Abstract The apparent motion parameter (AMP) method is designed to determine the orbits of wide pairs of double stars with orbital periods of hundreds and thousands of years. This is a dynamical method using all that is known about the star at one moment to reconstruct its complete orbit within the two-body problem. The Gaia DR2 catalog contains all of the data for epoch 2015.5 that are needed to use

Abstract The nucleosynthesis of heavy elements in the scenario for the evolution of a close binary of neutron stars differing greatly in mass is considered. In contrast to the scenario for the merger of two neutron stars of comparable masses considered repeatedly in the literature, the evolution of such a binary at the final stage consists in a rapid mass transfer to the more massive star and an explosive

Abstract Based on SDSS data, we consider the fraction of active galactic nuclei among polar-ring galaxies. We have found evidence for an excess of Seyfert galaxies and LINERS among polar-ring galaxies compared to ordinary objects. The observed nuclear activity of polar-ring galaxies may be associated with the accretion of gas from the region of the polar structures onto the central galaxies.

Abstract The technique of spherical harmonics, both scalar and vector ones, has long been applied to analyze the astronomical data on a sphere, for example, in the representation of systematic errors, in stellar kinematics. Up to now, spherical harmonics have been used exclusively in heliocentric coordinate systems: the equatorial or Galactic one. To study the kinematics of the entire Galaxy (and not

Abstract Evidence of wind variability and velocity stratification in the extended atmosphere has been found in the spectra of the supergiant V340 Ser (\({=}\)IRAS 17279\(-\)1119) taken at the 6-m BTA telescope with a resolution \(R\geq 60\,000\). The H\(\alpha\) line has a P Cyg profile whose absorption component (\(V_{\odot}={+}34\) km s\({}^{-1}\)) is formed in the upper layers of the expanding atmosphere

Abstract On the basis of consistent stellar evolution and nonlinear stellar pulsation calculations, the Cepheid V1033 Cyg is shown to be the post-main sequence star at the first crossing of the instability strip during the gravitational contraction of the helium core. The observed light variability of V1033 Cyg is due to the radial oscillations in the fundamental mode. The best agreement (within one

Abstract The formation of the rubidium resonance lines is considered by taking into account the effects of departures from local thermodynamic equilibrium (LTE). A rubidium model atom has been constructed using 29 Rb I levels and the Rb II ground level. Non-LTE calculations have been performed for a grid of model atmospheres with \(T_{\textrm{eff}}\) from 3500 to 6500 K, \(\log g\) from 1.0 to 5.0

Abstract The laboratory simulations of jets from young stars that have been carried out for many years at plasma focus facilities allow the internal structure of the active regions emerging during the interaction of the jet with the surrounding plasma to be studied in detail. We have found a new wide class of solutions for the equations of ideal magnetohydrodynamics describing the closed axisymmetric

Abstract Based on observations with the new transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the types and found the redshifts for six new X-ray sources (four quasars and two galaxy clusters) detected by the SRG space observatory during the Lockman Hole observations at the eROSITA performance verification phase. We show

Abstract The collisional pumping of OH masers in non-dissociative C-type shocks near supernova remnants is considered. The emergence of maser emission in OH lines is investigated for various shock parameters—the shock speed, the preshock gas density, the cosmic-ray ionization rate, and the magnetic field strength. The largest optical depth in the 1720 MHz line is reached at high gas ionization rates

Abstract Based on published data, we have produced a sample of 256 radio sources whose trigonometric parallaxes and proper motions were measured by VLBI. This sample contains Galactic masers associated with massive protostars and stars in active star-forming regions. It also includes young low-mass stars from the Gould Belt region whose radio observations were performed in continuum. Based on this

Abstract Based on moderate-resolution spectra in the range 4200–5200 Å, we have studied B and Be stars in the young open star cluster NGC 581. The temperatures of the program stars have been derived by the differential method with the choice of simple spectroscopic parameters for a number of lines and their comparison with the analogous parameters of a large sample of B stars for which accurate estimates

Abstract We present the results of the first year of searching for polar candidates within the 3BS (3-Band Survey) program using medium-band filters. Observational data for 84 selected objects from the catalog of cataclysmic variables of the CRTS DR1 sky survey were obtained while implementing the program. A dwarf nova during its outburst and a polar were detected. The available archival data are analyzed

