Том 74, № 2 (2019)

We review observational data about a sample of Local Volume objects containing about 1000 galaxies within 11 Mpc of the Milky Way. Dwarf galaxies with stellar masses M_∗/M_ʘ < 9 dexmake up 5/6 of the sample. Almost 40% of them have their distances measured with high precision using the Hubble Space Telescope. Currently, the LV is the most representative and least selection-affected sample of dwarf galaxies suitable for testing the standard ΛCDM paradigm at the shortest cosmological scales. We discuss the HII properties of dwarf galaxies in different environments and the star formation rates in these systems as determined from FUV- and Hα-survey data. We also pay certain attention to the baryonic Tully–Fisher relation for low-mass dwarf galaxies. We also point out that LV dwarfs are important “tracers” for determining the total masses of nearby groups and the nearest Virgo cluster.

We shortly summarize here the results of the second stage (1998–2018) of the detailed spectroscopy program of peculiar supergiants identified with galactic infrared sources, performed at the 6-m BTA telescope. The main aspect of the program is a search for the evolutionary variations in the chemical composition of stars, past the AGB stage and the TDU, as well as an analysis of spectral manifestations of kinematic processes in their extended, often unstable, atmospheres and in the envelopes. The most significant result is detection of the s-process element excesses in seven single post-AGB stars, which empirically confirms the theory of evolution of this type of stars. In three of these stars we for the first time discovered the ejection of the s-process heavy metals to the circumstellar envelopes. A lithium excess was found in the atmospheres of peculiar supergiants V2324 Cyg and V4334 Sgr. The results of investigation of the kinematics of atmospheres and shells will clarify the equilibrium of matter produced by stars in the AGB and post-AGB stages and delivered to the interstellar medium (ISM).

We report the results of long-term photometric observations of the magnetic white dwarfs WD 2047+372 and WD 0009+501, aimed to search for and study regular brightness variability in these stars. The data in the V band of the Johnson filter revealed signs of irregular variability in the convectively inactive white dwarf WD 2047+372 at times from hours to 1–3 days with characteristic amplitudes of about 0^m. 005. This variability can be due to both irregular proper pulsations of the star or even the debris disk and reasons of unidentified instrumental nature. We have not found the brightness variability of WD 2047+372 at the level of greater than 0^m. 005. As distinct from WD 2047+372, the convectively active magnetic white dwarf WD 0009+501 shows stable photometric variability associated with the proper rotation of the object and correlating with the variability of its magnetic properties. The variability amplitude is about 0^m. 01. Based on comparison of the observations of these two targets, we concluded on the photometric variability of magnetic dwarfs located in the thermal convection zone. We noticed the stable variability on long-term timescales (years, decades, and over).

We took a total of 635 B-, V-, and I_c-band CCD frames for the RRab Lyr type variable DVMon, which has a close bright visual companion with a separation of about 1.9′. Observations were made with the 76-cm telescope of the South African Astronomical Observatory (SAAO, South Africa) using SBIG CCD ST-10XME. For the first time, we obtained reliable separate PSF-photometry of both stars and determined their coordinates. We used all available data to construct the O — C diagram spanning a 110-year long time interval, which allowed us to reveal at least three sudden changes of the pulsation period around JD 2438000, 2453500, and 2456500. Our high resolution echelle spectra with the Southern African Large Telescope (SALT) showed that DV Mon belongs to type ab RR Lyrae variables of the Galactic thick disk.

Among the small bodies of the Solar System, at present, a group of bodies, called comets of the main belt, exhibiting dynamic and/or physical properties of both comets and asteroids is distinguished. One of the reasons for such manifestations may be collisions with other bodies. Asteroid (596) Sheila is one of the bodies belonging to the group of comets of the main belt. The study of its dust coma made it possible to estimate the relative velocity of the collision and the size of the body-impactor. In this paper, we searched for a possible impactor among known asteroids, comets, and meteor showers. A real of such a type body was not found, although it could be a fragment of a possible meteor shower of comet 232P/Hill. The performed simulation of close approaches of the asteroid (596) with fictitious bodies shows that the asteroid and the comet could be such an impactor. An estimate was made of the possible change in the velocity of the asteroid (596) as a result of a collision using its positional observations. 3456 observations from February 22, 1906 to the present have been used. However, the accuracy of determining the components of the change in velocity, about 1 mm s⁻¹, turned out to be insufficient for the confident determination of such a change.

The paper covers characteristics of big interferometers and reflecting radio telescopes intended for the studies of the solar atmosphere radiation. Solar radio interferometers (radioheliographs) have proven to be more cost-effective than single dish radio telescopes, since using the aperture synthesis allows for fast imaging of the Sun and its active regions with higher spatial resolution, thus, studying solar eruptive processes more efficiently. From the other hand, the studies of many fundamental aspects of the solar atmosphere physics requiring studies of low-contrast structures before and after flares gained no proper development. The efficiency of radio reflectors was enhanced in last decades mainly due to the development of matrix methods of reception, focal arrays, and also due to spectroscopic analysis in the wide wavelength range with high flux density sensitivity. Meanwhile, the diversity of issues related to the physics of the solar atmosphere and active processes requires an optimal combination of capabilities of various microwave interferometric and reflecting systems for joint studies of the Sun. In view of the started implementation of solar observation programs with a new instrument, ALMA, and obtaining newly observed data in the millimeter and submillimeter ranges, the areas of development of solar studies with the RATAN-600 radio telescope in the wide wavelength range are discussed.

The original paper can be found online at https://doi.org/10.1134/S1990341317030208. In the paper, the chemical symbols Na II should be understood as NII.