Search

The distribution of visual interstellar extinction $A_V$ has been mapped in selected areas over the Northern sky, using available LAMOST DR5 and Gaia DR2/EDR3 data. $A_V$ was modelled as a barometric function of galactic latitude and distance. The function parameters were then approximated by spherical harmonics. The resulting analytical tridimensional model of the interstellar extinction can be used to predict $A_V$ values for stars with known parallaxes, as well as the total Galactic extinction in a given location in the sky., Comment: 18 pages, 33 figures, accepted by EPJ

Учет межзвездного поглощения - необходимый этап в процессе параметризации звезд по многоцветной фотометрии. Мы анализируем опубликованные законы межзвездного поглощения и обсуждаем возможность оценки величины межзвездного поглощения для фотометрических полос современных больших обзоров. Taking into account interstellar extinction is the necessary procedure in the process of parameterization of stars from multicolor photometry. We analyze published interstellar extinction laws and discuss the possibility of assessing the interstellar extinction in photometric bands of modern large surveys.

Multi-wavelength characterization of astrophysical objects by means of cross-matching of modern large sky surveys is a powerful tool intensively used for classification, parameterization and studies of various classes of sources. The objects detected in many or all surveys under study represent convenient material for the research, however, objects that are found in only one of the surveys, and absent in all others, should also attract close attention. Our goal is to identify and study objects apparent in only a single wave band, and invisible in the others. It is still a relatively poorly investigated field and may lead to the detection of a new unique (or transient) class of objects. Here we explore the possibility of detecting of objects with a significant UV excess in their spectra by cross-matching of the GALEX all-sky catalogue with several other surveys in different wavelength ranges and analyzing the ones visible in GALEX only (ultraviolet luminous objects). We describe the methodology for such investigation, explain the selection of surveys for this study, and show initial results based on the search in several small sky areas. The ultraviolet luminous objects should reside in the Milky Way Galaxy and must be either very hot massive stars in the main sequence stage of their evolution, or isolated old neutron stars, slowly accreting interstellar matter. Our results will be used as an input for a larger-scale investigation.

We suggest a method allowing to investigate existence and the measure of proximity between the stationary solutions to continuous and discontinuous neural fields with microstructure. The present part involves results on proximity of the stationary solutions to specific homogenized neural field equations with continuous and discontinuous activation functions. The results of numerical investigation of radially symmetric stationary solutions (bumps) to the neural field with a discontinuous activation function and a given microstructure are presented.

Analytical methods are used to study nonlinear deformation of a plane with an elliptical inclusion. The elastic properties of a material of the plane and inclusion are described with a semi-linear material. The external load is constant nominal (Piola) stresses at infinity. At the inclusion boundary, the conditions of the continuity for stresses and displacements are satisfied. Semi-linear material belongs to the class of harmonic, the methods of the theory of functions of a complex variable are applicable to solving nonlinear plane problems. Stresses and displacements are expressed in terms of two analytical functions of a complex variable, determined by the boundary conditions on the inclusion contour. It is assumed that the stress state of an inclusion is uniform (the tensor of nominal stresses is constant). This hypothesis made it possible to reduce the difficult nonlinear problem of conjugation of two elastic bodies to the solution of two more simpler problems for a plane with an elliptical hole. The validity of this hypothesis is justified by the fact that the constructed solution exactly satisfies all the equations and boundary conditions of the problem. The same hypothesis was used earlier by other authors to solve linear and nonlinear problems of an elliptical inclusion. In the article, a comparative analysis of the stresses and strains is carried out for two models of harmonic materials — semi-linear and John’s. Various variants of values of elasticity parameters of the inclusion and matrix have been considered.

The parameterization of stars is a well-known problem and used for various purposes in astronomy. We have shown that multicolor photometric data from large modern surveys can be used for parameterization of stars. With sufficiently good quality photometry, one may compute a 3D extinction map by comparing catalogued multicolor photometry with photometry derived from the secondary estimators such as the distance modulus and the interstellar extinction law with suitable calibration tables for absolute magnitudes with reasonable spectral types, extinctions and distances.