Abstract We discuss the model for the evolution of an active region (AR) in which the graph constructed from the singular points of the magnetic field codes the AR magnetic patterns. The AR dynamic scenarios are mapped by the discrete structure of the network formed from the maxima, minima, and saddle points of the magnetic field. The AR dynamics leads to a rearrangement of the graph, graph dynamics

Abstract We have studied a sample of more than 25 000 young stars with proper motions and trigonometric parallaxes from the Gaia DR2 catalogue. The relative errors of their parallaxes do not exceed 10\(\%\). The selection of stars belonging to active star-forming regions was made by Marton et al. based on data from the Gaia DR2 catalogue by invoking infrared measurements from the WISE and Planck catalogues

Abstract We present the first results of Mars neutron sounding by FREND instrument onboard ESA’s Trace Gas Orbiter data analysis. Neutron flux mapping is performed with high spatial resolution, which allows to match epithermal neutron flux variation with relief’s geomorphological structures. Local regions with suppressed neutron flux indicate the presence of considerable amount of hydrogen atoms in

Abstract We present the results of our numerical simulations of the general circulation in the atmosphere of a hypothetical super-Earth within a model based on the solution of the complete system of hydrodynamic equations. The MIPT/PGI GCM model used for our computations has already been successfully adopted to describe the general circulation of the atmosphere of Venus. The model features high resolution

Abstract We have solved the problem of the acceleration of ions (protons) incident on the front of a nonlinear whistler for which the structure of its electromagnetic fields is assumed to be known and defined by the relations derived by us previously. We have established the dependence of the energy to which the protons are accelerated on the angle between the whistler propagation direction and the

Abstract We propose a method of analyzing the absorption spectra of quasars that allows the physical parameters of absorbing clouds, absorbers, to be roughly estimated: their masses, sizes, and mean densities. An analysis of three representative catalogs of the Lyman-alpha (\(Ly_{\alpha}\)) forest and metal absorption line systems confirms that these observations refer to two types of objects with

Abstract We consider the evolution of the abundance of singly and doubly deuterated isotopologues of water and methanol in a typical protostellar cloud. The main processes determining their abundance in various regions of the cloud have been revealed. We show that the abundances of the deuterated isotopologues can exceed the abundance of the main molecules in a number of cases.

Abstract The reduction of all the available photometry for the Cepheid EV Aql has allowed its \(O-C\) diagram spanning a time interval of 130 years to be constructed. This has made it possible to calculate the rate of evolutionary decrease in the period, \(dP/dt=-33.2({\pm}{6.9})\) s yr\({}^{-1}\), in agreement with the results of model calculations for the second crossing of the instability strip

Abstract We consider the dynamical evolution of planetary systems whose structure is nearly circular and coplanar. The analysis is performed by the Hori–Deprit averaging method within the theory of the first order in planetary masses. A convenient set of canonical elements and a rarely employed variety of astrocentric coordinates are used to derive the equations of motion. Owing to the use of the chosen

Abstract I explore the origin of an asymmetry of the H\(\alpha\) emission from a circumstellar (CS) shell around type IIP supernova SN 2013fs in the spectrum taken 10.3 h after the shock breakout. A spherical model of the H\(\alpha\) emission from the CS shell that takes into account a preshock gas acceleration by a supernova radiation permits us to successfully reproduce the H\(\alpha\) profile. Principal

Abstract We present the results of our determination of the fundamental atmospheric parameters for the magnetic chemically peculiar Ap stars HD 110066 (AX CVn) and HD 153882 (V451 Her). The determination of the atmospheric parameters (\(T_{\textrm{eff}}\), \(\textrm{log}{g}\), \(R/R_{\odot}\), and \(L/L_{\odot}\)) is based on a self-consistent analysis of high-resolution spectra (ESPaDOnS with \(R=65\

Abstract The sensitivity of future far-infrared telescopes, such as Millimetron, will be limited by the confusion noise produced by distant galaxies. We have constructed a model of the cosmic infrared background whose main goal is to investigate the confusion noise parameters. The model is based on the publicly accessible eGALICS simulation. For each galaxy from the simulation we construct a model

