Том 72, № 2 (2017)

We study the variations of the properties of groups of galaxies with dynamical masses of 10¹³M_⊙<M₂₀₀<10¹⁴M_⊙, represented by two samples: one has redshifts of z < 0.027 and is located in the vicinity of the Coma cluster, the other has z > 0.027, and is located in the regions of the following superclusters of galaxies: Hercules, Leo, Bootes, Ursa Major, and Corona Borealis. Using the archived data of the SDSS and 2MASX catalogs, we determined the concentration of galaxies in the systems by measuring it as the inner density of the group within the distance of the fifth closest galaxy from the center brighter than M_K = −23_.^m 3. We also measured the magnitude gap between the first and the fourth brightest galaxies ΔM₁₄ located within one half of the selected radius R₂₀₀, the fraction of early-type galaxies, and the ratio of bright dwarf galaxies (Mr = [−18_.^m 5,−16_.^m 5]) to giant galaxies (M_r < −18_.^m 5) (DGR) within the radius R₂₀₀. The main aim of the investigation is to find among these characteristics the ones that reflect the evolution of groups of galaxies.We determined that the ratio of bright dwarf galaxies to early-type giant galaxies on the red sequence depends only on the x-ray luminosity: the DGR increases with luminosity. The fraction of early-type galaxies in the considered systems is equal, on average, to 0.65 ± 0.01, and varies significantly for galaxies with σ₂₀₀ < 300 kms⁻¹. Based on the luminosity of the brightest galaxy, the magnitude gap between the first and the fourth brightest galaxies in the groups, and on model computations of these parameters, we selected four fossil group candidates: AWM4, NGC0533, NGC0741, and NGC6098 (where the brightest galaxy is a double).We observe no increase in the number of faint galaxies (the α parameter of the Schechter function is less than 1) in our composite luminosity function (LF) for galaxy systems with z < 0.027 in the M_K = [−26m,−21_.^m 5] range, whereas earlier we obtained α > 1 for the LF of the Hercules and Leo superclusters of galaxies.

We applied the currently most comprehensive version of the statistical-parallax technique to derive the kinematical parameters of the maser sample with 136 sources. Our kinematic model comprises the overall rotation of the Galactic disk and the spiral density-wave effects, and the variation of radial velocity dispersion with Galactocentric distance. The best description of the observed velocity field is provided by the model with constant radial and vertical velocity dispersions, (σU0, σW0) ≈ (9.4 ± 0.9, 5.9 ± 0.8) kms⁻¹. The resulting Galactic rotation curve proved to be flat over the Galactocentric distance interval from 3 to 15 kpc and we find the local circular rotation velocity to be V₀ ≈ (235 − 238) ± 7 km s⁻¹. We determine the parameters of the four-armed spiral pattern (pitch angle i ≈ −10. ◦ 4 ± 0.3◦ and the phase of the Sun χ0 ≈ 125◦ ± 10◦). The amplitudes of radial and tangential spiral perturbations are about f_R ≈ −6.9 ± 1.4 km s⁻¹, f_Θ ≈ +2.8 ± 1.0 km s⁻¹. The kinematic data yield a solar Galactocentric distance of R₀ ≈ 8.24 ± 0.12 kpc. Based on rotation curve parameters and the asymmetric drift we infer the exponential disk scale H_D ≈ 2.7 ± 0.2 kpc assuming marginal stability of the intermediate-age disk, and also estimate the minimum local surface disk density, Σ(R₀) > 26 ± 3M_⊙ pc⁻².

We present a catalog of radio sources extending the RCR (RATAN Cold Refined) catalog to the right-ascension interval 2^h ≤ RA < 7^h. The list of objects was obtained in the process of a reprocessing of the observations of the “Cold” experiment conducted in 1980–1981 on RATAN-600 radio telescope at the declination of SS433, and the reduction of the 1987–1999 surveys of the same experiment.We report the right ascensions and integrated flux densities for 237 sources found at 7.6 cm (3.94 GHz) and their spectral exponents at 3.94 and 0.5 GHz. Twenty-nine sources of the list, which are mostly weaker than 30 mJy at 3.94 GHz, have available data only at two frequencies—1.4 and 3.94 Hz.We approximated the spectra of the sources using all catalogs available in the CATS and VizieR databases that meet the survey strip, and, in some cases, using the flux densities estimates from VLSSr,GLEAM, TGSS, and GB6 survey maps.We constructed the histograms of the spectral indices of the sources and verified the reliability of the identifications of sources found in the scans by comparing the coordinates and integrated flux densities with the corresponding parameters listed in the NVSS catalog. In the right ascension interval considered we found no objects at the 10–15 mJy level lacking in decimeter-wave catalogs.

Global magnetic fields of flare stars evolve very fast—at times of tens–hundreds of days. In our opinion, this is due to mutual addition of local magnetic fields generated by the differential rotation of these objects.With the example of two flare stars,OT Ser and YZCMi, we consider possiblemechanisms of generation and disspation of local and global magnetic fields and the mechanism of “magnetic deceleration” of these stars according to the scheme “differential rotation–generation of local magnetic fields–fluorescence of energy accumulated by local magnetic fields during flares.” We also estimated the rotation energy and global magnetic field for OT Ser and YZCMi. It is shown that even strong dissipation of the accumulated local magnetic energy in the flare on February 9, 2008 (UT 20:22:00) in YZCMi has not had any impact on the global magnetic field.

We investigate the question of the possible variable conditions in dwarf novae. The Balmer decrements are used as variability indicators due to their form being strongly dependent on the conditions in the radiating medium. It is shown that the decrements are usually anomalous and variable in time at minimum light, which indicates a variability of the conditions in the radiating medium. The spectrum changes significantly during the outburst state, the decrement becomes steep and has no anomalies. It appears that the outburst makes the emitting region more homogeneous and sparse. Another possible explanation is that the radiation is emitted by some other region, unseen at minimum light.

The results of studies of the optics of the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) by the Shack–Hartmann (SH) method are presented. Using a Shack–Hartmann wavefront sensor (SH WFS) we have adjusted the telescope optical system by means of shifts and tilts of the secondary mirror. The procedure has significantly reduced the aberrations that appeared during the long-term instrument operation. A new method to investigate the surface quality of the mirrors of the Zeiss-1000 being applied, characteristics close to the diffraction limit are achieved. In general, the entire opto-mechanical telescope system provides an image quality of about 0.5″ at 80%energy level.