was approximated by a modified wavelet-function. The parameters of the best fitted approximation function were determined by multidimensional optimization. Following such an approach, the magnetic field strength can be found analytically using such an approximation. We investigate the modified method by means of calculations of the Fe I λ 1564.8 nm Stokes V and I profiles in a three-dimensional snapshot model atmosphere. Magneto-convection snapshot model with small-scale dynamo action performed by Rempel was used. It was found that the method proposed is less sensitive to noise and the shape of the observed V-signal of the line. This makes it possible to conclude that the approach of determining of the magnetic field strength from the observed splitting of the Fe I λ 1564.8 nm Stokes V profile is more reliable in comparison with the classical one.
277-289
Extragalactic Astronomy
Morphological Type and Color Indices of the SDSS DR9 Galaxies at 0.02 < z ≤ 0.06
Abstract
Abstract—The correlations of the color indices of central galaxies (Mr < –20.7) and their faint neighboring galaxies (Mr < –20.7) using the sample based on the SDSS DR9 (N = 60 561) have been studied. The galaxy sample was limited by the red shift 0.02 < z ≤ 0.06 and absolute magnitude –24m < Mr < –19.4m. The “Random Forest” method of machine learning was used to determine the morphological type of the galaxies. The statistically significant correlation was found only for the “central galaxies–nearest neighbor galaxy” pairs in which the distance between the components is less than 100 kpc and each of the components is an early type galaxy. The obtained results testify to the hierarchical scenario of the evolution of galaxies.
290-301
Obscured Active Nucleus of NGC 7172 as Seen by NuSTAR
Abstract
Abstract—The properties of X-ray emission of the active nucleus of the Seyfert 2 galaxy NGC 7172 detected by the NuSTAR space observatory in 2014 are analyzed. This source exhibits constant obscuration NH ≈ 8 × 1022 cm–2, which is similar to that determined by XMM-Newton, Suzaku, ASCA, and BeppoSAX in the past 30 years. Spectral analysis reveals the presence of a moderate reflection component with \(\left\langle R \right\rangle \) = 0.44 and a narrow FeKα line with EW = \(67_{{ - 14}}^{{ + 13}}\) eV. Numerical torus models confirm that the Seyfert nucleus of NGC 7172 is of a Compton-thin type and provide estimates of the torus inclination (Θi ≈ 61° and its opening angle (Θt ≈ 59°). The data of earlier observations reveal approximately order-of-magnitude variations of intrinsic luminosity Lintr(2–10 keV) and fourfold variations of equivalent width EW FeKα on a timescale of 12 years, which corresponds to distance d ≈ 3.7 pc. This behavior of Lintr(2–10 keV) is indicative of variability of the central source. The results of spectral analysis, the lag between variations of the intrinsic luminosity and EWFeKα, and the variation of intensity \({{I}_{{{\text{Fe}}{{K}_{\alpha }}}}}\) agree best with the scenario of production of the observed FeKα line in a distant gas-dust torus.
302-312
Instruments and Devices
Optimization of Video Camera Disposition for the Maximum Calculation Precision of Coordinates of Natural and Artificial Atmospheric Objects in Stereo Observations
Abstract
The problem of optimizing the disposition of a pair of video cameras to provide the maximum accuracy of the calculated radius and velocity vectors of natural and artificial objects in the atmosphere and near-earth space from double-station TV observations is considered. The effects of the video camera resolution and the accuracy of determining the positions of the observational sites on the accuracy of the calculated distance to the atmospheric object are investigated. A relation for calculating the relative determination error for the distance relative to the baseline is derived. Errors of components of the radius and velocity vectors are calculated using a Monte Carlo simulation of the direct problem. A 3D distribution is presented for the errors in calculating the coordinates of the object under observation. A demonstration is provided of the calculation accuracy for the absolute value of the body’s velocity and the error distribution for the velocity-vector direction on a sphere. The demonstration uses the calculated results for atmospheric kinematic parameters of meteors. A brief discussion is given of the possible fields to apply the results obtained: astronomy, geophysics, atmosphere physics, geodesy, aviation, and computer vision systems.
313-326