Parameters of V404 Cyg—A black-hole binary

We present the results of spectroscopic observations of the X-ray binary V404 Cyg obtained on the 6-m telescope of the Special Astrophysical Observatory in 2001–2002. We have used a statistical approach to interpret the radial-velocity curve of V404 Cyg. We derived the dependence of the mass of the X-ray emitting component m_x on the mass of the optical component m_v via an analysis of the radial-velocity curve based on profiles of the CaI 6439.075 Å absorption line synthesized in a Roche model. Using the orbital inclination estimated from the ellipticity of the optical component, i=54°–64°, and the component-mass ratio q=m_x/m_v=16.7 found from the rotational broadening of the spectral lines, we obtain m _s =10.65±1.95M_⊙ for the mass of the black hole.     

Radiogeochemical studies of the features of radionuclide distribution at the sites of dumping of radioactive wastes of the Novaya Zemlya Archipelago

This paper presents the results of the studies performed from aboard the R/V Akademik Boris Petrov of the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, in 2002–2004 aimed at surveying the sites of dumping of potentially dangerous objects in Stepovoy, Abrosimov, and Tsivol’ka bays of the Kara Sea. These studies coupled the instrumental facilities of acoustic survey with the visual examination of the objects recovered and also included sampling of the bottom sediments and near-bottom water in the vicinity of the objects and away from them. Subsequently, the samples collected were analyzed using direct gamma spectrometry and radiochemical concentrating selected radionuclides. This allowed us to obtain a statistically reliable database on the specific concentrations of radionuclides (cesium, strontium, cobalt, and plutonium) in the water column and in the bottom sediments. In selected parts of Stepovoy and Abrosimov bays, at the sites where containers were located, local areas with contaminated bottom sediments were registered in the immediate vicinity of the objects, in which significant concentrations of Cs-137 were detected. We also carried out experiments with the samples of the collected bottom sediments on the determination of the kinetic parameters of sorption in the sediment-solution system using the method of radioactive indicators. Taking into account the hydrological conditions, the results obtained allow one to explain particular features of radioactivity distribution in selected aquatic areas. Based on a comparison between the results of the studies performed in 1992–1994 and 2002–2004, we estimated the dynamics of the changes in the mean level of specific concentrations of radionuclides in the regions of the location of sunken objects in shallow-water bays of the Novaya Zemlya Archipelago. The registration of elevated concentrations of corrosive elements in the surface layers of the bottom sediments in these zones suggests a necessity of a multidisciplinary study consisting of regular repeated measurements at reference points in different areas aimed at before-the-fact prevention of possible leakages of radioactive substances from the sunken objects, which might result in a significant contamination of the environment. Original Russian Text ? O.V. Stepanets, L.A. Kodina, A.N. Ligaev, A.P. Borisov. G.Yu. Solov’eva, 2006, published in Geokhimiya, 2006, No. 12, pp. 1315–1324.     

Geochemical structure of base-metal filling veins and parameters of hydrothermal ore formation

The aim of this study was to determine at which parameters hydrothermal systems generate rich veins with bulk sphalerite contents of 30% and local concentrations in vein cross sections up to 60–70% and more. Such contents were found in the vein bodies of the Dzhimi deposit in the Sadon ore district, North Osetiya. For this purpose, we examined the thermodynamic models of the formation of base-metal filling veins. Ore-bearing fluids are formed in the root part of the hydrothermal system by the interaction of barren solutions with the host rocks (granites), which contain background contents of ore elements. The thermodynamic simulations were conducted for the system H-O-K-Na-Ca-Mg-Al-Si-Fe-C-Cl-S-Zn-Pb-Cu, which is described by 54 minerals of constant and variable composition and 78 aqueous species. The calculations for the mobilization zone were carried out for the temperature range of 360–440°C (through 10°C) and pressures of 600–1200 bar (with a 100 bar step). At each of the indicated temperature and pressure values, 100 waves (portions) of primary barren solution were subsequently passed through the granites. More than 20 complete models of the formation of filling veins (each model involving from 1000 to 1300 calculations) were constructed for individual T-P points in the mobilization zone, which was modeled by a sequence of multiwave step flowing reactors with a step of 10°C from 350–420 to 100°C at a constant pressure within the range of 600–1100 bar. We studied the effect of different background contents of Zn and Pb in granites on the efficiency of mobilization and ore formation and compared the relations in the naturally occurring distribution of ore elements along the continuous cross sections through Pb-Zb veins with the results of thermodynamic simulation. It was established that ore bodies with indicated bulk and local cross sectional contents of sphalerite could be formed in a narrow range of conditions in the mobilization zone (410–440°C and 900–1200 bar) and elevated background contents of Zn (more than 0.007 wt %) in the host granite. The maximum sphalerite contents (bulk and local in vein cross sections) are achieved updip the model veins within the temperature range of 150–200°C. Original Russian Text ? M.V. Borisov, D.A. Bychkov, Yu.V. Shvarov, 2006, published in Geokhimiya, 2006, No. 11, pp. 1218–1239.     

Experimental study of the effect of SiO2 on Ni solubility in silicate melts

The solubility of Ni in silicate melts with variable SiO₂ content was studied at a total pressure of 1 atm within a wide range of temperature and oxygen fugacity. The maximum solubility of Ni (minimum activity coefficient of NiO) was observed in melts with ～55–57 wt % SiO₂, regardless of temperature and oxygen fugacity. Melts beyond this range showed significantly lower Ni solubility and, correspondingly, higher NiO activity coefficients. The analysis of our results and literature data led us to the conclusion that the NBO/T (number of nonbridging oxygen atoms per tetrahedrally coordinated atom) is inadequate to describe the effect of melt composition on Ni solubility.     