В данной работе предпринимается попытка обнаружить среди визуальных двойных звезд системы с компонентами разного возраста. Для этого сравниваются спектральные классы компонентов, а также их массы, оцененные из этой спектральной классификации. Применение этого простого метода к Каталогу орбитальных двойных звезд ORB6 позволило обнаружить тринадцать систем, у которых менее массивный компонент выглядит более проэволюционировавшим (т.е., два компонента, по-видимому, имеют разный возраст). Для уточнения результатов требуются дальнейшие исследования. The aim of this study is to find non-coeval pairs among visual binaries. For indication of non-coevality we compare spectral classes and masses of the components, estimated from the spectral classification. Applying this simple method to the Catalogue of orbital binaries ORB6, we found thirteen systems where less massive component is more evolved, and, consequently, the components are probably non-coeval. To prove non-coevality one needs a detailed investigation of the candidates.

Semidetached eclipsing systems provide a unique opportunity to derive the basic properties of interacting binaries. The goal of this work is to collect and to make use of data on semidetached systems with available light and radial velocity curve solutions. I have compiled the most comprehensive list to date, of 119 semidetached double-lined eclipsing binaries, containing the orbital parameters and physical parameters of the components. I consider the classification of semidetached binaries and discuss gaps between various classes in the Hertzspung–Russell diagram. I list systems with component parameters that are inverted and briefly discuss their evolutionary state.

Large-scale instability of gravitating systems plays a key role in collisionless relaxation and in reaching a quasi-stationary state at the early stage of evolution. Advanced high-resolution methods and permanently increasing performance of computational systems allow this phenomenon to be studied by means of computer simulations at a new level. In this paper, an approach to verification and validation of computer codes implementing high-resolution methods is proposed. The approach is based on comparisons of the simulation results with exact non-stationary solutions of the Vlasov–Poisson equations. The evolution of the gravitating layer model is considered as an example of implementation of this approach. A one-parameter family of exact models of a non-stationary gravitating layer is described, and their stability to large-scale disturbances in the linear approximation is analytically studied. Non-linear instability development is computed with the use of the fifth-order conservative semi-Lagrangian WENO scheme.

PURPOSE: The purpose of this study was to evaluate the potential skin dose toxicity contribution of spiralling contaminant electrons (SCE) generated in the air in an MR-linac with a 0.35 or 1.5 T magnetic field using the EGSnrc Monte Carlo (MC) code. Comparisons to experimental results at 1.5 T are also performed. METHODS: An Elekta generated phase space file for the Unity MR-linac is used in conjunction with the EGSnrc enhanced electric and magnetic field transport macros to simulate surface dose profiles and depth-dose curves in panels located 5 cm away from the beam edge and positioned either parallel or perpendicular to the magnetic field. Electrons generated in the air will spiral along the magnetic field lines, and though surface doses within the field will be reduced, the electrons can contribute to out-of-field surface doses. RESULTS: Surface dose profiles showed good agreement with experimental findings and the maximum simulated doses at surfaces perpendicular to the magnetic field were 3.77 ± 0.01% and 3.55 ± 0.01% for 1.5 and 0.35 T. These results are expressed as a percentage of the maximum dose to water delivered by the photon beam. The surface dose variations in the out-of-field region converge to the 0 T doses within the first 0.5 cm of material. An asymmetry in the dose distribution in surfaces positioned on either side of the photon beam and aligned parallel to the magnetic field is determined to be due to the magnetic field directing electrons deeper into, or localizing them to the surface of, the measurement panel. CONCLUSIONS: These results confirm the SCE dose contribution in surfaces perpendicular to the magnetic field and show these doses to be of the order of a few percentage of the maximum dose to water of the beam. Good agreement in the dose profiles is seen in comparisons between the MC simulations and experimental work. The effect is apparent in 0.35 and 1.5 T magnetic fields and dissipates within the first few millimeters of material. It should be noted that only SCEs from beam anteriorly incident on the patient will influence the patient surface dose, and the use of beams incident over different angles will reduce the dose to any particular patient surface.

We present an analytical review of the current state of the problems of stellar astronomy. We report the results obtained by Russian astronomers by 2017.We show that the studies conducted in Russia cover all major fields of stellar astronomy, use modern observational methods and data analysis techniques, and meet high scientific standards.

By analyzing the patterns of flexural extinction contours present on the electron-microscopic images of nanothin (~80 nm) spatial dissipative structures (SDSs) of hexagonal selenium, i.e., nanothin crystals with elastic rotational curvature of the lattice around [001], the processes of formation of torn interblock boundaries in these structures are investigated. The effect of changing the disorientation-vector sign along the torn interblock torsion boundaries is observed. A model of formation of interblock torsion boundaries is developed for nanothin selenium SDSs, the lattice of which undergoes an elastic rotational curvature around [001].

