Asteroid observations at low phase angles. I. 50 Virginia, 91 Aegina and 102 Miriam     

V.G. Shevchenko  I.N. Belskaya  V.G. Chiorny  J. Piironen  A. Erikson  G. Neukum  R. Mohamed 《Planetary and Space Science》1997,45(12):1615-1623

We present observations of magnitude-phase dependences of three low-albedo asteroids down to phase angles of 0.1–0.2°. Data were obtained during 40 nights from 1994 to 1995 within the joint observational program at ESO and Kharkiv Astronomical Observatories with the aim to reach as low phase angles as possible. All three low-albedo asteroids may display a small nonlinear increase in magnitude-phase dependence at subdegree phase angles. The phase curves of 50 Virginia and 102 Miriam are poorly approximated by the HG function. Rotation periods of the asteroids were also determined: 14.310±0.010 hours for 50 Virginia, 6.030±0.001 h for 91 Aegina and 15.789± 0.003 h for 102 Miriam.  相似文献   

The stellar composition of the star formation region CMa R1 – III. A new outburst of the Be star component in Z CMa     

M. E. van den Ancker  P. F. C. Blondel  H. R. E. Tjin A Djie  K. N. Grankin  O. V. Ezhkova  V. S. Shevchenko  E. Guenther  B. Acke 《Monthly notices of the Royal Astronomical Society》2004,349(4):1516-1536

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The stellar composition of the star formation region CMa R1 – II. Spectroscopic and photometric observations of nine young stars     

H.R.E. Tjin A Djie  M.E. van den Ancker  P.F.C. Blondel  V.S. Shevchenko  O.V. Ezhkova  D. de Winter  K.N. Grankin 《Monthly notices of the Royal Astronomical Society》2001,325(4):1441-1457

We present new high- and low-resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD 52721, HD 53367, LkH α  220 and LkH α  218) show H α emission and we argue that they are Herbig Be stars with discs. Our photometric and spectroscopic observations of these stars reveal new characteristics of their variability. We present first interpretations of the variability of HD 52721, HD 53367 and the two LkH α stars in terms of a partially eclipsing binary, a magnetic activity cycle and circumstellar dust variations, respectively. The remaining five stars show no clear indications of H α emission in their spectra, although their spectral types and ages are comparable with those of HD 52721 and HD 53367. This indicates that the presence of a disc around a star in CMa R1 may depend on the environment of the star. In particular we find that all H α emission stars are located at or outside the arc-shaped border of the H  ii region, which suggests that the stars inside the arc have lost their discs through evaporation by UV photons from nearby O stars, or from the nearby (<25 pc) supernova, about 1 Myr ago.  相似文献   

Ore-bearing hydrothermal metasomatic processes in the Elbrus volcanic center, the northern Caucasus, Russia     

A. G. Gurbanov  O. A. Bogatikov  A. Ya. Dokuchaev  V. M. Gazeev  S. S. Abramov  E. O. Groznova  A. V. Shevchenko 《Geology of Ore Deposits》2008,50(3):199-217

Precaldera, caldera, and postcaldera cycles are recognized in the geological evolution of the Pleistocene-Holocene Elbrus volcanic center (EVC). During the caldera cycle, the magmatic activity was not intense, whereas hydrothermal metasomatic alteration of rocks was vigorous and extensive. The Kyukyurtli and Irik ore-magmatic systems have been revealed in the EVC, with the former being regarded as the more promising one. The ore mineralization in rocks of the caldera cycle comprises occurrences of magnetite, ilmenite, pyrite and pyrrhotite (including Ni-Co varieties), arsenopyrite, chalcopyrite, millerite, galena, and finely dispersed particles of native copper. Pyrite and pyrrhotite from volcanics of the caldera cycle and dacite of the Kyukyurtli extrusion are similar in composition and differ from these minerals of the postcaldera cycle, where pyrite and pyrrhotite are often enriched in Cu, Co, and Ni and millerite is noted as well. The composition of ore minerals indicates that the hydrothermal metasomatic alteration related to the evolution of the Kyukyurtli hydrothermal system was superimposed on rocks of the caldera cycle, whereas the late mineralization in rocks of the postcaldera cycle developed autonomously. The homogenization temperature of fluid inclusions in quartz and carbonate from crosscutting veinlets in the apical portion of the Kyukyurtli extrusion is 140–170°C and in quartz from geyserite, 120–150°C. The temperature of formation of the chalcopyrite-pyrite-pyrrhotite assemblage calculated using mineral geothermometers is 156 and 275°C in dacite from the middle and lower portions of the Malka lava flow and 190°C in dacite of the Kyukyurtli extrusion. The hydrothermal solutions that participated in metasomatic alteration of rocks pertaining to the Kyukyurtli ore-magmatic system (KOMS) and formed both secondary quartzite and geyserite were enriched in fluorine, as evidenced from the occurrence of F-bearing minerals-zharchikhite, ralstonite, α-ralstonite, and fluorite-identified in these metasomatic rocks for the first time. By analogy with porphyry Cu-Mo deposits in Chile and the United States, the ore mineralization of the KOMS may be classified by composition and textural and structural attributes as a supraore level of porphyry copper genetic type. The volcanic rocks of the KOMS and the EVC as a whole are enriched in Ag, Mo, Zn, As, Sb, Se, and Ba. Judging from the scale of argillic alteration and taking into account the data on porphyry Cu-Mo ore-magmatic systems of the Greater Caucasus, veined Pb-Zn ore mineralization may be expected in the propylitic zone at a depth down to 1000 m from the present-day erosion level of the KOMS. Stringer-disseminated Au-Ag, Cu, and Cu-Mo ore mineralization of the upper part of the porphyry ore-magmatic system related to subvolcanic dacitic intrusions may be localized somewhat deeper.  相似文献   

