Search Publications

Interrelationships between Halo-Type Coronal Mass Ejections and Solar Flares Based on Observations in the 23rd and 24th Cycles

Bruevich, E. A.; Burov, V. A.; Arakelov, A. S. +1 more

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…

Orbits and Individual Masses of Some Visual Binaries

Elsanhoury, W. H.; Elkholy, E. A.; Nouh, M. I.

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 e…

Study of Faint Galactic Carbon Stars from the First Byurakan Spectral Sky Survey. IV. GAIA DR2 Data

Kostandyan, G. R.

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…

Study of the Binary Star ADS 7251 by Observations on the 65-cm Refractor at Pulkovo from 1962-2018

Romanenko, L. G.; Izmailov, I. S.; Shakht, N. A. +1 more

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…

Dwarf Spheroidal Galaxies in the M101 Group and Behind it

Karachentsev, I. D.; Makarova, L. N.

We use images from the Hubble Space Telescope to determine the distances to a dozen objects with low surface brightness recently observed around the bright nearby spiral M101. Only two dwarf galaxies, M101-DwA and M101-Dw9, turn out to be actual satellites of M101 at distances of about 7 Mpc. The other objects are probably members of a distant gro…

New Carbon Stars Confirmed in the Digitized First Byurakan Survey Database

Gigoyan, K. K.; Gigoyan, K. S.; Kostandyan, G. R. +2 more

X-Ray Warm Absorber Variability of the Seyfert Galaxy Arakelian 564

Nouh, M. I.; Korany, B.

We studied the variability of warm absorber clouds of ionized gas within AGN for the Seyfert 1 galaxy Arakelian 564. The X-ray spectra for four XMM-Newton observations of this object are analyzed using the EPIC and the RGS instruments. These four observations covered 11 years. The ionization parameter ξ of the absorbing matter changed between obse…

New Carbon Stars in the Catalina Catalog of Periodic Variables

Mauron, N.; Gigoyan, K. K.; Gigoyan, K. S. +5 more

This study is about carbon stars detected in a program of spectral type determinations for a large amount of optically faint periodic variables. These variables are taken from the Catalina Survey Data Release-1 (CSDR1) data set. As much as 967 objects were studied. Spectral classification uses the objective-prism scanned plates of the Hamburg Quas…

Galactic Kinematics Derived From Data in the RAVE5, UCAC4, PPMXL, and Gaia TGAS Catalogs

Bobylev, V. V.; Bajkova, A. T.; Tsvetkov, A. S. +1 more

The three-dimensional velocities of stars with high-precision positions, proper motions, and parallaxes from the Gaia TGAS catalog and radial velocities from the RAVE5 catalog are examined. A sample of 92395 stars with estimated ages yields the following kinematic parameters: (U, V, W)=(9.42, 20.34, 7.21)±(0.12, 0.10, 0.09) km/s, Ω = 26.29 ± 0.39 …

Fractality of Isotherms of the Cosmic Microwave Background Based on Data from the Planck Spacecraft

Mylläri, A. A.; Raikov, A. A.; Orlov, V. V. +3 more

A system of isophotes of the cosmic microwave background (CMB) is constructed for several regions on the celestial sphere using data from the Planck spacecraft. The fractal dimensionality of the isotherms is estimated to be D_c ≈ 1.78 ± 0.03. Our results agree with earlier work based on the ILC charts with WMAP data. Our simulations conf…