Optical variability of the NLS1 galaxy Ark 564 in 1987–2004     

V. T. Doroshenko  S. G. Sergeev  C. M. Gaskell  Yu. V. Golubinskii  E. S. Klimek  E. A. Sergeeva 《Astronomy Reports》2006,50(9):708-713

We present the results of our U BV R _c I _c photoelectric and CCD photometry of the NLS1 galaxy Ark 564 in 1987–2004. Between late 1997 and 2002, a slight increase in brightness was observed followed by a small but systematic decline until 2004. Ark 564 has a low variability amplitude, within 0.2^m in the U BV R _c I _c bands. The galaxy’s spectral energy distribution at 3600–9000 Å is unlike those for Seyfert 1 (Syl) galaxies. A delay of the Ic flux relative to the B flux of about three days was found, which is in agreement with the standard disk model. This delay probably reflects the geometric size of the region that emits the observed continuum.  相似文献   

Specific Compositional Features of Sediments from the Haakon Mosby Mud Volcano,Southwestern Barents Sea     

Krupskaya  V. V.  Andreeva  I. A.  Sergeeva  E. I.  Cherkashev  G. A. 《Lithology and Mineral Resources》2002,37(2):130-137

The submarine Haakon Mosby mud volcano was studied in detail during several cruises, resulting in the collection of an abundant and diverse lithological material. Comprehensive field and laboratory studies made it possible to identify different types of sediments with specific granulometric and pelite fraction (<0.005 mm) compositions, as well as the regularity of their spatial distribution relative to various morphostructural zones of the mud volcano.  相似文献   

<Emphasis Type="Italic">BVRI</Emphasis> CCD-photometry of comparison stars in the neighborhoods of galaxies with active nuclei. III     

V. T. Doroshenko  S. G. Sergeev  Yu. S. Efimov  S. Nazarov  V. I. Pronik  E. A. Sergeeva  G. A. Sivtsov 《Astrophysics》2007,50(1):40-53

Observations with a matrix photometer are reported. The stellar magnitudes in the BVRcIc bands are estimated for 80 comparison stars in the neighborhoods of 10 galaxies with active nuclei: 2 Seyfert galaxies, 4 quasars, and 4 BL Lac objects. The stellar magnitudes of the observed stars range from 11 to 19^m.5. For stars with magnitudes of 14–15^m the typical photometric errors are 0^m.011, 0^m.008, 0^m.006, and 0^m.007 in the B, V, R, and I bands, respectively. The BVRI magnitudes for most of these stars were not known previously. 14′ × 14′ finding charts for these stars are included. These results can be used for differential BVRI photometry of active galactic nuclei. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 57–72 (February 2007).  相似文献   

Feeding and distribution of zooplankton in the desalinated “lens” in the Kara Sea: Impact of the vertical salinity gradient     

A. F. Pasternak  A. V. Drits  G. A. Abyzova  T. N. Semenova  V. M. Sergeeva  M. V. Flint 《Oceanology》2015,55(6):863-870

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Physical conditions in the plasma tail of comet C/1987 P1 bradfield     

S. A. Borysenko  Yu. V. Sizonenko  I. V. Luk’yanyk  A. V. Ivanova  A. D. Voitsekhovskaya  T. P. Sergeeva  A. V. Golovin 《Kinematics and Physics of Celestial Bodies》2011,27(2):92-97

Photometric measurements of photographic images of comet C/1987 P1 Bradfield have been carried out with a flat-bed scanner equipped with a slide module. Lengthwise and transverse photometric profiles of the cometary plasma tail have been obtained. Magnetic field induction and some other physical characteristics of the cometary plasma tail observed in November 1987 have been estimated with the use of the diffusion model for a cometary tail by Shul’man and Nazarchuk (1968). It has been shown that the scanned images of comets can be used for estimating the physical characteristics of cometary tails.  相似文献   

On the cause of the discrepancy between groundbased and spaceborne lightcurves of Ganymede and Callisto in the <Emphasis Type="Italic">V</Emphasis> band     

V.?V.?Prokof’eva-MikhailovskayaEmail author  A.?N.?Abramenko  G.?V.?Baida  A.?V.?Zakrevskii  L.?G.?Karachkina  E.?A.?Sergeeva  E.?A.?Zhuzhulina 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):68-81

Properties of the surfaces of Jupiter’s satellites—Ganymede and Callisto—are shortly described. Their images acquired in space missions are shown. Causes of the discrepancy between orbital lightcurves of the satellites obtained from the earth and spaceborne maps of the satellites are considered. The groundbased observations were carried out under phase angles of solar illumination ranging from 0° to 12°, and the maps were built from images acquired from spacecraft in a wide interval of solar phase angles. We suggest that the main cause of the discrepancies between the lightcurves is the coherent backscattering effect observed only at small phase angles of the sun.  相似文献   

