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

In this work, I construct a LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 from the Sloan Digital Sky Survey Data Release 15 (SDSS DR15), which contains 184172 CMASS LRGs and 27158 eBOSS LRGs and examine the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors in this galaxy sample. I divide this LRG sample into subsamples with a redshift binning size of Δz = 0.01, and analyze the environmental

We have investigated the methanol CH3OH lines at frequencies of 19.967 GHz [21-30 E(vt = 0) transition] and 20.971 GHz [101-112 E+(vt = 1) transition] toward the massive region of active star formation G358.931-0.030 with the RT-22 (Simeiz) and RT-26 (HartRAO) radio telescopes. Two new flares have been detected. One of the flares (at 20.971 GHz) is extremely powerful in the frequency range 192-26 GHz

Possible models for the generation of electromagnetic (EM) radiation during the coalescence of neutron star–black hole binaries are considered. The mass of the remnant disk around the black hole during the coalescence of neutron stars and black holes is calculated by taking into account the equation of state for neutron stars and the rotation of the binary components before the coalescence. The parameters

The high-resolution Jet Propulsion Laboratory DE431 and DE432 planetary ephemeris are used to evaluate the instantaneous eccentricity functions of the orbits of the planets of the solar system from 13 000 BC to 17 000 AD at different time scales. Spectral analyses are performed to determine the frequencies and the amplitudes of the detected perturbations from 0.1-year to 10 000-year periods. Taken

The results of observations of the gravitational-wave (GW) event S190425z recorded by the LIGO/Virgo detectors with the anti-coincidence shield (ACS) of the SPI gamma-ray spectrometer onboard the INTEGRAL observatory are presented. With a high probability (>99%) it was associated with a neutron star (NS) merger in a close binary system. This is only the second event of such a type in the history of

Based on archival Hubble Space Telescope images, we have performed stellar photometry for 18 dwarf galaxies. Branches of young and old stars are seen on the constructed Hertzsprung–Russell diagrams. Using the photometry of red giants and applying the TRGB method, we have determined accurate distances for all 18 galaxies for the first time. The galaxies AGC 238890 and AGC 747826 have minimum (D = 5

Based on a sample of 7696 nonrecurrent and 566 recurrent sunspot groups, we have investigated the Gnevyshev–Waldmeier rule using the Catalogue of Solar Activity by R.S. Gnevysheva (1954–1978). The maximum recorded sunspot group lifetime is 160 days. The general Gnevyshev–Waldmeier rule for all lifetimes is Amax = (12.1 ± 0.70)LT (Amax is the maximum sunspot group area during the lifetime and LT is

For the low-amplitude Cepheid V532 Cyg we have constructed an O − C diagram spanning a time interval of 121 years. The O − C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, dP/dt = −0.248 (±0.067) s yr−1, which points to the second crossing of the instability

The influence of large-scale perturbations in a circumstellar disk on the linear polarization of UX Ori stars is considered. We show that the position angle of the intrinsic linear polarization of a star surrounded by a geometrically thin flared disk cannot change significantly after the passage through the photometric minimum due to perturbations in the disk. In contrast, perturbations in a disk puffed

A systematic search for cosmic gamma-ray bursts (GRBs) and other short hard X-ray events in the archival data from the IBIS/ISGRI telescope of the INTEGRAL observatory over 2003–2018 has been carried out. Seven previously unknown GRBs have been recorded in the telescope field of view; all of them have been localized with an accuracy ≤2 arcmin. These events were not revealed by the INTEGRAL burst alert

Stellar evolution calculations were performed for population I stars with masses on the main sequence 1 M⊙ ≤ M0 ≤ 1.5 M⊙ up to the stage of a cooling white dwarf. The final helium flash LTP is shown to occur in post-AGB stars with initial masses 1.3 M⊙ ≤ M0 ≤ 1.32 M⊙ for the overshooting parameter f = 0.016. In the case of more effective overshooting (f = 0.018) the final helium flash occurs at initial

The mass distribution of transiting exoplanets has been corrected for observational selection effects: the probability of a mass determination (for planets detected by the Kepler Space Telescope) and the probability of a transiting configuration. The corrected mass distribution of exoplanets can be fitted by a power law with an exponent of \( - 2_{ - 0.16}^{ + 0.1}:\;{\textstyle{{dN} \over {dm}}} \propto

We have produced a sample of 58 edge-on spiral galaxies at redshifts z ~ 1 selected in the Hubble Ultra Deep Field. For all galaxies we have analyzed the 2D brightness distributions in the V606 and i775 filters and measured the radial (hr) and vertical (hz) exponential scale lengths of the brightness distribution. We have obtained evidence that the relative thickness of the disks of distant galaxies

We have studied the kinematic properties of the candidates for hot subdwarfs (HSDs) selected by Geier et al. from theGaiaDR2 catalogue. We have used a total of 12 515 stars with relative trigonometric parallax errors less than 30%. The HSDs are shown to have different kinematics, depending on their positions on the celestial sphere. For example, the sample of low-latitude (|b| < 20°) HSDs rotates around

For the low-amplitude Cepheid BY Cas we have constructed an O − C diagram spanning a time interval 123 years. The O − C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary increase in the period, dP/dt = +0.985 (±0.091) s yr−1, which points to the third crossing of the instability strip

We present the results of our new photometric observations of the chromospherically active star FR Cnc performed with a robotic telescope at the Zvenigorod Observatory of INASAN in March 2019. The observations were carried out from March 2 to 13, 2019, in the period of time that coincided most closely in time interval with the observations of this star with the Astrosat space telescope. A total of

Previously we have reported the detection of a sequence of three particle arrival events at energies above 1019 eV during one day and from a small sky region by two extensive air shower (EAS) arrays. We have shown that the probability of a chance coincidence of the three events is very low and suggested the arrival of a short-lived particle beam at the Earth. Here we refine the energies of the recorded

The radii of the inner and outer boundaries of the circumbinary habitable zone (CBHZ) and the radii of the circumbinary chaotic zone (CBCZ) have been calculated for close binary stars in the solar neighborhood with sufficient catalogue data. A subclass of binaries for which the CBCZ boundary is within the CBHZ boundaries (the CBCZ radius is larger than the inner CBHZ radius, but smaller than the outer

On July 12, 2014, an unusual light structure was observed in the NOAA 12109 sunspot umbra at the Horizontal Solar Telescope of the Sayan Observatory. It differed from traditional light bridges in that it was entirely within the umbra without any apparent connection with the penumbra or the photosphere. The observed light structure more closely resembles a light “island” in outward appearance. A scan

We compare the spatial stellar color variations with our three-dimensional analytical model of the spatial dust distribution to refine the properties of the dust layer in Galactic solar neighborhoods. We use a complete sample of 93 992 clump giants with a small admixture of branch giants from the Gaia DR2 catalogue in a spatial cylinder with a radius of 700 pc around the Sun extending to |Z| = 1800

Based on VLBA observations (NRAO archive) at λ = 2 cm, we have constructed radio maps of the Seyfert galaxy NGC 1275 with a resolution of 25 µas, the epochs of 1995–2015, and at λ = 7 mm (Boston University archive), the epochs of 2000–2015, with a resolution of 20 µas. We have identified a ring structure with a diameter ϕ ≈ 2 mas (1 pc) inclined at 60° to the plane of the sky that includes three centers