Search Publications
Application of clustering algorithm to wide stellar pairs for unsupervised search of parts of disrupting clusters
Kovaleva, Dana; Sapozhnikov, Sergei
We introduce the application of the clustering algorithm to the preliminary compiled list of probable wide pairs of co-moving stars. The main aim of such development is a possibility of unsupervised blind search of coeval loose stellar structures over significant regions in space. Using Gaia EDR3 data, we investigated the application of the method…
Fitting procedure for estimating interstellar extinction at high galactic latitudes
Malkov, Oleg; Kovaleva, Dana; Avdeeva, Aleksandra +1 more
We determine the interstellar extinction in the selected high-latitude areas of the sky based on Gaia EDR3 astrometry and photometry and spectroscopic data from RAVE survey. We approximate the results with the cosecant law in each area thus deriving the parameters of the barometric formula for different lines of sight. The distribution of the para…
A possible nonthermal X-ray emission from γ Cas analogues stars
Ryspaeva, Elizaveta B.; Kholtygin, Alexander F.
We analyze the archival XMM-Newton X-ray observations of 15 γ Cas analogue stars and two candidates for such objects. The EPIC spectra of the considered stars in the range of 0.2-8 keV were extracted and fitted by different models. Our estimates show that assuming the X-ray emission from γ Cas analogues to be totally thermal, their model plasma te…
Astrometry and photometry of digitized plates of Baldone Schmidt telescope
Eglitis, Ilgmars; Andruk, Vitaly
During the 40-year photographic period of astronomical observations, the Baldone Astrophysical Observatory has accumulated more than 22,000 direct and 2,500 spectral images. In 2018, the digitization of direct astrophoto images with a resolution of 1200 dpi was completed. A processing methodology for obtaining the equatorial coordinates and photom…
Some kinematics of halo coronal mass ejections
Chandra, Ramesh; Verma, Virendra Kumar; Mittal, Nishant
We present an investigation of halo coronal mass ejections (HCMEs) kinematics and other facts about the HCMEs. The study of HCMEs is very important because HCMEs are regarded as the main causes of heliospheric and geomagnetic disturbances. In this study, we have investigated 313 HCMEs observed during 1996-2012 by LASCO, coronal holes, and solar fl…
Conditions for the formation of anomalous tail of comet
Safarov, Abduljalol G.; Ibadinov, Khursand I.
The time and velocity of ejection of dust particles of anomalous tails from cometary nuclei are determined. It is revealed that some comets cause the formation of an anomalous tail is the collision of their comet nucleus with other bodies of the Solar System. An investigation of the formation conditions of the anomalous tail shows that the dust ej…
Spectral energy distributions and colours of hot subluminous stars
Irrgang, Andreas; Heber, Ulrich; Schaffenroth, Johannes
Photometric surveys at optical, ultraviolet, and infrared wavelengths provide ever-growing datasets as major surveys proceed. Colour-colour diagrams are useful tools to identify classes of star and provide large samples. However, combining all photometric measurements of a star into a spectral energy distribution will allow quantitative analyses t…
Thermal Evolution of the Nucleus of the Comet 67P for 120 Years: Numerical Simulations
Rusol, Andrey V.; Dorofeeva, Vera A.
The purpose of this paper is to estimate to what temperatures and to what depth the outer layers of the cometary nuclei are heated for several dozen revolutions around the Sun, and what changes in the composition of the volatiles occur in this case. This is important because it is not clear how much the experimentally obtained results on the compo…
Spectral analysis of the He-enriched sdO-star HD 127493
Heber, Ulrich; Dorsch, Matti; Latour, Marilyn
The bright sdO star HD127493 is known to be of mixed H/He composition and excellent archival spectra covering both optical and ultraviolet ranges are available. UV spectra play a key role as they give access to many chemical species that do not show spectral lines in the optical, such as iron and nickel. This encouraged the quantitative spectral a…
Meet the family - the catalog of known hot subdwarf stars
Gänsicke, Boris T.; Telting, John H.; Østensen, Roy H. +6 more
In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, class…