This article is a brief survey of our previous work devoted to searching for candidate type FK Com giant stars and an analysis of data for yet another new candidate, KIC 7732964. Establishing that KIC 7732964 belongs to this group of stars requires further study of the evolutionary status of the star (dwarf, subdwarf, or giant). The star has fast rotation and high flare activity, which are more typical

Various solutions of the kinetic equation for the equilibrium of a gravitating sphere of uniform density with a quadratic gravitational potential and a linear dependence of gravitational force on radius are examined. New analytic solutions are obtained for a uniform sphere with a hollow spherical volume and central mass inside the sphere. Solutions are also obtained for an arbitrary number of spherical

Spectra taken with the 2.6-m telescope at the Byurakan Astrophysical Observatory (BAO) in the λλ4000-7250Å range for eight M giants from the KP2001 catalog confirm their oxygen-rich nature. The features of these spectra are examined. Several important physical parameters from the EDR3 Gaia data base are presented. The optical variability is studied using ASAS-SN monitoring data.

The study of the alignment of galaxy groups of the Tempel, Tago & Liivamägi (2012) catalog showed that detection of the alignment of the group galaxies with the group orientation depends on the position angle of the studied group. Alignment is detected in groups the position angle of which approximately coincides with the average position angle of the group galaxies that is about 90° for all groups

We study the modulation of galactic cosmic rays due to magnetic clouds observed during solar cycles 23 and 24 (1996-2018). We utilize solar wind plasma and field data together with cosmic ray intensity (CRI) data during the passage of magnetic clouds and associated structures. We apply superposed epoch analysis to analyze these data. We study the relative importance of magnetic clouds and their associated

The present paper deals with the Mannheim-Kazanas metric which is supposed to offer a reliable explanation on the observed galaxy rotation curves. The effective potential and the geodesic deviations are discussed. For a particular form of the metric, depending only on two parameters, the Gordon equation for massless bosons is satisfied by the Heun general functions. A special attention is given to

Based on new observations during 2015-2020 and published data, the unusual eruptive variables PV Cep and V350 Cep are examined. It is shown that PV Cep underwent a regular outburst followed by a drop in brightness that lasted overall from 2011 to 2019 and is still in a deep minimum. The outburst was accompanied by substantial changes in the intensity and profiles of a number of lines, including Hα

In this study, I investigate the environmental dependence of galaxy age in the CMASS sample of the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). It is found that galaxy age is very weakly correlated with the local environment. Considering the weak stellar mass-density relation of CMASS galaxies, it has been suggested that it is likely a combination of a strong age-stellar mass relation and

High precision data from the archive of the TESS space mission are used as the basis of a study of the photometric variability of two young analogs of the Sun with planetary systems: the stars HD 63433 (TOI 1726), a member of the Ursa Major moving group of stars with an age of 414 million years and TOI 451 (CD-38 1467) from the Pisces-Eridani star stream (Psc-Eri) with an age of 120 million years.

We used modified holographic Ricci dark energy to find anisotropic LRS Bianchi type I cosmological model in five-dimensions based on Lyra geometry. The exact solutions of the Einstein field equations were obtained by using hybrid expansion law (HEL). We have investigated the interacting and noninteracting dark energy and dark matter. It is found that at late times the equation of state parameter (EOS)

This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components. The purpose of this work has been to refine the orbital elements, estimate the masses, and search for possible manifestations of periodic components in deviations from the orbital motion. Observations on two instruments at

The chemical composition of the shell of a neutron star (SNS) at high temperatures and densities is discussed in this paper. A model for nucleosynthesis is proposed based on the approximation of nuclear statistical equilibrium (NSE). The dependence of the results of the nucleosynthesis on the parameters of the medium in a static approximation is studied. The results of this paper are qualitatively

The results of a photometric analysis of edge-on spiral galaxies in three blue fields of the Hubble Space Telescope (HDF-N, FDF-S, HUDF) are discussed. It is shown that galaxies at z ≈ 0.5 have lower values of the radial exponential scales hr of the stellar disks compared to nearby galaxies. The observed variation in the scales of the disks is consistent with a n hr ∝ (1 + z)–n law, where n ≈ 1. Indications

Studies of the magnetic fields of Herbig Ae/Be (HAeBe) stars can aid in understanding how the magnetic fields of AB stars of intermediate mass are created and evolve. It has been shown that the magnetic fields and magnetic fluxes of HAeBe stars before they emerge on the main sequence are significantly lower than for their successors, main sequence AB stars. In order to explain this mystery, the effect

We present the first photometric observations and light curve modelling of the discovered systems GSC 01870-00458 and USNO-A2.0-0975 04721840. Our modelling was carried out using a recent Windows interface version of Wilson and Devinney code based on model atmospheres provided by Kurucz. The accepted models revealed absolute and physical parameters that can be used to study the evolutionary states

