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  • Study of the Periodicities of the Solar Differential Rotation
    Astrophysics (IF 0.67) Pub Date : 2020-06-17
    D. Japaridze, G. Dumbadze, G. Ramishvili, B. Chargeishvili

    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

    更新日期:2020-06-17
  • New Solutions Generating Technique to Generalized Kompaneets Equation and the Corresponding Heun Functions
    Astrophysics (IF 0.67) Pub Date : 2020-06-15
    M. A. Dariescu, C. Dariescu

    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.

    更新日期:2020-06-15
  • Fractal Dimension of the Cosmic Microwave Background as a Test of "Planck" Spacecraft Data
    Astrophysics (IF 0.67) Pub Date : 2020-06-15
    P. A. Tarakanov, M. Y. Yezhkov, M. V. Kostina

    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.

    更新日期:2020-06-15
  • Fine Filament Structure of a Quiescent Solar Prominence
    Astrophysics (IF 0.67) Pub Date : 2020-06-11
    O. A. Korolkova, A. A. Solov’ev

    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

    更新日期:2020-06-11
  • Dynamics of Electric Current’s Parameters in Active Regions on the Sun and Their Relation to the Flare Index
    Astrophysics (IF 0.67) Pub Date : 2020-06-11
    Yu. A. Fursyak, V. I. Abramenko, A. S. Kutsenko

    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

    更新日期:2020-06-11
  • New Optical and Infrared Photometric Study of Young Open Star Cluster NGC 7790
    Astrophysics (IF 0.67) Pub Date : 2020-06-11
    A. A. Haroon, R. M. Alrehaili, H. A. Ismail

    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 EB-V = 0.512 ± 0.006, EV-R = 0.382 ± 0.005, EJ-H = 0.337 ± 0.001 and EJ-Ks = 0.505

    更新日期:2020-06-11
  • Orbital Solution of Some Contact Binaries
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    M. M. Elkhateeb

    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

    更新日期:2020-06-10
  • Preflare Dynamics of Microwave and Ultraviolet Emission in Active Regions of the Sun
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    I. A. Bakunina, V. F. Melnikov, A. S. Morgachev

    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

    更新日期:2020-06-10
  • Star Formation in thin Disks of Spiral Galaxies Seen Face-On
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    V. E. Karachentseva, I. D. Karachentsev, O. G. Kashibadze

    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

    更新日期:2020-06-10
  • Photometric Studies of the Intermediate Polar DO Dra in 2008 and 2019
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    Ju. V. Babina, E. P. Pavlenko, M. V. Andreev

    An analysis is presented of photometric observations of the intermediate polar DO Dra obtained during an epoch of significant reduction in its outburst activity for different average brightnesses of the system: 13m.6-12m.8 (2008) and 14m.7-14m.3 (2019). The observations in 2008 were made in the Johnson BVR system and in 2019, in integrated light. For the first time in quasi-simultaneous observations

    更新日期:2020-06-10
  • Activity Types of Galaxies Selected from an HRC/BHRC Sample. II
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    G. M. Paronyan, A. M. Mickaelian, H. V. Abrahamyan, G. A. Mikayelyan

    This is a detailed spectral classification of 198 candidate active galactic nuclei (AGN) from a joint HRC/BHRC sample consisting of a combination of the HRC (Hamburg-ROSAT) and BHRC (Byurakan-ROSAT) catalogs. These objects have been identified as optical counterparts of ROSAT x-ray sources, but spectra for 198 of them are given in the SDSS without determinations of their spectral classification. They

    更新日期:2020-06-10
  • Variations in the Period of Negative Superhumps in SU UMa-Type Dwarf Novae. I. Mn Dra (2012-2017)
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    A. S. Sklyanov, E. P. Pavlenko, K. A. Antonyuk, N. V. Pit, V. P. Malanushenko, A. V. Shchurova, A.-M. A. Zaostrozhnykh, S. Yu. Shugarov, A. A. Sosnovskij, Ju. V. Babina, O. I. Antonyuk, A. O. Simon, R. Ya. Zhuchkov, A. G. Gutaev

    This is a photometric study of the dwarf nova MN Dra made during 2012-2017 on nine telescopes over 152 nights. Overall, the observations covered 4 superoutbursts, 7 normal outbursts and the quiescent state. The interval between neighboring superoutbursts in 2017 was 65 days, and between neighboring normal bursts, 15 days. During the superoutbursts of 2012 and 2017, positive superhumps with a period

    更新日期:2020-06-10
  • The Massive Binary System RY Sct – New Solution of the Light Curves
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    N. Kochiashvili, I. Kochiashvili, R. Natsvlishvili, S. Beradze, M. Vardosanidze

    RY Sct is a unique massive binary star system in a short transitional evolutionary phase. It is an eclipsing binary where both stars have overfilled their Roche cavities, so that the system is in an “overcontact” state. It is surrounded by a young circumstellar nebula. The binary is regarded as a rare progenitor of a type WR+OB system. RY Sct is close to the Eddington luminosity limit, so that radiative

