Investigation of the new cataclysmic variable 1RXS J180834.7+101041     

D. G. Yakin  V. F. Suleimanov  N. V. Borisov  V. V. Shimanskii  I. F. Bikmaev 《Astronomy Letters》2011,37(12):845-857

We present the results of our photometric and spectroscopic studies of the new eclipsing cataclysmic variable star 1RXS J180834.7+101041. Its spectrum exhibits double-peaked hydrogen and helium emission lines. The Doppler maps constructed from hydrogen lines show a nonuniform distribution of emission in the disk similar to that observed in IP Peg. This suggests that the object can be a cataclysmic variable with tidal density waves in the disk. We have determined the component masses (M _WD = 0.8 ± 0.22M _⊙ and M _RD = 0.14 ± 0.02M _⊙) and the binary inclination (i = 78° ± 1.5°) based on well-known relations between parameters for cataclysmic variable stars. We have modeled the binary light curves and showed that the model of a disk with two spots is capable of explaining the main observed features of the light curves.  相似文献   

Ejecta formation and crater development of the Mjølnir impact     

Valery SHUVALOV  Henning DYPVIK 《Meteoritics & planetary science》2004,39(3):467-479

Abstract— Crater‐ejecta correlation is an important element in the analysis of crater formation and its influence on the geological evolution. In this study, both the ejecta distribution and the internal crater development of the Jurassic/Cretaceous Mjølnir crater (40 km in diameter; located in the Barents Sea) are investigated through numerical simulations. The simulations show a highly asymmetrical ejecta distribution, and underscore the importance of a layer of surface water in ejecta distribution. As expected, the ejecta asymmetry increases as the angle of impact decreases. The simulation also displays an uneven aerial distribution of ejecta. The generation of the central high is a crucial part of crater formation. In this study, peak generation is shown to have a skewed development, from approximately 50–90 sec after impact, when the peak reaches its maximum height of 1‐1.5 km. During this stage, the peak crest is moved about 5 km from an uprange to a downrange position, ending with a final central position which has a symmetrical appearance that contrasts with its asymmetrical development.  相似文献   

Constraints on interpretation of the Eltanin impact from numerical simulations     

Valery Shuvalov  Rainer Gersonde 《Meteoritics & planetary science》2014,49(7):1171-1185

The results of numerical simulations of the Eltanin impact are combined with the available geological data in order to reconstruct the impact dynamics and to get some constraints on the impact parameters. Numerical simulations show that the Eltanin projectile size should be less than 2 km for a 45° oblique impact and less than 1.5 km for a vertical impact. On the other hand, we demonstrate that the projectile diameter cannot be considerably smaller than 1 km; otherwise, the impact‐induced water flow cannot transport eroded sediments across large distances. The maximum displacement approximately equals the water crater radius and rapidly decreases with increasing distances. Numerical simulations also show that ejecta deposits strongly depend on impact angle and projectile size and, therefore, cannot be used for reliable estimates of the initial projectile mass. The initial amplitudes of tsunami‐like waves are estimated. The presence of clay‐rich sediments, typical for the abyssal basins in cores PS2709 and PS2708 on the Freeden Seamounts (Bellingshausen Sea, Southern Ocean) combined with numerical data allow us to suggest a probable point of impact to the east of the seamounts. The results do not exclude the possibility that a crater in the ocean bottom may exist, but such a structure has not been found yet.  相似文献   

Khatyrka,a new CV3 find from the Koryak Mountains,Eastern Russia     

Glenn J. MacPherson  Christopher L. Andronicos  Luca Bindi  Vadim V. Distler  Michael P. Eddy  John M. Eiler  Yunbin Guan  Lincoln S. Hollister  Alexander Kostin  Valery Kryachko  William M. Steinhardt  Marina Yudovskaya  Paul J. Steinhardt 《Meteoritics & planetary science》2013,48(8):1499-1514