The results of detailed studies of the galaxy with star-formation activity SBS 1539+597 based on panoramic spectroscopy are presented. This work was done as part of our project for the comprehensive study of ~500 galaxies in seven selected fields of the Second Byurakan Survey (SBS). The observations of SBS 1539+597 were made on the 6-m telescope at the Special Astrophysical Observatory of the Russian

Using known values of rotational and centrifugal distortion constants in conjunction with electric dipole moment of NH2CHO, we have calculated energies of rotational levels in the ground vibrational state, and the probabilities for radiative transitions between the levels. The radiative transition probabilities in conjunction with the scaled values of collisional rate coefficients are used in the Sobolev

The orbits of visual binary systems still attract the interest of many working groups in astronomy. These orbits are the most important and reliable sources of stellar masses. In the present paper, we computed the orbits and dynamical masses of some visual binaries using an independent code. We used the Kowalsky method to compute the geometrical elements, while the dynamical elements (the orbital period

This is a study of drift waves in the electron-positron plasma of the magnetosphere of a pulsar. It is shown that the nonlinear interaction of the drift waves with the plasma particles leads to the formation of small-scale structures. The cyclotron instability which develops in these structures may be the reason for the formation of the nano-outbursts discovered in the radio emission of a pulsar in

Cyanamide (NH2CN) has pyramidal equilibrium structure with two substates, denoted by 0+ and 0–. For each state of NH2CN, knowing rotational and centrifugal distortion constants in conjunction with electric dipole moment, energies for rotational levels and the probabilities for radiative transitions between the levels are calculated. The radiative transition probabilities in conjunction with scaled

In this study we continue spectral class determinations for large numbers of optically faint periodic variables taken from the Catalina Surveys Data Release 1 (CSDR1) and LINEAR data sets. Spectral classes and physical parameters are presented for 1184 periodic variables with periods P ≥ 10 days, taken from modern large sky area spectroscopic and photometric databases, including LAMOST (Large Sky Area

Non-singular Kruskal-like coordinates of some black holes space-times in f (R) gravity are presented in this research paper, and are also removed by establishing Kruskal-Szekeres coordinates for Non-extremal case. Carter-like coordinates can also be built for its extreme case.

The emission spectrum of dust undergoing substantial temperature fluctuations behind strong shocks (>100 km/s) is modeled. The model includes calculating the temperature distribution function of the dust particles owing to stochastic heating by electrons in the ambient plasma, as well as the features of the resulting spectral distribution of the emission from the dust. As the surrounding plasma cools

In this paper, we have studied Friedmann-Robertson-Walker space-time in the presence of domain walls in the framework of f(G) theory of gravitation. We propose the generalization of linearly varying deceleration parameter. It is observed that the universe is accelerating and expanding. The values of state finder parameters are close to ΛCDM model. Some physical parameters of the obtained models are

Solar activity of an explosive character during the 23rd and 24th cycles is analyzed. X-ray observations from the GOES-15 satellite during flares and observations during coronal mass ejections (CME) with the SOHO/LASCO coronagraph are used. The delay intervals between the onset of a flare and the onset of a Halo-type CME associated the same active region were analyzed. It is shown that the time interval

Results from a study of low resolution spectra and kinematics of the star V1117 Her located at a high galactic latitude b = +33°.8 are presented. It is shown that this star has A7 IV photospheric class, luminosity L ≈ 26 Lʘ, and spectral signs of accretion activity. This confirms its previous classification as a young Ae Herbig star with photometric UX Ori type variability. In addition, the parallax

The mass spectra of astronomical objects of various kinds are compared: cosmic dust, asteroids, planets, stars, star clusters, galaxies, and galactic clusters. The authors have previously noted a similarity in the (initial) mass functions for relatively massive objects (stars, galaxies, galactic clusters). In this paper the range of masses of astronomical objects is extended to the limit and covers

This paper is the second part of the author’s previous work. Its purpose is to illustrate the efficiency of using the previously introduced auxiliary functions known as linear images (LI) of the reflection-transmission function with simple examples of nonlinear problems for a one-dimensional purely scattering medium. First, an explicit analytic solution is obtained for the nonlinear “direct” problem

This is a theoretical study of changes in several characteristics of the spectra of early-type supergiants owing to scattering of continuum radiation. Thomson scattering on free electrons is treated as the scattering mechanism, although the approach used here is quite general. The reason for changes in the spectral class of a star with constant bolometric luminosity and surface temperature is elucidated

Results are presented from a study of the binary star ADS 7251 (STF 1321) based on a uniform series of observations on the 65-cm refractor at Pulkovo from 1962 through 2018. The errors in the yearly average positions ρ and θ are equal to 0′′.004 and 0°.02 for the photographic and 0.”003 and 0.°01 for the CCD observations. A new orbit is calculated from the found relative position and the exact parallax

Photometric studies of the SU UMa-type dwarf nova IRXS J161659.5+620014 have been made on the 2.6-m and 1.25-m telescopes at the Crimean Astrophysical Observatory during 2017 and 2018 in the quiescent state of the system, during normal outbursts, and during superoutbursts. It is found that the interval between adjacent normal outbursts was about 11 days during 2017. Observations in the quiescent state

An exact explicit barometric formula is derived for an ultrarelativistic degenerate Fermi-gas governed by the Chandrasekhar equation of state.