    更新日期:2020-06-10
  • Kinematics and Velocity Ellipsoid of Halo Red Giants
    Astrophysics (IF 0.67) Pub Date : 2020-06-10
    M. I. Nouh, W. H. Elsanhoury

    Here, we aim to determine the kinematical properties, velocity ellipsoid and Oort constants using a sample of halo red giants. The study is based mainly on the space and radial velocities of 1583 red giant stars collected from the SEGUE-1 and SEGUE-2 surveys. We divided the sample into three subsamples: the inner halo, the outer halo and the stars near the galactic plane. The fitting of the radial

    更新日期:2020-06-10
  • Two Efficient Computational Algorithms to Solve the Nonlinear Singular Lane-Emden Equations
    Astrophysics (IF 0.67) Pub Date : 2020-04-02
    K. Parand, A. Ghaderi-Kangavari, M. Delkosh

    In this paper, two efficient computational algorithms based on Rational and Exponential Bessel (RB and EB) functions are compared to solve several well-known classes of nonlinear Lane-Emden type models. The problems, which are define in some models of non-Newtonian fluid mechanics and mathematical physics, are nonlinear ordinary differential equations of second-order over the semi-infinite interval

    更新日期:2020-04-02
  • Characteristics of Hot Quark Matter with Neutrino Confinement
    Astrophysics (IF 0.67) Pub Date : 2020-04-01
    G. S. Hajyan

    The MIT quark bag model is used to determine the thermodynamic characteristics of hot strange quark matter that is opaque to neutrinos. Three different variants of the lepton content of hot quark matter are considered. The numerical calculations are done for different temperatures and lepton charge densities. It is shown that in hot (kT~100 MeV) quark matter there are roughly as many neutrinos as massive

    更新日期:2020-04-01
  • Oscillations of Ellipsoidal Solar Active Regions
    Astrophysics (IF 0.67) Pub Date : 2020-03-26
    G. Dumbadze, B. Shergelashvili

    Four active regions (AR) of the sun are studied. Observational data were obtained from directly visible (line of sight) sharp_cea_720s SDO/HMI magnetograms. The data for each AR were processed by a least squares method in an ellipse. Using a sequence of images after processing the data in all the AR, oscillations of the major and minor axes of the ellipse, as well as of the angles of inclination of

    更新日期:2020-03-26
  • Coronal Holes during the Period of Maximum Asymmetry in the 24th Solar Activity Cycle
    Astrophysics (IF 0.67) Pub Date : 2020-03-26
    O. A. Andreeva, V. I. Abramenko, V. M. Malaschuk

    The current 24th solar activity cycle differs substantially from previous cycles in a number of parameters, especially in terms of a large asymmetry in the number of sunspots (Sp) during the second peak of its maximum. From March 2013 through December 2015. a significant predominance was observed in the number of sunspots in the southern hemisphere. The main purpose of this paper is to clarify the

    更新日期:2020-03-26
  • On the Origin of Optical Radiation during the Impulsive Phase of Flares on dMe Stars. I. Discussion of Gas Dynamic Models
    Astrophysics (IF 0.67) Pub Date : 2020-03-26
    E. S. Morchenko

    In connection with a published critique, the author justifies the use of a motionless homogeneous plane layer of pure hydrogen plasma that is near local thermodynamic equilibrium (LTE) for analyzing the characteristics of the radiation from a chromospheric condensation of thickness ∆z=10 km in a gas dynamic model of stellar flares. It is shown that the shock-wave model of flares proposed by Belova

    更新日期:2020-03-26
  • The Program Magreg for Determining the Longitudinal Component of Stellar Magnetic Fields from Spectropolarimetric Observations
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    I. S. Savanov

    The computer program magreg in IDL language has been developed for determining the longitudinal component Bz of the magnetic field of stars. The program has been tested on observations of a number of objects at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAN) using the main stellar spectrograph of the 6-m telescope. The well studied magnetic star γ Equ is used as an

    更新日期:2020-03-25
  • Photometric Investigation of two W UMa Systems
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    M. I. Nouh, M. M. Elkhateeb

    In the present paper, we obtained the first orbital solution for the newly discovered W UMa systems: GSC 3983-0544 and GSC 4502-1040. We used the most recent version of the Wilson-Devinney code to model the light curves of the two systems. The spectral type of the components of the two systems was adopted and the accepted solutions revealed some absolute parameters, which enable us to draw a preliminary

    更新日期:2020-03-25
  • Filaments of the Large Scale Structure and Primary Scalar and Vector Gravitational Perturbations
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    I. K. Rozgacheva, I. B. Kuvshinova

    Published data on the observed properties of the filaments (chains of galaxies and groups of galaxies) which dominate the large-scale structure of the universe are collected. Some of these properties are not described in the standard ΛCDM cosmological model. It is found that the properties of galaxies depend on their position inside or near a filament. The hypothesis is advanced that in the early Universe

    更新日期:2020-03-25
  • Photometric Study of Two Galaxies with X-Structures
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    V. P. Reshetnikov, P. A. Tarakanov, M. V. Kostina