A new meteorite find, named Khatyrka, was recovered from eastern Siberia as a result of a search for naturally occurring quasicrystals. The meteorite occurs as clastic grains within postglacial clay‐rich layers along the banks of a small stream in the Koryak Mountains, Chukotka Autonomous Okrug of far eastern Russia. Some of the grains are clearly chondritic and contain Type IA porphyritic olivine chondrules enclosed in matrices that have the characteristic platy olivine texture, matrix olivine composition, and mineralogy (olivine, pentlandite, nickel‐rich iron‐nickel metal, nepheline, and calcic pyroxene [diopside‐hedenbergite solid solution]) of oxidized‐subgroup CV3 chondrites. A few grains are fine‐grained spinel‐rich calcium‐aluminum‐rich inclusions with mineral oxygen isotopic compositions again typical of such objects in CV3 chondrites. The chondritic and CAI grains contain small fragments of metallic copper‐aluminum‐iron alloys that include the quasicrystalline phase icosahedrite. One grain is an achondritic intergrowth of Cu‐Al metal alloys and forsteritic olivine ± diopsidic pyroxene, both of which have meteoritic (CV3‐like) oxygen isotopic compositions. Finally, some grains consist almost entirely of metallic alloys of aluminum + copper ± iron. The Cu‐Al‐Fe metal alloys and the alloy‐bearing achondrite clast are interpreted to be an accretionary component of what otherwise is a fairly normal CV3 (oxidized) chondrite. This association of CV3 chondritic grains with metallic copper‐aluminum alloys makes Khatyrka a unique meteorite, perhaps best described as a complex CV3 (ox) breccia.  相似文献   

Lacustrine sediments and lichen transplants: two contrasting and complimentary environmental archives of natural and anthropogenic lead in the South Urals, Russia     

Baruch Spiro  Valery Udachin  Ben J. Williamson  O. William Purvis  Svetlana G. Tessalina  Dominik J. Weiss 《Aquatic Sciences - Research Across Boundaries》2013,75(2):185-198

Lead (Pb) concentrations and isotope ratios of two different geochemical archives are compared; lake sediment cores and lichens (Hypogymnia physodes, naturally growing and transplanted) from a ca. 80 km-long transect centred on the Cu smelter and former mining town of Karabash, Ural Mountains, Russia. Lead concentrations in sediment cores from 10 lakes were generally low near their base and show an abrupt increase in their upper portions interpreted to coincide with the onset of large-scale smelting operations in 1910. Lead isotope ratios derived from ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb of the bottom layers differed significantly from those of the top. The top sediments have isotope ratios that show distinct end members, one of which was the stack dust from the Karabash smelter, which is similar to the Pb derived from ores from Sibay, a major mine in the Urals. The composition of the bottom sediment layers generally fall slightly off a mixing line between the top sediments and average Earth’s upper crust. Lichens transplanted from a reference site, as well as naturally growing lichens, sampled from southwest of the smelter have isotope ratios similar to those of the stack dust. Lichens to the northeast contained Pb from the smelter, but are increasingly influenced by other sources probably leaded petrol and local soils, and a signature derived from a source enriched in ²⁰⁷Pb. Vegetables collected from local kitchen gardens contained Pb from an additional atmospheric source, possibly coal. Our work confirms that: (1) Pb isotopes in lake sediments provide a long-term record of inputs and allows the characterisation of natural and anthropogenic sources; (2) Pb isotopes in lichens provide a short-term record of local and long-range atmospheric deposition at high spatial resolution and short time scales as they replace their Pb content within a few months; (3) determination of all four stable Pb isotopes is necessary for the identification of the sources of Pb and is extremely sensitive for discerning minor source signatures, even in an area with a dominant source such as a smelter. Particularly significant for the Karabash area is that ore-smelter-derived airborne Pb is a major component in the lake sediments and lichens but its contribution reaches insignificant levels ca. 40 km from the smelter.  相似文献   

Geographical extremes in the glacial history of northern Eurasia: post-QUEEN considerations     

Valery Astakhov 《Polar research》2008,27(2):280-288

This paper summarizes the principal results produced by the European Science Foundation's programme, Quaternary Environment of the Eurasian North (QUEEN). These results concern the distribution of late Quaternary glaciers of different ages across northern Eurasia. The pattern of glaciation is compared with the west–east climatic gradient of the continent. Of particular significance is the coincidence of the Late Weichselian ice margin with the modern 30°C difference between the July and January mean air temperatures. The difference between west and east in the annual amplitude of air temperature did not decrease during the Pleniglacial. The asymmetry of the glacial history suggests a progressive aridification of the Eurasian North, with the result that by marine isotope stage 2 significant ice volumes could only accumulate along the Atlantic seaboard. The different climatic signals of thermochrons and cryochrons of the extreme west and east of the continent are discussed. The growth of continentality eastwards restrains the applicability of pollen proxies for climatic reconstructions.  相似文献   