New observational data on the last two outbursts of the EXor star V1118 Ori are presented. The combined light curve of the last outburst is derived and fitted. The dates of the start of the outburst, its maximum, and end, as well as the maximum magnitude, and the rates of increase and decrease of the brightness were determined.

Parametrized Post-Newtonian (PPN) equations of motion for several S-stars nearest to the Galactic Center compact relativistic object SgrA* are considered. The effect of the orbital periods difference between Newtonian and Post-Newtonian cases is taken into account. The best fit PN orbit of S2 has a period which is 16 days longer than Newtonian one. The PPN parameters $\beta_\text{PPN}$ and $\gamma_\text{PPN}$

Results from spectral observations of known emission stars in the vicinity of Cyg OB7 are presented. 64 spectra of 9 emission stars were obtained over the period 2001-2007. The equivalent widths of the most characteristic lines for T-Tau stars were obtained in all these spectra. It is noted that all the spectral lines manifest strong variations. The spectra of these stars are in the spectral range

Published data indicate a substantial increase in the differential rotation parameter ∆Ω of stars hotter than 6700 K. By analyzing the shape of the light curves and the presence of a specific set of peaks in their power spectra, we have found that 47 of 57 objects with Teff greater than 7500 K that were studied can be identified as pulsating stars and only 10, as stars with brightness variation owing

We report the results of broadband observations of distant blazar PKS 0537-286 (z = 3.1) using data spanning more than ten years from the Fermi Large Area Telescope together with Swift UVOT/XRT archival data taken between 2005 and 2017. In the γ -ray band, the peak flux above 100 MeV, F$_{γ}$ = (6 23 ± 0 56) ∙ 10$^{-7}$ photon cm$^{-2}$ s$^{-1}$ observed on MJD 57874 within one week, corresponds to

We explore the distribution of position angles (PA) of galaxies in clusters. We selected for study the isolated clusters, since the distribution of the galaxy orientation in clusters with close neighbors could be altered by gravitational influence of the latter. We assume that galaxies are aligned, if their number at one $90^o$ position angle interval is more than twice higher than at the other $90^o$

We present the results of X-ray spectral analysis of the Seyfert type 2 galaxy Mrk 417 ( ɀ ≈ 0.0327 ) based on data from the NuSTAR (3-60 keV) and Swift/BAT (14-150 keV) space observatories. The spectrum from the NuSTAR observatory is well described by a basic power-law model with neutral absorption and an additional reflection component from a cold neutral medium (power-law index \( \Gamma ={1.63}_{-0

This is a detailed spectral classification of 96 active galaxies from the Véron-Cetty and Véron catalog (2010, Version 13, VCV-13) of active galaxies and quasars. These objects were identified as radio sources using standard radio catalogs. Those galaxies which had radio sources in at least 6 different radio bands and had been identified spectrally in the SDSS catalog were selected. The types of activity

Numerous indications that the magnetic field structures in magnetic stars do not change with age are cited. The stars rotate like a solid.

This is a study of spectral and photometric observations of the binary system with an X-ray component V725 Tauri=A0535+262. It consists of a giant star HDE 245770 of spectral class O9.7 and the pulsar A0535+26 with a pulsation period of ~103 s. Active stages of this object, accompanied by “giant” X-ray outbursts, have been observed repeatedly. The last events occurred during 2009-2011. Our studies

B3 1343 + 451 is a distant ( z = 2.534 ) and bright flat-spectrum radio quasar observed in the γ -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the γ -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 ± 0.83)·10-7 photon cm-2 s-1. The hardest photon index Γ =

The results of observations at high temporal resolution (∆T~4 min) of the B0.5V star e Per A on the 2-m telescope of the Terskol Observatory are reported. Regular components of variations in line profiles with periods 1.5-18 hours are recorded. Evidence of irregular variations in line profiles on time scales of minutes is detected. The nature of these variations is discussed.

