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Babyk I.,Taras Shevchenko National University | Elyiv A.,Main Astronomical Observatory of NAS of Ukraine | Elyiv A.,Institute Dastrophysique Et Of Geophysique | Melnyk O.,Institute Dastrophysique Et Of Geophysique | And 2 more authors.
Kinematics and Physics of Celestial Bodies | Year: 2012

The mass distribution for the galaxy cluster Abell 2744 (z = 0. 308) is investigated on the base of the archival X-ray data of the Chandra observatory. The temperature of the hot gas in the cluster (kT = 9.82 -0.41 +0.43 keV) and the cluster total mass (M 200 = 2.22 -0.12 +0.13 × 10 15M ⊙) for the radius R 200 = 2.38 -0.31 +0.36 Mpc are estimated. The density and mass profiles for the intergalactic gas and dark matter are obtained. The fractions of the intergalactic gas and dark matter in the total mass of the cluster are 15.4 -1.3 +1.3% and 84.6 -1.3 +1.4%, respectively. © 2012 Allerton Press, Inc.

Neslusan L.,Slovak Academy of Sciences | Ivanova O.,Main Astronomical Observatory of NAS of Ukraine | Husarik M.,Slovak Academy of Sciences | Svoren J.,Slovak Academy of Sciences | Krisandova Z.S.,Slovak Academy of Sciences
Planetary and Space Science | Year: 2016

Photometric observations of asteroid (596) Scheila were obtained during and after its 2010 outburst. The estimated radius of the body (spherical approximation of the asteroidal body) was 51.2±3.0. km and 50.6±3.0. km for different methods. The ejected dust mass from the asteroid ranged from 2.5×107 to 3.4×107kg for different methods. An impact mechanism for triggering Scheila's activity is discussed. A few days before the impact, Scheila passed through the corridors of two potential cometary streams. © 2016 Elsevier Ltd.

Ivanova O.V.,Main Astronomical Observatory of NAS of Ukraine | Neslusan L.,Slovak Academy of Sciences | Svoren J.,Slovak Academy of Sciences | Seman Krisandova Z.,Slovak Academy of Sciences
Icarus | Year: 2015

We attempt to answer two questions concerning the impacts of stream meteoroids on the nuclei of Comets 9P/Tempel 1 and 81P/Wild 2: firstly, how many streams cross the orbits of both comets and, secondly, what is the index of the differential mass distribution of impactors, s, when we assume that a prevailing number of the craters on the surfaces of cometary nuclei were created by stream meteoroids? We found that 110 and 129 potential streams originating from comets likely cross the orbits of 9P and 81P, respectively (and 103 potential streams cross the orbit of 1P/Halley, for comparison). If we consider the more compact streams originating from asteroids, the 9P and 81P pass through such streams 15 664 and 65 368 times. Neither these large numbers of passages imply, however, enough large impactors to excavate the whole observed variety of craters on studied comets. For all craters on 9P and 81P, s=. 2.09. ±. 0.01 and s=. 2.25. ±. 0.03, respectively. The craters on 81P seem to be, however, excavated by the impactors from four discernible sources. For two numerous enough sources we find s=. 5.6. ±. 0.2 and s=. 5.2. ±. 0.5. The difference between the indices for the set of all craters and the sets of their partial groups obviously implies an unknown cosmogonic consequence. © 2015 Elsevier Inc.

Polosukhina N.,Crimean Astrophysical Observatory | Shavrina A.,Main Astronomical Observatory of NAS of Ukraine | Drake N.A.,State University of Rio de Janeiro | Smirnova M.,Crimean Astrophysical Observatory
Memorie della Societa Astronomica Italiana, Supplementi - Journal of the Italian Astronomical Society, Supplement | Year: 2012

We discuss lithium abundance and 6Li/7Li isotopic ratio in atmospheres of some magnetic roAp stars. Overabundances of the lithium were found in atmospheres of some roAp stars based on the analysis of both lithium lines at 6104 Å and 6708 Å as well as the high values of the 6Li/7Li isotopic ratio (0.2-0.5). These facts can be explained by lithium production in spallation reactions on stellar surface and by preserving 7Li and 6Li isotopes to be destroyed in the inner layers of stellar atmospheres by strong magnetic fields near magnetic poles. Our synthetic spectrum calculations take into account magnetic line broadening effects. © SAIt 2012.

Shulyak D.,University of Gottingen | Shavrina A.,Main Astronomical Observatory of NAS of Ukraine | Lyashko D.,Taurida National University | Drake N.A.,State University of Rio de Janeiro | And 2 more authors.
Proceedings of the International Astronomical Union | Year: 2014

High-resolution spectra obtained with the 6m BTA telescope, Russia, and with HARPS and VLT/UVES telescopes at ESO, Chile, were used for Doppler Imaging analysis of two roAp stars, HD 12098 and HD 60435, showing strong and variable Li resonance line in their spectra. We found that Li has highly inhomogeneous distribution on the surfaces of these stars. We compared our results with previously obtained Doppler Imaging mapping of two CP2 stars, HD 83368 and HD 3980, and discuss the correlation between the position of the high Li-abundance spots and magnetic field. © International Astronomical Union 2014.

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