Instrumental measurements of 2009–2011 tsunamis on the Russian Pacific coast     

G. V. Shevchenko  T. N. Ivelskaya  A. V. Loskutov 《Izvestiya Atmospheric and Oceanic Physics》2014,50(5):459-473

We describe the progress (since 2008) in the development of the network of autonomous bottom stations of the Institute of Marine Geology and Geophysics, Far East Branch, Russian Academy of Sciences (IMGG FEB RAS), and telemetry recorders of the Tsunami Warning Service (TWS) on the Pacific coast of Russia. We show that these instrumental measurements are important for operational tsunami warning and performing an a posteriori study of tsunami manifestation features. The characteristics of the Samoan (2009), Chilean (2010), and Tohoku (2011) tsunamis in different areas of the Russian Far East coast are examined.  相似文献   

Sweeping-out of dust from spiral galaxy as a result of “magnetic sling” effect     

Yu. N. Mishurov  I. A. Acharova  M. G. Shevchenko  D. A. Tyshlangov 《Astrophysical Bulletin》2014,69(1):21-26

A new mechanism of sweeping out of dust grains beyond galactic disks both in the radial direction along the galactic plane and in the vertical, cross-disk direction is proposed. The mechanism is driven by the interaction of dust grains with the bisymmetric nonstationary magnetic field of the galaxy, whose lines are curved and corotate with the stellar spiral density wave responsible for the arms. We attribute the radial transfer of interstellar dust grains in the plane of galactic disks to the fact that charged dust grains are “glued” to magnetic field lines and are therefore pushed outward because of the rotation of magnetic field lines and their tilt with respect to the radial direction parallel to the disk plane. In addition, dust is swept out vertically in the cross-disk direction because of the drift motion in crossed magnetic and gravitational fields (both are parallel to the galactic plane). Numerical computations of the motion of dust grains in real magneto-gravitational fields with the allowance for the drag force from interstellar gas show that the time scale of dust grain transport beyond galactic disks is on the order of 1 Gyr or shorter.  相似文献   

The River–Sea Transition Zone (Marginal Filter) of the Northern Dvina River as an Effective Trap of Riverine Sedimentary Matter on Its Way to the Open Area of the White Sea     

Gordeev  V. V.  Shevchenko  V. P.  Novigatsky  A. N.  Kochenkova  A. I.  Starodymova  D. P.  Lokhov  A. S.  Belorukov  S. K.  Yakovlev  A. E. 《Oceanology》2022,62(2):221-230

Oceanology - The article presents the results of generalizing the data of 20 years of research in the river–sea transition zone of the Northern Dvina River and White Sea (marginal filter...  相似文献   

Dispersed organic matter and its fluxes in oceans and seas from the example of the White Sea: Results of a 12-year study     

A. P. Lisitsyn  A. N. Novigatskii  V. P. Shevchenko  A. A. Klyuvitkin  M. D. Kravchishina  A. S. Filippov  N. V. Politova 《Doklady Earth Sciences》2014,456(1):635-639

Annual and long-term quantitative estimations of the vertical fluxes of sedimentary matter in the White Sea are the basis for direct calculations of the gain of chemical components and minerals and diverse pollution of the surface layer of the bottom sediments. The White Sea, one of six Russian Arctic seas, may be considered as a megapolygon for further modern study using the new mechanisms of Arctic sedimentogenesis discovered. This work is directed at elaboration of new technologies of complex study of seas using submarine sedimentation and regular vessel observatories. The first priority task is year-round monitoring along the Northern Sea route.  相似文献   

Subsea uplifts origin of the Rugozerskaya bay and the Great Salma channel (Kandalaksha Bay)     

Y. E. Terekhina  M. Y. Tokarev  N. V. Shevchenko  N. A. Kozupitsa 《Moscow University Geology Bulletin》2017,72(3):209-214

The origin of the subsea uplifts of the Rugozerskaya bay and the Great Salma strait is discussed in this article. It was found that the present-day bottom surface of the investigation area imitates the post-glacial terrain. This was determined by accumulative glacial formations that were emulated with post-glacial sedimentation processes. All modern bottom uplifts are similar to the ancient post-glacial terrain. Most presentday bottom surface depressions are similar to post-glacial surface inequalities, but the configuration of modern closed kettles could be changed via glacial–marine sedimentation and other processes.  相似文献