The symmetry of direct and reciprocal lattices and the symmetry of bend contours present in the electron microscopy images of nanothin crystals with elastic rotational distortion of the lattice are examined using the example of nanothin selenium crystals.

A recently observed bump in the cosmic ray (CR) spectrum from 0.3--30 TV is likely caused by a stellar bow shock that reaccelerates \emph{preexisting} CRs, which further propagate to the Sun along the magnetic field lines. Along their way, these particles generate an Iroshnikov-Kraichnan (I-K) turbulence that controls their propagation and sustains the bump. {\it Ad hoc} fitting of the bump shape requires six adjustable parameters. Our model requires none, merely depending on \emph{three physical unknowns that we constrain using the fit.} These are the shock Mach number, $M$, its size, $l_{\perp}$, and the distance to it, $\zeta_{\text{obs}}$. Altogether, they define the bump rigidity $R_{0}$. With $M$$\approx$1.5--1.6 and $R_{0}$$\approx$4.4 TV, the model fits the data with $\approx$$0.08\%$ accuracy. The fit critically requires the I-K spectrum predicted by the model and rules out the alternatives. These fit's attributes make an accidental agreement highly unlikely. In turn, $R_{0}$ and $M$ derived from the fit impose the distance-size %($\zeta_{{\rm obs}}$$-$$l_{\perp}$) relation on the shock: $\zeta_{{\rm obs}}$(pc)$\sim$$10^{2}\sqrt{l_{\perp}(\text{pc})}$. For sufficiently large bow shocks, $l_{\perp}$$=$$10^{-3}$$-$$10^{-2}$ pc, we find the distance of $\zeta_{{\rm obs}}$$=$3--10 pc. Three promising stars in this range are: Scholz's Star at 6.8 pc, Epsilon Indi at 3.6 pc, and Epsilon Eridani at 3.2 pc. Based on their current positions and velocities, we propose that Epsilon Indi and Epsilon Eridani can produce the observed spectral bump. Moreover, Epsilon Eridani's position is only $\sim$$6.7^{\circ}$ off of the magnetic field direction in the solar neighborhood, which also changes the CR arrival direction distribution. Given the proximity of these stars, the bump appearance may change in a relatively short time., Comment: 25 pages, 8 figures, pdflatex, to appear in ApJ

We model cortical travelling waves by radially symmetric solutions to planar neural field equations with periodic spatial heterogeneity, which capture e.g. the microstructure observed in the primary visual cortex. We investigate the so-called bump-solutions that correspond to generation of local excitation in the brain tissue and an early stage of radially symmetric spread of cortical waves. We study how the neural medium heterogeneity and other biophysical parameters such as neuron activation threshold, the lengths and the strengths of neuronal connections affect cortical waves mathematically represented in terms of radially symmetric solutions to neural field equations with microstructure.

Numerical simulations of particle acceleration in magnetized turbulence have recently observed powerlaw spectra where pile-up distributions are rather expected. We interpret this as evidence for particle segregation based on acceleration rate, which is likely related to a non-trivial dependence of the efficacy of acceleration on phase space variables other than the momentum. We describe the corresponding transport in momentum space using continuous-time random walks, in which the time between two consecutive momentum jumps becomes a random variable. We show that powerlaws indeed emerge when the experimental (simulation) timescale does not encompass the full extent of the distribution of waiting times. We provide analytical solutions, which reproduce dedicated numerical Monte Carlo realizations of the stochastic process, as well as analytical approximations. Our results can be readily extrapolated for applications to astrophysical phenomenology., Comment: 12 pages, 13 figures; version to appear in MNRAS (minor edits)

In situ observations of energetic particles at the Earth's bow-shock that are attainable by the satellite missions have long created the opinion that electrons are most efficiently accelerated in a quasi-perpendicular shock geometry. However, shocks that are deemed to be responsible for the production of cosmic ray electrons and their radiation from sources such as supernova remnants are much more powerful and larger than the Earth's bow-shock. Their remote observations and in situ measurements at Saturn's bow shock, suggest that electrons are accelerated very efficiently in the quasi-parallel shocks as well. In this paper we investigate the possibility that protons that are accelerated to high energies create sufficient wave turbulence, which is necessary for the electron preheating and subsequent injection into the diffusive shock acceleration in a quasi-parallel shock geometry. An additional test-particle-electron population, which is meant to be a low-density addition to the electron core-distribution on which the hybrid simulation operates, is introduced. We investigate how these electrons are energized by the hybrid electromagnetic field. The reduced spatial dimensionality allowed us to dramatically increase the number of macro-ions per numerical cell and achieve the converged results for the velocity distributions of test electrons. We discuss the electron preheating mechanisms, which can make a significant part of thermal electrons accessible to the ion-driven waves observed in hybrid simulations. We find that the precursor wave field supplied by ions has a considerable potential to preheat the electrons before they are shocked at the subshock., 9 pages, 12 figures, 1 table

The rate of inelastic nuclear interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this probability is about $$\sim 20\%$$∼20% larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller probability excess of $$\sim 4\%$$∼4%.

