Search Publications
Surprising Variability of the Planetary Nebula IC 4997 = QV Sge
Arkhipova, V. P.; Esipov, V. F.; Ikonnikova, N. P. +3 more
We 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 …
Orbits and Structure of the Quadruple Systems GJ 225.1 and FIN 332
Tokovinin, A.
Only a handful of quadruple systems with two accurate inner visual orbits are known. The architecture of two such systems is studied here to determine the period ratios, mutual orbit orientation, and other parameters; updated orbital elements and their errors are derived. Gliese 225.1 (HIP 28442) is composed of three K-type and one M-type dwarfs a…
Kinematics of T Tauri Stars Close to the Sun from the Gaia DR2 Catalogue
Bobylev, V. V.
The 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 $350× 270× 87$ pc and it is oriented at an angle of $14^{\circ}± 1^{\ci…
Changes in the Period of the Population II Cepheid CC Lyr
Berdnikov, L. N.; Pastukhova, E. N.; Yacob, A. M.
The reduction of all the available photometry for the Cepheid CC Lyr has allowed its $O-C$ diagram spanning a time interval of 124 years to be constructed. The data obtained provide evidence for the existence of large random fluctuations in the period ($\varepsilon/P≈ 0.046$). A formal fitting of the $O-C$ residuals has made it possible to estimat…
The First Orbits of Six Wide Double Stars in the Solar Neighborhood Based on Gaia DR2 Observations
Romanenko, L. G.; Kiyaeva, O. V.
The apparent motion parameter (AMP) method is designed to determine the orbits of wide pairs of double stars with orbital periods of hundreds and thousands of years. This is a dynamical method using all that is known about the star at one moment to reconstruct its complete orbit within the two-body problem. The Gaia DR2 catalog contains all of the…
Search for Evolutionary Changes in the Period the Cepheid ET Vul
Berdnikov, L. N.; Pastukhova, E. N.
The 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, $dP/dt=-426.5(±{29.7})$ s yr${}^{-1}$, in agreement with the results of model calculat…
Optical Identification of Four Hard X-ray Sources from the INTEGRAL Sky Surveys
Medvedev, P. S.; Sazonov, S. Yu.; Eselevich, M. V. +8 more
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 infrar…
Search for Evolutionary Changes in the Period of the Classical Cepheid EV Aql
Berdnikov, L. N.
The reduction of all the available photometry for the Cepheid EV Aql has allowed its $O-C$ diagram spanning a time interval of 130 years to be constructed. This has made it possible to calculate the rate of evolutionary decrease in the period, $dP/dt=-33.2({±}{6.9})$ s yr${}^{-1}$, in agreement with the results of model calculations for the second…
Investigation of the Kinematics of Stars from the Gaia Data Release 2 with Radial Velocities Catalogue Using Scalar and Vector Spherical Harmonics
Tsvetkov, A. S.; Amosov, F. A.; Petrov, S. D. +1 more
This 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 ha…
Spectroscopy of B and Be Stars in the Young Open Star Cluster NGC 581 (M 103)
Tarasov, A. E.
Based on moderate-resolution spectra in the range 4200-5200 Å, we have studied B and Be stars in the young open star cluster NGC 581. The temperatures of the program stars have been derived by the differential method with the choice of simple spectroscopic parameters for a number of lines and their comparison with the analogous parameters of a lar…