Search Publications
Optical Identifications of High-Redshift Galaxy Clusters from the Planck Sunyaev-Zeldovich Survey
Aghanim, N.; Bikmaev, I. F.; Khamitov, I. M. +8 more
We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources (PSZ2) located at high redshifts, z ≈ 0.7-0.9. We used the data of optical observations with the Russian-Turkish 1.5-mtelescope (RTT-150), the Sayan Observatory 1.6-m telescope,…
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…
Low-Frequency Quasi-Periodic Oscillations in the X-ray Nova MAXI J1535-571 at the Initial Stage of Its 2017 Outburst
Grebenev, S. A.; Mereminskiy, I. A.; Semena, A. N. +1 more
We report the discovery of low-frequency quasi-periodic oscillations (QPOs) in the power spectrum of the X-ray nova MAXI J1535-571 at the initial stage of its outburst in September 2017. Based on data from the SWIFT and INTEGRAL instruments, we have traced the evolution of the QPO parameters (primarily their frequency) with time and their correlat…
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 …
An Upper Limit on Nickel Overabundance in the Supercritical Accretion Disk Wind of SS 433 from X-ray Spectroscopy
Medvedev, P. S.; Tsygankov, S. S.; Sazonov, S. Yu. +2 more
We analyze a long (with a total exposure time of 120 ks) X-ray observation of the unique Galactic microquasar SS 433 carried out by the XMM-Newton space observatory with the goal of searching for the fluorescent line of neutral (or weakly ionized) nickel at energy 7.5 keV. We consider two models for the formation of fluorescent lines in the spectr…
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…
Optical Identification of X-ray Sources from the 14-Year INTEGRAL All-Sky Survey
Medvedev, P. S.; Lutovinov, A. A.; Eselevich, M. V. +6 more
We present the results of our optical identifications of several hard X-ray sources from the INTEGRAL all-sky survey obtained over 14 years of observations. Having improved the positions of these objects in the sky with the X-ray telescope (XRT) of the Swift observatory and the XMMNewton observatory, we have identified their counterparts using opt…
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…
X-ray Luminosity Function of Quasars at 3 < z < 5 from XMM-Newton Serendipitous Survey Data
Sazonov, S. Yu.; Khorunzhev, G. A.; Burenin, R. A.
The X-ray luminosity function of distant (3 < z < 5.1) type 1 quasars has been measured. A sample of distant high-luminosity (1045 erg s-1 ≤ L X,2-10 < 7.5×1045 erg s-1 in the 2-10 keV energy band) quasars from the catalog by Khorunzhev et al. (2016) compiled from the data of the 3XMM…