Abstract We present the results of our spectroscopic study of the lenticular galaxy NGC 4143—a peripheral member of the Ursa Major cluster. Using the observations at the 6-m SAO RAS telescope with the SCORPIO-2 instrument and the archival data of panoramic spectroscopy with the SAURON instrument at the WHT, we have detected an extended inclined gaseous disk in this lenticular galaxy with a spin approximately

Abstract The evolutionary calculations for population I stars with masses on the main sequence \(5M_{\odot}\leq M_{0}\leq 6.1M_{\odot}\) and initial fractional abundances of helium \(Y_{0}=0.28\) and heavier elements \(Z_{0}=0.02\) were carried out to the stage of central helium exhaustion. Selected core helium–burning models were used as initial conditions for solution of the equations of hydrodynamics

Abstract We consider the effect of a change in the rate of flux decline in the \(U\) band for type II-P supernovae (SNe IIP) as a function of metallicity \(Z\). Based on this effect, we propose a new method to determine the photometric redshift from the SN IIP light curve in the \(U\) band. Using the STELLA code, we have constructed model light curves in different bands for different redshifts \(z=0

AbstractThe Spectrum–Röntgen–Gamma (SRG) space observatory was launched from Baikonur on July 13, 2019, and is currently on a flight trajectory in the vicinity of the collinear Sun–Earth libration point L2. The planned service life of the observatory is 7 years and includes an all-sky survey and in-depth studies of individual objects in the X-ray range 0.3–15 keV. We consider the technical limitations

AbstractBased on long-term SWIFT, RXTE, and MAXI observations of the X-ray novae H 1743-322 (IGR J17464-3213) and GX 339-4, we have investigated the morphology and classified the light curves of their X-ray outbursts. In particular, we have confirmed the existence of two radically different types of outbursts, soft (S) and hard (H), in both sources and revealed their varieties, ultrabright (U) and

AbstractThe elliptic case of restricted four-body problem with variable mass of infinitesimal body is studied here. The three primary bodies which are placed at the vertices of an equilateral triangle and moving in the elliptical orbits around their common center of mass. Out of these primaries we have considered that one massive body is having radiating effect and other two bodies are oblate in shapes

AbstractWe have performed a theoretical calculation of the influence of radiative pumping on the populations of the rotational levels of the ground vibrational state for HD molecules under conditions of the cold phase of the interstellar medium. Two main excitation mechanisms have been taken into account in our analysis: (i) collisions with atoms and molecules of the interstellar medium and (ii) radiative

AbstractThe reduction of all the available photometry for the Cepheid ET Vul has allowed its \(O-C\) diagram spanning a time interval of 130 years to be constructed. This has made it possible to calculate for the first time the rate of evolutionary decrease in the period, \(dP/dt=-426.5(\pm{29.7})\) s yr\({}^{-1}\), in agreement with the results of model calculations for the second crossing of the

AbstractThe oscillations in thin magnetic flux tubes in the solar corona are considered. The surface and fundamental modes of oscillations are shown to be the main modes of fast and slow oscillations. The slow surface and fundamental modes are waveguide ones. The fast surface mode is a leaky one, while the fast fundamental mode is a waveguide one. The fundamental modes considered by us exist only in

AbstractWe consider 36 candidates for close (within 1 pc) encounters with the Solar system. These stars have been selected in accordance with the results of an analysis of their motion obtained by various authors. For most stars from this list the kinematic characteristics have been taken from the Gaia DR2 catalogue. The parameters of the encounters of these stars with the Solar system have been calculated

AbstractThe results of ultrahigh-time-resolution (\(\Delta T\sim 12\) s) observations of the B1 Iab supergiant \(\rho\) Leo with the 1.25-m telescope at the Crimean Astronomical Station of the SAI MSU are presented. Regular line profile variations with periods of 15–30 min have been revealed. Significant changes in the average line profiles on time intervals of 1–3 days have been detected. Evidence

AbstractDuring a deep extragalactic Lockman Hole sky survey with an area of 18.5 sq. deg, which was conducted when the SRG observatory was flying to the Lagrange point L2, the eROSITA telescope detected \({\sim}7000\) X-ray sources. These objects were then provisionally identified and classified using the publicly accessible data of optical and infrared sky surveys by the SRGz machine learning system