We describe a homogeneous catalog compilation of common proper motion stars based on Gaia DR2. A preliminary list of all pairs of stars within the radius of 100 pc around the Sun with a separation less than a parsec was compiled. Also, a subset of comoving pairs, wide binary stars, was selected. The clusters and systems with multiplicity larger than 2 were excluded from consideration. The resulting catalog contains 10358 pairs of stars. The catalog selectivity function was estimated by comparison with a set of randomly selected field stars and with a model sample obtained by population synthesis. The estimates of the star masses in the catalogued objects, both components of which belong to the main-sequence, show an excess of "twins", composed by stars with similar masses. This excess decreases with increasing separation between components. It is shown that such an effect cannot be a consequence of the selectivity function only and does not appear in the model where star formation of similar masses is not artificially preferred. The article is based on the talk presented at the conference "Astrometry yesterday, today, tomorrow" (Sternberg Astronomical Institute of the Moscow State University, October 14-16, 2019)., Comment: 18 pages, 10 figures

The main aim of this paper is to survey main trends in creating modern sources of astrometric and photometric data in astronomy. A list of existing optical, IR, and UV surveys and other surveys whose release is planned for the near future is given, together with a brief description and comparative analysis. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute,Moscow State University, October 23–25, 2017).

Most stars form in binary or multiple systems. Their evolution is defined by masses of components, orbital separation and eccentricity. In order to understand star formation and evolutionary processes, it is vital to find distributions of physical parameters of binaries. We have carried out Monte Carlo simulations in which we simulate different pairing scenarios: random pairing, primary-constrained pairing, split-core pairing, and total and primary pairing in order to get distributions of binaries over physical parameters at birth. Next, for comparison with observations, we account for stellar evolution and selection effects. Brightness, radius, temperature, and other parameters of components are assigned or calculated according to approximate relations for stars in different evolutionary stages (main-sequence stars, red giants, white dwarfs, relativistic objects). Evolutionary stage is defined as a function of system age and component masses. We compare our results with the observed IMF, binarity rate, and binary mass-ratio distributions for field visual binaries to find initial distributions and pairing scenarios that produce observed distributions.

Purpose To use EGSnrc Monte Carlo simulations for magnetic field dosimetry to determine optimal measurement orientations, calculate beam quality conversion factors for 32 cylindrical and three parallel-plate (PP) ion chambers, evaluate the beam quality and angular dependence of these factors, and examine the magnetic field effects on %dd(10)x and TPR1020. Methods Beam quality conversion factors, kQmag, and magnetic field conversion factors, kB = kQmag/kQ , are calculated as a function of chamber rotation for six cylindrical ionization chamber in either a 60 Co beam with a 0.35 T magnetic field or a 7 MV beam with a 1.5 T field, both magnetic fields are perpendicular to the photon beam. The chambers' sensitive air volumes are varied by either using the entire geometric volume or excluding the air volume associated with the first 1 mm away from the stem. The kB and kQmag factors are evaluated using four clinical photon spectra. The variation in %dd(10)x and TPR1020 as a function of magnetic field for six photon spectra are studied using DOSXYZnrc. Results When the magnetic field is perpendicular to the photon beam, orienting the chamber parallel with the magnetic field reduces the magnetic field effect on chamber response (i.e., dose to air per water dose) and variations due to the unknown sensitive volume are essentially eliminated. Calculated kB factors are within 1% of unity for the majority of cylindrical chambers, although larger kB values are associated with chambers with high-Z electrodes. PP chambers have kB corrections as large as 8.9% and have a larger angular sensitivity compared to cylindrical chambers. Values of kB for cylindrical ion chambers are independent of beam quality, except for chambers with high-Z electrodes. For %dd(10)x values between 63.3% and 73.8%, kB varies by at most (0.26 ± 0.15)% when the magnetic field is perpendicular to the photon beam and parallel to the chamber. Differences in %dd(10)x , between no magnetic field and with a 1.5 T field perpendicular to the photon beam are (0.04 ± 0.10)%, (1.89 ± 0.10)%, and (6.20 ± 0.10)% for a 60 Co, 7, and 25 MV photon beam, respectively, while TPR1020 shows less than (0.36 ± 0.10)% change. Applying the ICRU-90 recommendations for stopping powers instead of ICRU-37 is found to change kQ (and hence kB ) by less than 0.1%. Conclusions Orienting the chamber parallel to the magnetic field when the field is perpendicular to the photon beam will minimize the effect of the magnetic field on chamber response, and eliminate the problem of the unknown sensitive volume. Values of kB and kQmag can bring ion chamber dosimetry in magnetic fields in-line with the TG-51 protocol. PP chamber are sensitive to the magnetic field and variation in chamber response due to small angular changes makes them unlikely candidates for clinical reference dosimetry in magnetic fields. The stability in TPR1020, as a function of magnetic fields and beam qualities, makes it the best beam quality specifier in magnetic fields.

