Search Publications
Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue
Bobylev, V. V.; Bajkova, A. T.
We have selected and analyzed a sample of OB stars with known line-of-sight velocities determined through ground-based observations and with trigonometric parallaxes and propermotions from the Gaia DR2 catalogue. Some of the stars in our sample have distance estimates made from calcium lines. A direct comparison with the trigonometric distance sca…
Measuring the Probabilistic Photometric Redshifts of X-ray Quasars Based on the Quantile Regression of Ensembles of Decision Trees
Meshcheryakov, A. V.; Glazkova, V. V.; Gerasimov, S. V. +1 more
We present empirical machine learning algorithms for measuring the probabilistic photometric redshifts (photo-z) of X-ray quasars based on the quantile regression of ensembles of decision trees. Relying on the data of present-day photometric sky surveys (e.g., SDSS, GALEX, WISE, UKIDSS, 2MASS, FIRST), the proposed methods allow one to make high-qu…
Influence of Inelastic Collisions with Hydrogen Atoms on Non-LTE Oxygen Abundance Determinations
Sitnova, T. M.; Mashonkina, L. I.
We present the results of our modeling of the O I line formation under non-LTE conditions in the atmospheres of FG stars. The statistical equilibrium of O I has been calculated using Barklem's quantum-mechanical rates of inelastic collisions with hydrogen atoms. We have determined the non-LTE oxygen abundance from atomic O I lines for the Sun and …
Kinematics of Stars from the TGAS (Gaia DR1) Catalogue
Tsvetkov, A. S.; Vityazev, V. V.; Popov, A. V. +3 more
Based on the stellar proper motions of the TGAS (Gaia DR1) catalogue, we have analyzed the velocity field of main-sequence stars and red giants from the TGAS catalogue with heliocentric distances up to 1.5 kpc. We have obtained four variants of kinematic parameters corresponding to different methods of calculating the distances from the parallaxes…
Searching for Binary Systems Among Nearby Dwarfs Based on Pulkovo Observations and SDSS Data
Izmailov, I. S.; Khovrichev, M. Yu.; Apetyan, A. A. +9 more
Our goal is to find previously unknown binary systems among low-mass dwarfs in the solar neighborhood and to test the search technique. The basic ideas are to reveal the images of stars with significant ellipticities and/or asymmetries compared to the background stars on CCD frames and to subsequently determine the spatial parameters of the binary…
Testing the Distance Scale of the Gaia TGAS Catalogue by the Kinematic Method
Bobylev, V. V.; Bajkova, A. T.
We have studied the simultaneous and separate solutions of the basic kinematic equations obtained using the stellar velocities calculated on the basis of data from the Gaia TGAS and RAVE5 catalogues. By comparing the values of Ω'0 found by separately analyzing only the line-of-sight velocities of stars and only their proper motions, we …
Searching for the Young Kinematic Group Associated with HD 166191
Eselevich, M. V.; Sokolov, I. V.; Potravnov, I. S. +1 more
We present the results of our search for the stars kinematically related to the young star HD 166191 surrounded by a warm dust disk. Using data from the GAIA DR1, 2RXS, ALLWISE catalogues and confirming optical spectroscopy, we have identified five stars of age 10 Myr with similar kinematics in a sky region of radius 11° on the periphery of the Sc…
Kinematics and Dynamics of the Galactic Halo from RR Lyrae Variable Stars
Dambis, A. K.; Zhao, G.; Rastorguev, A. S. +3 more
Based on a sample of RR Lyrae variable stars including more than 9000 objects with proper motions and distances, we have investigated the kinematics of the Galactic halo from the two-dimensional velocity field. We have used both the proper motions deduced independently by us from the positional data taken from all-sky catalogues in a time interval…
New Features of Parenago's Discontinuity from Gaia DR1 Data
Tsvetkov, A. S.; Vityazev, V. V.; Popov, A. V. +3 more
The velocity field of main-sequence stars and red giants from the TGAS catalogue with heliocentric distances up to 1.5 kpc has been analyzed for various spectral types. To estimate the influence of a low accuracy of stellar parallax measurements on the results of a kinematic analysis of distant stars, first we have studied in detail how the kinema…
Kinematics of B-F Stars as a Function of Their Dereddened Color from Gaia and PCRV Data
Gontcharov, G. A.
Parallaxes with an accuracy better than 10% and proper motions from the Gaia DR1 TGAS catalogue, radial velocities from the Pulkovo Compilation of Radial Velocities (PCRV), accurate Tycho-2 photometry, theoretical PARSEC, MIST, YaPSI, BaSTI isochrones, and the most accurate reddening and interstellar extinction estimates have been used to analyze …