Three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr with an accretor wind

We present three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr taking into account explicitly radiative cooling and the stellar wind of the accretor. Our computations show that flow forces wind out from the orbital plane, where an accretion disk with a radius of 0.4–0.5 and a height of about 0.15–0.17 (in units of orbital separation) is formed. Gas motions directed upward from the orbital plane are initiated in the region of interaction of the flow from L₁ and the accretor wind (x = 0.91, y = ?0.17); i.e., a jetlike structure forms. This structure has the shape of a gas pillar above the orbital plane, where gas moves with the velocity of stellar wind. The number density of the gas in this structure is about 10¹⁴ cm^?3, and its temperature is 20 000–45 000 K. At heights of about 0.15–0.20 above the orbital plane, in the region between the jetlike structure and the disk, two spiral shocks form. It is possible that the emission lines observed in the spectrum of β Lyr binary originate in this region.     

Formation of the accretion disk in the SS 433 system with explicit radiative cooling,convective heat conduction,and radiation pressure

The paper continues three-dimensional hydrodynamical computations of the formation of an accretion disk in the SS 433 system, taking into account radiative cooling explicitly, convective thermal conductivity, and radiation pressure. The computational results show that the powerful, broad flow forms an optically thick accretion disk with a gas density of 10¹²–10¹⁴ cm^?3, a temperature of 15000–35 000 K, a radius of about 0.3, and a height of 0.2–0.3 (in units of the component separation). Spiral shocks form in the disk, and a narrow conelike cavity (tunnel) forms at the center. In this tunnel, gas is accelerated to relativistic speeds, leaving the system in the form of narrow jets.     

Stream formation in W Serpentis-type binaries

By the method proposed by Nazarenko (1993) and using observational data obtained by different authors, the physical conditions in the stream in the neighbourhood of the inner Lagrangian point L₁ were calculated for three interacting binary systems of W Ser-type: β Lyr, V367 Cyg, RY Sct. It is shown, that as a result of the evolutional expansion of the mass losing component the deep layers of its atmosphere reach the neighbourhood of the first Lagrangian point L₁ and a stream of axial symmetric shape is formed. Its radius is comparable to the dimension of the mass losing component. The rate of the mass transfer increases up to 10⁻⁵ M_⊙/yr. The calculated parameters of the stream in the neighbourhood of the point L₁ explain the main observational properties of the investigated systems (existence of extended circumstellar matter with a developed structure, high mass transfer rate).     

Three three-dipole stars

We analyzed magnetic-field structures of three three-dipole magnetic stars HD 18078, HD 37776, and HD 149438. The fact that the model and observed phase dependences B _e (Φ) and B _s (Φ) for HD 18078 computed with the same parameters of the dipoles agree with each other shows conclusively that global magnetic structures are formed by dipole structures. Magnetic poles show up conspicuously on Mercator maps of the distribution of magnetic field, the field strength there is maximal and equal to B _p = 3577, 10 700, and 275Gin the three stars mentioned above.Dipolemodelsmake it possible to analyze magnetic-field structure inside stars.     

Modeling Technogenous Contamination of the Near-Earth Space

In analyzing the technogenous contamination of the near-earth space (NES), the following issues have usually been considered: the estimation of the current level of NES contamination by objects of various size; the modeling of technogenous contamination evolution; the estimation of the probability of spacecraft collisions with space objects (SOs) of various size and the possible implications of hazardous collisions; the determination of characteristics of the flux of SOs of various size through the observation zones of ground-based and onboard means of measurement. The main difficulty in solving the aforementioned problems lies in the deficiency of the experimental data. The available measurement information was obtained in relatively small domains of multidimensional space: the altitude of a point–the latitude of a point–the SO size–the time. As a consequence, additional (a priori) information is invoked for determining the technogenous contamination characteristics at various points of the region mentioned above. The efficient use of experimental data and a priori information constitutes the basic problem of space debris modeling. This paper briefly outlines the data on three space debris (SD) models: ORDEM2000 (Orbital Debris Engineering Model, 2000), MASTER'99 (Meteoroid and Space Debris Terrestrial Environment Reference Model, 2000) and SDPA (Nazarenko, 1997, 2000; Nazarenko and Menshikov, 2001). The features of modeling techniques and the comparative characteristics of technogenous contamination are discussed in the paper.     

Three-dimensional hydrodynamical modeling of the formation of the accretion disk in the SS 433 binary system

Three-dimensional hydrodynamical modeling of the formation of the accretion disk in the SS 433 binary system is carried out with various types of cooling and numerical grids. These computations show that a thick accretion disk with a height of 0.25–0.30 (in units of the component separation) is formed around the compact object, from a flow with a large radius (0.2–0.3 in the same units) that forms in the vicinity of the inner Lagrangian point. This disk has the form of a flattened torus. The number of orbits of a particle of gas in the disk is 100–150, testifying to a minimal influence of numerical viscosity in these computations. The computations also show that the stream flowing from L₁ is nearly conservative, and spirals in the disk are not formed due to the influence of the donor gravitation.     

Two-and three-dimensional hydrodynamical simulations of mass transfer in semidetached binaries with explicit radiative cooling and self-absorption in their gaseous envelopes

We have modeled the mass transfer in three Algol-type binaries using two-and three-dimensional numerical hydrodynamical techniques. Radiative cooling and absorption in the envelopes surrounding the components of the close binaries are explicitly taken into account. The resulting envelope temperatures are consistent with those observed. We derived these temperatures by considering the energy balance in the moving gas, including heating due to the numerical viscosity that is inherent to the simulations and radiative cooling. The radiative cooling was calculated assuming an optically thin plasma in a state of ionization balance. Taking into account both of these processes yielded temperatures of 4000–30 000 K in the disk around the accreting primary and in the common envelope surrounding the close binary. Our computations also indicate that the envelope morphology is not sensitive to the radiative-cooling model used.     

Ecotone system of the southeastern coast of the Tsimlyansk Reservoir

The results of multidisciplinary environmental field studies aimed to elucidate the forms of influence of the Tsimlyansk Reservoir onto coastal ecosystems are presented. The ecotone analysis of the ecosystem structure of the reservoir coast is proposed as an approach to the analysis of the collected data. A brief characteristic of a version of a geographic information system based on field and remote-sensing data is given. A relationship is shown to exist between the reservoir level regime according to 10-year data and the transformation of vegetation cover on the coast against the background of minor changes in soils for the 50-year period of reservoir existence.     

Application of the method for optimum filtering of measurements for determination and prediction of spacecraft orbits

The article covers the outcome of the method for optimal filtering of measurements developed by the author and aimed at the determination of the time and place of reentry of the Phobos-Grunt spacecraft. So-called two-line elements (TLE) of the orbit of the American Space Surveillance System are used as measurements.