Volcanogenic massive sulfide deposits of ophiolite associations     

A. L. Dergachev  N. I. Eremin  N. E. Sergeeva 《Moscow University Geology Bulletin》2010,65(5):265-272

Volcanogenic massive sulfide deposits in ophiolite complexes are usually attributed to the Cyprus type. They associate with basaltic volcanics that are formed in mid-ocean or back-arc spreading centers and much less frequently in intra-plate settings. The deposits are characterized by copper or copper-zinc ores that are enriched in Ni, Co, and in places Mn and As, but are very poor in Pb and demonstrate a low to moderate content of Ag and Au. Typically, the deposits are low to very low in ore and metal reserves. Cyprus-type deposits were irregularly distributed during geological history. The most ancient of them were formed in the Neoproterozoic, while the bulk of the deposits are Ordovician or Cretaceous in age. Their possible Paleoproterozoic analogues can be found in the Svecofennian belt (Outokumpu ore district), while modern ones are confined to the Explorer and Endeavour Ridges and southern segment of the Juan de Fuca Ridge.  相似文献   

Phytoplankton Community Structure in the Polar Front of the Eastern Barents Sea at the End of the Growth Season     

V. M. Sergeeva  L. S. Zhitina  S. A. Mosharov  A. A. Nedospasov  A. A. Polukhin 《Oceanology》2018,58(5):700-709

Phytoplankton community and its distribution were investigated in the south part of the Polar Front in the eastern Barents Sea in October 2014. Analysis of the spatial differences in the phytoplankton structure was performed in connection with changes of the temperature, salinity and biogenic regime. At the end of the growing season in the phytoplankton community was dominated by destruction processes and the concentration of nutrients in the upper mixed layer was higher than the limiting level. Coccolithophores (Emiliania huxleyi and Discosphaera cf. tubifer) dominanted over investigated area. The maximum values of abundance and biomass of coccolithophores reached 90.4 mln.cell/m³ and 30.8 mgC/m³, drawing up 82% of the total number and 93% of the total biomass of phytoplankton. Influence of transformed the waters of Atlantic origin was observed in the western part of the investigated area. The number of species in the phytoplankton community here was 1.5–2 times lower than in the eastern part of the occupied mostly by Barents Sea water. In the eastern part of the presence of large dinoflagellates Neoceratium spp. (Ceratium spp.) and Dinophysis spp., lower values of chlorophyll a concentration, a higher proportion of pheophytin in the amount of pigment chlorophyll + pheophytin, the high content of ammonia in the upper mixed layer showed that in this area the phytoplankton was at a later seasonal succession stage than the western part.  相似文献   

Age and origin of rocks of the Daldyn Group of the Anabar Shield: Evidence from U-Pb zircon dating,Sm-Nd and Lu-Hf isotope systematics     

L. Yu. Sergeeva  N. I. Gusev  K. I. Lokhov  V. A. Glebovitskii 《Geochemistry International》2017,55(4):380-383

The Hf-Nd isotope systematics was used to determine the genesis of zircons from granulites of the Daldyn Group of the Anabar Shield. Obtained age of magmatic crystallization for biotite–hypersthene crystalline schists and garnet amphibolites agree with position of zircons within terrestrial array. Magmatic genesis of plagiogranite neosome under granulite conditions was established for leucocratic plagiogneisses.  相似文献   

Zircons,age, and geological setting of rhyodacite–porphyry from the Bagrusha Complex (South Urals)     

V. N. Puchkov  A. A. Krasnobaev  N. D. Sergeeva  S. V. Busharina  S. P. Shokalsky 《Doklady Earth Sciences》2017,477(1):1295-1300

Before our studies, it was considered that the Bagrusha rhyolite–porphyry complex (BC) including veins and thin dykes occurring in the Kusa region among deposits presumably of the Satka and Avzyan Formations of the Lower and Middle Riphean, respectively. Based on the U–Pb SHRIMP and IDTIMS studies of zircons from rhyodacite—porphyry, we established the age of the BC formation of T₀ = 1348.6 ± 3.2 Ma for the first time. The age obtained is inconsistent with the idea on the Paleozoic age of the BC and the geological situation shown on geological maps of the region. The age (T₀ = 1348.6 ± 3.2 Ma) of rhyodacite–porphyry from the BC provides evidence for acid volcanism controlled by the Mashak (Middle Riphean) magmatic event in the region, and deposits hosting volcanic rocks of the BC cannot be younger than the base of the Middle Riphean, i.e., the Mashak Formation, which was not previously distinguished by researchers in the western part of the Kusa and Bakal–Satka regions. At the same time, it is possible that deposits hosting dykes and veins of the granite–rhyolite formation may have a Bakal (Lower Riphean) age.  相似文献