    Data from the SDSS survey are used to study two galaxies with X-structures (UGC 501 and UGC 12253) visible from the edge. Both objects are spiral galaxies of late morphological types with extended stellar disks. The X-structures in the galaxies have different sizes and shapes. The possibility that the different observational parameters of the X-structures in UGC 501 and UGC 12253 are related to different

    更新日期:2020-03-25
  • Study of Rapid Variability of the Blazar OJ 287 in the Radio and Optical Ranges
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    A. Sukharev, M. Ryabov, V. Bezrukovs, A. Orbidans, M. Bleiders, S. Udovichenko, L. Keir, I. Eglitits, P. Dubovsky

    The extragalactic radio source OJ 287 is one of the most studied blazars. A huge amount of data has been accumulated on it (for more than 40 years in the radio range and more than 100 in the optical). Studies of the rapid variability in the radio flux and stellar magnitude of this object with characteristic times ranging from a few hours to several days are of interest in connection with the possible

    更新日期:2020-03-25
  • Panoramic Spectroscopy of Galaxies with Star Formation Regions. A Study of SBS0750+603B
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    S. A. Hakopian, S. N. Dodonov, A. V. Moiseev, A. A. Smirnova

    Details of investigation of SBS0750+603B by providing 3D-spectroscopy are presented as part of a study of a sample of about 350 galaxies of star-formation activity. The observations were made on the 6-m telescope at the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences using the MPFS multi-pupil spectrograph. An analysis of the surface distributions of the major parameters

    更新日期:2020-03-25
  • A Dozen new Dwarf Galaxy Candidates in the Local Volume
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    I. D. Karachentsev, P. Riepe, T. Zilch

    We carried out a survey of low-surface-brightness companions around nine luminous Local Volume galaxies using long exposures with small amateur telescopes. We found 12 low- and very low-surfacebrightness objects around the galaxies, NGC 628, NGC 2337, NGC 3368, NGC 3521, NGC 4236, NGC 4258, NGC 4594, NGC 5055, and NGC 6744, situated within 12 Mpc from us. Assuming the dwarf candidates are satellites

    更新日期:2020-03-25
  • On the Size and Mass of Galaxy Clusters
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    H. M. Tovmassian

    We counted galaxies in the area with 10 Mpc radius around 30 isolated ACO clusters at redshifts z < 0.1. We show that surface densities of galaxies around clusters regularly decrease till 10 Mpc. Separate counts of blue and red galaxies of the cluster environment revealed that at all cluster-centric distances the surface density of red galaxies are higher than that of blue ones. The surface density

    更新日期:2020-03-25
  • Study of Faint Galactic Carbon Stars from the First Byurakan Spectral Sky Survey. IV. GAIA DR2 Data
    Astrophysics (IF 0.67) Pub Date : 2020-03-25
    G. R. Kostandyan

    Data from the second Gaia release (Gaia DR2) are used to analyze and evaluate several important parameters for 127 carbon (C) stars of which 56 are AGB stars of class N and 71 are giants of early CH classes detected in low-dispersion spectral plates from the First Byurakan Survey (FBS). For the FBS C-stars Gaia DR2 G broad – band magnitudes are in the range 9m.4 < G < 18m.2. The radial velocities RV

    更新日期:2020-03-25
  • Activity of the Star bScl Observed by the TESS Space Telescope
    Astrophysics (IF 0.67) Pub Date : 2019-11-28
    I. S. Savanov

    The rotational and flare activity of the chemically peculiar star B9.5IIIpHgMnSi βScl is studied using data from the archive of the TESS space mission. Rotational modulation of the brightness is clearly visible in the light curve of this star, along with two flares that have a structure typical of flares in stars of a later spectral class, with a sharp rise, a peak, and a damping stage. The constructed

    更新日期:2019-11-28
  • Gaseous Components of the Seyfert Galaxy NGC 1275 Nucleus In The Epoch 2012
    Astrophysics (IF 0.67) Pub Date : 2019-11-28
    L. M. Sharipova

    The character of the interaction of two gaseous components which are a structural feature of the nucleus of the Seyfert galaxy NGC 1275 is established during the epoch of a minimum in its activity. A bank of emission line profiles (Hβ and O[III] λ5007Å) obtained from observations on the 1.5-m Russian-Turkish telescope (RTT-150) in January 2012 is used. The physical characteristics (Te, ne) of the emission

    更新日期:2019-11-28
  • Conditions for Formation of the Helium HeI 10830 Å Line in The Disk and Magnetospheric Winds of Young Herbig Ae Stars
    Astrophysics (IF 0.67) Pub Date : 2019-11-28
    T. A. Ermolaeva

    The conditions for formation of helium lines in the disk and magnetospheric winds of Herbig Ae stars are studied. The program package CLOUDY is used to solve this problem. It is shown that the optical thickness of the gas in the HeI 10830 Å line needed to explain the observed P Cyg profiles is reached in the disk or magnetospheric winds of Herbig Ae stars for Te ≥ 10000 K. Here the x-ray emission produced

    更新日期:2019-11-28
Contents have been reproduced by permission of the publishers.
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