The evolutionary status of UX CVn     

V. V. Shimansky  N. V. Borisov  N. A. Sakhibullin  V. F. Suleimanov  M. S. Stupalov 《Astronomy Reports》2002,46(8):656-666

We have analyzed available spectroscopic and photometric observations of the close binary UX CVn using model atmospheres. Theoretical spectra and light curves were derived from models of a precataclysmic variable and a close binary consisting of degenerate stars. We have used the 6-m telescope of the Special Astrophysical Observatory to obtain ten moderate-resolution spectra at three orbital phases. Our analysis of the radial-velocity curve shows that the orbital period of the system has been stable over 40 yrs, and the variations of the intensities of lines of various elements at different phases and radial velocities indicates an absence of the reflection effect. As a result, we have classified UX CVn as a detached close binary consisting of a hot, low-luminosity sub-dwarf primary and a white-dwarf secondary.  相似文献   

Comment on “A mechanistic model for interpretation of hydrogen and oxygen isotope ratios in tree-ring cellulose,” by J. S. Roden, G. Lin, and J. R. Ehleringer (2000) Geochim. Cosmochim. Acta, 64, 21-35     

Valery J Terwilliger∗ 《Geochimica et cosmochimica acta》2002,66(4):729-731

  相似文献   

Geodetic observations of ice flow velocities over the southern part of subglacial Lake Vostok, Antarctica, and their glaciological implications   总被引：1，自引：0，他引：1  

Jens Wendt  Reinhard Dietrich  Mathias Fritsche  Anja Wendt  Alexander Yuskevich  rey Kokhanov  Anton Senatorov  Valery Lukin  Kazuo Shibuya  Koichiro Doi 《Geophysical Journal International》2006,166(3):991-998

In the austral summer seasons 2001/02 and 2002/03, Global Positioning System (GPS) data were collected in the vicinity of Vostok Station to determine ice flow velocities over Lake Vostok. Ten GPS sites are located within a radius of 30 km around Vostok Station on floating ice as well as on grounded ice to the east and to the west of the lake. Additionally, a local deformation network around the ice core drilling site 5G-1 was installed.
The derived ice flow velocity for Vostok Station is  2.00 m a⁻¹± 0.01 m a⁻¹  . Along the flowline of Vostok Station an extension rate of about 10⁻⁵ a⁻¹ (equivalent to 1 cm km⁻¹ a⁻¹) was determined. This significant velocity gradient results in a new estimate of 28 700 years for the transit time of an ice particle along the Vostok flowline from the bedrock ridge in the southwest of the lake to the eastern shoreline. With these lower velocities compared to earlier studies and, hence, larger transit times the basal accretion rate is estimated to be 4 mm a⁻¹ along a portion of the Vostok flowline. An assessment of the local accretion rate at Vostok Station using the observed geodetic quantities yields an accretion rate in the same order of magnitude. Furthermore, the comparison of our geodetic observations with results inferred from ice-penetrating radar data indicates that the ice flow may not have changed significantly for several thousand years.  相似文献   

The amphipod Orchomenella pinguis – A potential bioindicator for contamination in the Arctic     

Lis Bach  Valery E. Forbes  Ingela Dahllf 《Marine pollution bulletin》2009,58(11):1664-1670

Indigenous organisms can be used as bioindicators for effects of contaminants, but no such bioindicator has been established for Arctic areas. Orchomenella pinguis is a benthic amphipod, ubiquitous in the Arctic and can be found in high numbers. We collected O. pinguis at sites with different contamination levels. Population characteristics (body length distribution, average dry weight and amphipod organic content) were related to sediment contaminant concentrations, in order to identify suitable endpoints for using this species as a bioindicator. We show that O. pinguis was prevalent in both clean and contaminated areas, easy to sample and that its population characteristics could be linked to both contamination and sediment organic content. We suggest that O. pinguis is a suitable bioindicator for the Arctic, but that endpoints such as reproductive effects and phenotypic and genotypic responses are needed together with population characteristics to assess impacts of contamination.  相似文献