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Distortion of the stellar velocity field parameters due to systematic variations of parallaxes over the celestial sphere
Tsvetkov, A. S.; Vityazev, V. V.
We study the effect of systematic variations in stellar parallaxes over the celestial sphere on the results of a kinematic analysis of stellar proper motions. Our approach is based on the representation of stellar parallaxes by scalar spherical harmonics and on the decomposition of stellar proper motions into a system of vector spherical harmonics…
Aperiodic X-ray flux variability of EX Hya and the area of the base of the accretion column at the white dwarf surface
Revnivtsev, M. G.; Semena, A. N.
The goal of this paper is to determine the characteristic cooling time of the accretion flowmatter near the surface of the magnetic white dwarf in the binary system EX Hya. Most of the X-ray photons in such binary systems are produced in an optically thin hot plasma with a temperature above 10 keV heated when the matter passes through the shock ne…
Stellar content of the interacting galaxies IC 1727 and NGC 672
Tikhonov, N. A.; Galazutdinova, O. A.; Lebedev, V. S.
Based on archival Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for an isolated pair of interacting galaxies, IC 1727 and NGC 672, and constructed their Hertzsprung-Russell diagrams. The galaxy IC 1727 exhibits a strong asymmetry in the apparent distribution of young stars. The distribution of old stars is smoother an…
Velocity of the local interstellar medium relative to the sun from interstellar helium flux measurements onboard the Ulysses and IBEX spacecraft
Katushkina, O. A.; Izmodenov, V. V.; Provornikova, E. A.
The question of determining the relative velocity of the local interstellar medium (LISM) based on direct interstellar helium flux measurements in the Solar system is considered. Such measurements were made onboard the Ulysses spacecraft in 1990-2007 at a distance of 2-5 AU from the Sun and have been made from 2009 to the present day onboard the I…
Method of ignoring the systematic variations of stellar parallaxes over the celestial sphere in a kinematic analysis of stellar proper motions
Tsvetkov, A. S.; Vityazev, V. V.
A method for determining the velocity field parameters free from the distortions due to the systematic variations of stellar parallaxes over the celestial sphere is proposed. The method is based on the approximation of parallaxes as a function of coordinates on the sphere using spherical harmonics and can be applied in those cases where the solar …