The algorithm of calculation of the maximum thickness of the plastic barriers, overcome spherical body with given geometric, kinematic and physical-mechanical parameters, which is based on the analysis of the deformation of a barrier and a spherical body. The technique uses the minimum parameters of the body and the obstacles presented in the relevant references. It does not require expensive mechanical and ballistic tests, based on the calculation of energy balance: energy barriers and deformation of a spherical body, the energy to move the body before the emergence of boundary stresses, leading to the destruction of barriers on the one hand and the initial kinetic energy of the spherical body with the other hand. The example used methodology (algorithm) of calculation, which showed that sufficiently accurate coincidence of the experimental and theoretical data.

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency.

In situ observations of energetic particles at the Earth's bow-shock have long created an opinion that electrons are most efficiently accelerated (injected) in a quasi-perpendicular, while protons in quasi-parallel shock geometry. Shocks that deemed responsible for the production of cosmic ray electrons and their radiation from sources such as supernova remnants are, however, much more powerful and larger. Their remote observations suggest that electrons are accelerated very efficiently in the quasi-parallel geometry. We investigate the possibility that protons accelerated to high energies create sufficient wave turbulence required for the electron injection into the diffusive shock acceleration. Numerically we do it by means of 1D hybrid simulations, in which we introduce electrons as test-particles, aiming to see how the "hybrid" fields act on the individual electrons. The reduced spatial dimensionality allowed us to dramatically increase the number of macro-ions per cell and achieve the converged results for the velocity distributions of electrons. Our simulations show, that the electron-to-proton temperature ratio is a decreasing function of the shock Mach number. Furthermore, a saturation of the temperature ratio at higher Mach numbers is noticeable. This behavior is in agreement with the electron-ion temperature ratio observed in Balmer-dominated shocks [P. Ghavamian et al., Space Science Reviews, 178, 2013].

Beam steering performance of bent silicon crystals irradiated with high-intensity and high-energy protons has been studied. In particular, crystals of the type used for collimation and extraction purposes in the Large Hadron Collider and the Super Proton Synchrotron at CERN have been irradiated at the HiRadMat CERN facility with $$2.5 \times 10^{13}$$2.5×1013 440 GeV/c protons, with a pulse length of 7.2 $$\upmu $$μs. The purpose is to study possible changes in bending angle and channeling efficiency due to thermo-mechanical stresses in case of accidental irradiation during accelerator operations. A comparison between measurements performed before and after the irradiation does not show any appreciable performance reduction in either crystal.

Creation of the Galaxy model describing formation and evolution of binary stars requires generating and testing hypotheses related to the process of formation of binary stars and distributions of their characteristics. A set of hypotheses can be generated on the basis of a number of publications that suggested the formation of binary systems. We describe the project aimed at finding initial distributions of binary stars over masses of components, mass ratios of them, semi-major axes and eccentricities of orbit, and also pairing scenarios by means of Monte-Carlo modeling of the sample of visual binaries of luminosity class V with a set of additional restrictions, so it can be considered as free of observational incompleteness effects. We present results which allow rejecting some estimated initial distributions of visual binary star parameters.