AbstractThe algorithm for the reduction of spectroscopic observations with the ASTRONIRCAM camera-spectrograph installed at the 2.5-m telescope of the Sternberg Astronomical Institute of the Moscow State University is described. The instrument allows spectra of astronomical objects with long (\(280^{\prime\prime}\)) and short (\(10^{\prime\prime}\)) slits to be taken in the wavelength range from 1

AbstractWe present the results of our analysis of the photospheric and chromospheric activity of the star DS Tuc (DS Tuc A, HD 222259A), which is a member of the Tucana–Horologium (Tuc–Hor) group with an age of 45 Myr. The star DS Tuc may be considered as the prototype of a young Sun, while its planetary system may be considered as the prototype of a young Solar system. Using data from the archive

AbstractThe motion of a spacecraft with a solar sail is considered within the restricted three-body problem of the Sun–Earth system. The equations of controlled orbital motion of the solar sail in the vicinity of the Sun–Earth collinear libration point \(L_{1}\) are investigated. Modified equations of the circular restricted three-body problem of the Sun–Earth system are used to describe the controlled

Abstract\(BVI_{c}g^{\prime}r^{\prime}i^{\prime}\) observations of the classical Cepheid V1467 Cyg have been obtained with the 60-cm telescope at the Caucasus Mountain Observatory of the SAI MSU. Invoking all of the available photometry has allowed an \(O-C\) diagram spanning a time interval of 107 years to be constructed. This has made it possible to calculate for the first time the rate of evolutionary

AbstractThe possibility of solving the problem of a discrepancy in the non-LTE abundances from Ti I and Ti II lines in metal-poor stars is investigated by applying accurate data to take into account the collisions with hydrogen atoms. For this purpose, we have calculated for the first time the rate coefficients for bound–bound transitions in inelastic collisions of titanium atoms and ions with hydrogen

AbstractWe present the results of a new epoch (2009–2019) of a long-term (50 years) photometric monitoring of the variable planetary nebula IC 4997 (QV Sge). The integral (star + nebula) \(UBV\) light curves display a continuing brightening of \(0\overset{m}{.}15\) in \(V\), a slight rise (\({<}0\overset{m}{.}1\)) in \(B\), and constancy in \(U\). The \(B-V\) color has got redder from \(0\overset{m}{

AbstractBased on an analysis of the dynamic spectra for solar flares in the meter wavelength range obtained with the ground-based Radio Solar Telescope Network, we consider the evolution of the parameters of harmonics in solar type II radio bursts. We have established that the relative separation between the bands behaves nonmonotonically and its value can change in a wide range, from 0.1 to 3. This

AbstractThe spatial and kinematic properties of a large sample of young T Tauri stars from the solar neighborhood 500 pc in radius have been studied. The following parameters of the position ellipsoid have been determined from the most probable members of the Gould Belt: its sizes are \(350\times 270\times 87\) pc and it is oriented at an angle of \(14^{\circ}\pm 1^{\circ}\) to the Galactic plane with

AbstractBy now the resonance lines of the isotope \({}^{7}\)Be have been detected in five novae. The known estimates of the relative abundance of this isotope from the equivalent widths of \({}^{7}\)Be II and Ca II lines lead to the conclusion that the \({}^{7}\)Be abundance is considerably higher than the predictions of thermonuclear burning models during a nova outburst. In an attempt to understand

AbstractWe present the results of spectroscopic redshift measurements for galaxy clusters from the catalogue compiled previously from Planck all-sky survey data in combination with Sloan Digital Sky Survey (SDSS) and WISE data in the optical and infrared ranges. Most of these clusters are massive objects that will also be detected in future all-sky surveys, such as the eROSITA all-sky X-ray survey

Abstract\(UBVJHKLM\) photometry for the carbon Mira star V CrB are presented. The infrared observations were carried out in the time interval 1989–2018, while the \(U\), \(B\), and \(V\) data were obtained in 2001–2014. The light and color curves are analyzed. The pulsation period of V CrB has been found to be \(355\overset{\textrm{d}}{.}2\) in the infrared \(JHKLM\) bands and \(352^{\textrm{d}}\)