Spectropolarimetric Observations of the Unique White Dwarf GD 356 on the 6-m BTA

The results of spectropolarimetric observations of a unique magnetic white dwarf with emission lines, GD 356, on the 6-m BTA are presented. The star's magnetic field is estimated and it is shown not to rotate over times of 5 yr. Allowance for magnetic deformation of the star's surface, resulting an a nonuniform temperature distribution over its surface, showed that in the region of the magnetic poles the conditions may be satisfied for a radiative diskon in the form of a plasma jet, originating from the action of cyclotron radiation pressure. It is shown that the effect of nonuniformity of the surface temperature distribution of the white dwarf can produce the observed broad-band and resonance polarization of the stellar emission.     

Spectral types of four binaries based on photometric observations

We present results of photometric and spectroscopic observations of four close binaries with subdwarf B components: PG 0918+029, PG 1000+408, PG 1116+301, PG 0001+275. We discovered that PG 1000+408 is a close binary, with the most probable orbital period being P _orb = 1.041145 day. Based on a comparison of the observed light curves at selected orbital phases and theoretical predictions for their variations, all the systems are classified as doubly degenerate binaries with low-luminosity white-dwarf secondaries.     

V1327 Aquilae: A New RR Lyrae variable with an extremely high radial velocity

We have carried out photometry and spectroscopy of the star V1327 Aql (R = 16 ^m ) as part of our program of observations of poorly studied cataclysmic variables using the 1.5-m optical Russian—Turkish telescope (RTT-150, Turkey) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. After analyzing our photometry, we have re-classified the variable as an RR Lyrae star. Our BV R photometry during 10 nights reveals brightness variations with the period 12^h49^m, with the B, V, and R amplitudes being 1.36 ^m , 1.13 ^m , and 1.11 ^m , respectively. We derived the first estimates of the star’s atmospheric parameters from our moderate-resolution spectra: T _eff = 6280 K, log g = 3.3, [M/H] = ?1.05. The extremely high radial velocity of the star’s motion (V _R = ?470 km/s) and the star’s large distances to the Galactic center (13.1 kpc) and disk (4.2 kpc) testify to a probable extragalactic origin of this object.     

Structure of the earth''s crust on the territory of the U.S.S.R.

The compilation of statistical data for 269 seismic crustal sections (total length: 81,000 km) which are available in the U.S.S.R. has shown that the preliminary conclusions drawn on relations between the elevation of the surface relief and Bouguer anomalies on one hand and crustal thickness (depth to the M-discontinuity) on the other hand are not fulfilled for the continental part of the U.S.S.R. The level of isostatic compensation has been found to be much deeper than the base of the earth's crust due to density inhomogeneities of the crust and upper mantle down to a depth of 150 km.

The results of seismic investigations have revealed a great diversity of relations between shallow geological and deep crustal structures:

Changes in the relief of the M-discontinuity have been found within the ancient platforms which are conformable with the Precambrian structures and which can exceed 20 km. In the North Caspian syneclise, extended areas devoid of the “granitic” layer have been discovered for the first time in continents. The crust was found to be thicker in the syneclises and anteclises of the Turanian EpiHercynian plate. In the West Siberian platforms these relations are reversed to a great extent.

Substantial differences in crustal structure and thickness were found in the crust of the Palaeo zoides and Mesozoides. Regions of substantial neotectonic activity in the Tien-Shan Palaeozoides do not greatly differ in crustal thickness if compared to the Kazakhstan Palaeozoides which were little active in Cenozoic time. The same is true for the South Siberian Palaeozoides.

The Alpides of the southern areas in the U.S.S.R. display a sharply differing surface relief and a strongly varying crustal structure. Mountains with roots (Greater Caucasus, Crimea) and without roots (Kopet-Dagh, Lesser Caucasus) were found there.

The Cenozoides of the Far East are characterized by a rugged topography of the M-discontinuity, a thinner crust and a less-pronounced “granitic” layer. A relatively small thickness of the crust was discovered in the Baikal rift zone.

The effective thickness of the magnetized domains of the crust as well as other calculations show that the temperature at the depth of the M-discontinuity (i.e., at depths of 40–50 km) is not higher than 300–400° C for most parts of the U.S.S.R.     

Experimental study of the influence of SiO<Subscript>2</Subscript> on the solubility of cobalt and iron in silicate melts

The solubility of cobalt and iron in silicate melts with variable SiO₂ content was experimentally determined under controlled oxygen fugacity. It was shown that, independent of temperature and oxygen fugacity, the solubility of the two metals reaches a maximum (minimum of CoO and FeO activity coefficients) in melts of intermediate compositions. The analysis of available published data demonstrated that the γ_MeO values of at least four metals (Ni, Co, Fe, and Cr) dissolving in melts as divalent oxides show a minimum in melts with \(X_{SiO_2 } \) ≈ 57 ± 2 mol %. The position of the minimum is essentially independent of the element, melt temperature, and oxide concentration (from a few ppm to 13 wt%). The extremes of iron solubility (γ_FeO) in Fe-rich MgO-free melts may shift toward significantly lower \(X_{SiO_2 } \) values, although this inference requires additional experimental verification. Using a numerical example, some problems were discussed in the use of experimental data obtained in different laboratories for the development of a general model for the γ_MeO dependence on melt composition.