The feasibility of detecting candidate slow-rotating magnetic Ap stars with periods from a few tens of days to several hundred years is considered. The question of the fraction of objects of this kind among all Ap stars is important from the standpoint of understanding the origin and evolution of magnetic stars. The search for such objects can be based on analysis of their photometric variability using

The physical conditions in the chromosphere of polar and equatorial coronal holes in the decay phase of the 24-th solar activity cycle are studied. Models of the chromosphere are constructed based on the intensities of the HeI 10830 Å and Hα lines and using a non-LTE program. The calculations showed that the temperature in equatorial coronal holes is similar to that of polar coronal holes. The temperature

The relationship between the magnetic fluxes and areas of coronal holes (CH) at mid and low latitudes |φ |< 60° and the mean magnetic field (MMF) of the sun over the period from January 19 through December 12, 2012, is studied using ultraviolet images and magnetograms obtained with the Solar Dynamics Observatory satellite. It is shown that the boundaries of the CH determined with the algorithms CHIMERA

Long-term automatic tracking of coronal bright points has made it possible to study their proper motions using data from the AIA 193 Å channel of SDO/AIA. Fits files for 95 visually long-lived bright points uniformly distributed in latitude have been chosen for processing. A specially developed program automatically fixes the heliographic coordinates of the centroid of the chosen coronal bright points

Solar active regions contain electric currents. Information on the distribution of currents is important for understanding the processes of energy release on the surface of the Sun and in the overlying layers. The paper presents an analysis of the probability density function (PDF) of the absolute value of the photospheric vertical electric current density ($|j_z|$) in 48 active regions before and

The hypothesis of two phases of charged particle acceleration in solar flares is well known, with subrelativistic electrons accelerated in the first phase and relativistic electrons and protons in the second. Both phases are distinguished in the solar proton events and their parent flares of December 26, 2001 (M7.1), November 2, 2003 (X8.3), and August 9, 2011 (X6.9), while in the interplanetary space

It is argued that, not only the blue (at the brightness maximum) but also the red (in the slow decay phase) components of the optical continuum of powerful flares on dMe stars are formed near the photosphere. The possible appearance of HeI lines in the relaxation zones for the plasma to a state of thermal equilibrium (as a result of a rise in electron temperature owing to elastic collisions of electrons

Data on solar hydrogen filaments obtained at the Abastumani Astrophysical Observatory during solar activity cycles 19-22 are used to study the characteristic periods of the solar differential rotation. In addition to the known 11-year period of solar activity, a quasi-biennial periodicity was revealed for the rotation rates of hydrogen filaments and a quasi-five-year periodicity was also found for

In the present paper, we are developing an analytical method for solving the time-dependent Kompaneets equation in its generalized form. The technique is generalizing the Dubinov and Kitayev method. In the particular case of a low photon number density, for the corresponding linear equation, the solutions are expressed in terms of Heun functions.

The fractal dimensions of cosmic microwave background (CMB) maps and other sources obtained by the “Planck” mission are investigated. It is shown that the choice of source distribution models used in data processing can significantly affect the fractal dimension of CMB.

A theoretical model of a cold and dense isolated solar prominence is presented. The thermodynamic parameters of a filament (gas pressure, density and temperature) are calculated from a specified magnetic field structure. The filament lies above the photospheric polarization separation line and its magnetic field falls off rapidly with distance from the axis, so that the total electric current along

Data from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) on the components of the magnetic field vector in the photosphere for 39 active regions (AR) of the 24th solar activity cycle are used to calculate the parameters of the electric current. The time variations in the electric current parameters in the AR over the time the region is within ±35° of the central

We present deep CCD photometry ( V ~ 21 mag) in BVR Johnson-Cousin filters supported with 2MASS JHKs data set for the open star cluster NGC 7790. The cluster’s parameters such as reddening, distance, metallicity and age etc… are derived using two color diagrams in optical and near-infrared bands. These parameters are E B-V = 0.512 ± 0.006, E V-R = 0.382 ± 0.005, E J-H = 0.337 ± 0.001 and E J-Ks = 0

In the present paper we use a complete set of CCD observations to model the light curves of the new W UMa systems, GSC 4835-1716 and USNO-A2.0_1275-10813091. The light curve modeling is performed by means of the W-D code where Kurucz (1993) model atmospheres are implemented. We treated the asymmetry of the observed curves using a spotted model. Physical parameters of the accepted model revealed that

This paper is a study of the spatial dynamics of microwave emission (data from the Nobeyama Radioheliograph) from two active regions NOAA 12673 and NOAA 11261 for several hours prior to powerful class M x-ray flares. The spatial distribution of the radio brightness and emission intensity in certain parts of the active region is found to be highly nonstationary. Data in the ultraviolet (AIA/SDO) are

Estimates of the integrated (SFR) and specific (sSFR) rates of star formation are given for 181 galaxies of later Sc, Scd, and Sd types seen almost face-on. Their SFRs were determined from FUV fluxes in the GALEX survey. The median values of the sSFR are: -10.66 dex for Sc, -10.44 dex for Scd, and -10.40 dex for Sd types in units of yr-1. The average value of the sSFR for these galaxies falls off smoothly