AbstractAn example of simultaneous spectroscopic redshift measurements for a large number of galaxies in a cluster by multiobject spectroscopy with the medium- and low-resolution TFOSC spectrograph at the RussianTurkish 1.5-m telescope (RTT150) is presented. The redshifts of galaxies in the cluster \(0301.6+0156\) at \(z=0.17057\pm 0.0004\) detected previously by the SunyaevZeldovich signal in the

AbstractThis paper is a continuation of our work. The proper motions and radial velocities of stars from the Gaia DR2 with RV catalogue have been decomposed. We have confirmed that the Ogorodnikov-Milne model is consistent with the observational data and found the kinematic components that are not described by this model. The beyond-the-model harmonics have been partially identified with the nonlinear

AbstractFor accurate electron density diagnostics in the solar transition region, the principle of electron density diagnostics are discussed by lines from Si VIII ion for kappa and Maxwellian distributions By observed line ratio of the Si VIII 1440.50 to 1445.75 Å lines in quiet sun and active region, the electron density is discussed for any observed line ratio, and results are consistent with reported

AbstractOne of the possible bar formation mechanisms in the disks of galaxies was proposed by Lynden-Bell (1979). The presumed amplification of a weak seed oval stellar surface density perturbation in the central regions of the galaxy through the alignment of the major axes of precessing elliptical orbits underlies it. According to his qualitative reasoning, the orbits are aligned along the perturbation

AbstractWe present the results of our spectroscopic observations for the classical symbiotic star V1413 Aql in 20122017. In this period the system was in both active and rare (for it) quiescent states. In 2012 the optical spectrum was dominated by the radiation from the erupted hot component of spectral type F47 III. In 2017 the system passed to a quiescent state that lasted at least three months.

The possibility of obtaining dynamical estimates of the total masses in the two Trojan asteroid groups of Jupiter is investigated. The compact Greek (L4) and Trojan (L5) groups contain several tens of thousands of asteroids near the stable Lagrange points moving in a 1: 1 resonance with the orbital motion of Jupiter. The dynamical mass estimates$$\begin{array}{*{20}{c}} {{M_{L4}} = (8.63 \pm 0.51)

We show that Compton scattering by electrons of the hot intergalactic gas in galaxy clusters should lead to peculiar distortions of the cosmic background X-ray and soft gamma-ray radiation—an increase in its brightness at hv ≲ 60−100 keV and a drop at higher energies. The background distortions are proportional to the cluster gas surface density, in contrast to the intensity of the thermal gas radiation

The prospects for observations of gravitationally lensed extragalactic sources in the far-infrared and submillimeter ranges of the electromagnetic spectrum by the planned space observatories with active cooling of the telescope mirror to cryogenic temperatures are considered. The possibility of solving topical cosmological and astrophysical problems related to the observations of gravitationally lensed

We continue the study begun in Karasev et al. (2018) and present the results of our optical identifications of four hard X-ray sources from the INTEGRAL sky surveys. Having first improved the positions of these objects in the sky with the X-ray telescope (XRT) of the Swift observatory, we have identified their counterparts using optical and infrared sky survey data. Then, we have obtained optical spectra

The properties of low-mass neutron stars with rigid rotation are considered. The possible evolution paths of such stars in a close binary system with mass transfer are calculated. The properties of the gamma-ray burst GRB 170817A interpreted in terms of the stripping model, a natural ingredient of which is the explosion of a low-mass neutron star—a binary component, are briefly discussed.

The mechanisms of absorption formation in the cosmic microwave background (CMB) spectrum at the frequency of the 21-cm line of the transition between the ground-state hyperfine sublevels of the hydrogen atom are analyzed. We show that a strong nonlinearity at the compression stage of primordial matter density fluctuations can give rise to a significant (in depth) absorption even before the explosions

New versions of the ephemerides for the Galilean satellites of Jupiter (Io, Europa, Ganymede, and Callisto) constructed by numerically integrating the equations of motion of the satellites are presented. The satellite motionmodel takes into account the non-sphericity of Jupiter, the mutual perturbations of the satellites, and the perturbations from the Sun and major planets. The initial satellite motion