Purpose: To accurately and efficiently implement charged particle transport in a magnetic field in EGSnrc and validate the code for the use in phantom and ion chamber simulations. Methods: The effect of the magnetic field on the particle motion and position is determined using one- and three-point numerical integrations of the Lorentz force on the charged particle and is added to the condensed history calculation performed by the EGSnrc PRESTA-II algorithm. The code is tested with a Fano test adapted for the presence of magnetic fields. The code is compatible with all EGSnrc based applications, including egs++. Ion chamber calculations are compared to experimental measurements and the effect of the code on the efficiency and timing is determined. Results: Agreement with the Fano test’s theoretical value is obtained at the 0.1% level for large step-sizes and in magnetic fields as strong as 5 T. The NE2571 dose calculations achieve agreement with the experiment within 0.5% up to 1 T beyond which deviations up to 1.2% are observed. Uniform air gaps of 0.5 and 1 mm and a misalignment of the incoming photon beam with the magnetic field are found to produce variations in the normalized dose on the order of 1%. These findings necessitate a clear definition of all experimental conditions to allow for accurate Monte Carlo simulations. It is found that ion chamber simulation times are increased by only 38%, and a 10 × 10 × 6 cm3 water phantom with (3 mm)3 voxels experiences a 48% increase in simulation time as compared to the default EGSnrc with no magnetic field. Conclusions: The incorporation of the effect of the magnetic fields in EGSnrc provides the capability to calculate high accuracy ion chamber and phantom doses for the use in MRI-radiation systems. Further, the effect of apparently insignificant experimental details is found to be accentuated by the presence of the magnetic field.

Developing methods for analyzing and extracting information from modern sky surveys is a challenging task in astrophysical studies. We study possibilities of parameterizing stars and interstellar medium from multicolor photometry performed in three modern photometric surveys: GALEX, SDSS, and 2MASS. For this purpose, we have developed a method to estimate stellar radius from effective temperature and gravity with the help of evolutionary tracks and model stellar atmospheres. In accordance with the evolution rate at every point of the evolutionary track, star formation rate, and initial mass function, a weight is assigned to the resulting value of radius that allows us to estimate the radius more accurately. The method is verified for the most populated areas of the Hertzsprung-Russell diagram: main-sequence stars and red giants, and it was found to be rather precise (for main-sequence stars, the average relative error of radius and its standard deviation are 0.03% and 3.87%, respectively).

The Soviet UV space mission Astron, launched in 1983, had been operational for eight years as the largest ultraviolet space telescope during its lifetime. Astron provided a lot of observational material for various types of astrophysical objects, but unfortunately these data were not widely available and, as a result, unduly forgotten. Here we present some results of our comparison of the Astron data to the modern UV stellar data, such as the NGSL spectral library, discuss the precision and accuracy achieved with Astron, and make some conclusions on potential application areas of these data.

The Identification List of Binaries (ILB) is a star catalogue constructed to facilitate cross-referencing between different catalogues of binary stars. As of 2015, it comprises designations for approximately 120 000 double/multiple systems. ILB contains star coordinates and cross-references to the Bayer/Flemsteed, DM (BD/CD/CPD), HD, HIP, ADS, WDS, CCDM, TDSC, GCVS, SBC9, IGR (and some other X-ray catalogues), PSR designations, as well as identifications in the recently developed BSDB system. ILB eventually became a part of the BDB stellar database.

New technical capabilities have brought about the sweeping growth of the amount of data acquired by the astronomers from observations with different instruments in various parts of the electromagnetic spectrum. We consider conceptual approach to be a promising tool to efficiently deal with these data. It uses problem domain knowledge to formulate the tasks and develop problem-solving algorithms and data analysis methods in terms of domain concepts without reference to particular data sources, and thereby allows solving certain problems in general form. We demonstrate the benefits of conceptual approach by using it to solve problems related to search for secondary photometric standard candidates, determination of galaxy redshifts, creation of a binary and multiple star repository based on inhomogeneous databases, and classification of eclipsing binaries.We formulate and solve these problems over specifications of astronomical knowledge units such as photometric systems, astronomical objects, multiple stars, etc., and define them in terms of the corresponding problem domains independently of the existing data resources.

The collision of two expanding plasma flows is investigated with an emphasis on the mixing flow. The study adheres to laboratory experiments where two Ohmically exploding parallel wires launch hot plasma coronas toward each other. The interpenetration and mixing of the coronas is followed by the collision and mixing of the slowly moving phases of the melted wires. In a recent publication [M. A. Malkov and V. I. Sotnikov, Phys. Plasmas 25(10), 102108 (2018)], a stationary flow that emerges from interpenetrating coronas and plasma microinstabilities in the mixing region had been studied analytically. In this present work, using two-dimensional numerical simulations, we investigate the time evolution of the flow, compare its patterns resulting from collisions of the rarefied coronas and dense wire material, and examine the macroscopic stability of the flow. The stability of the mixing layer with respect to the so-called thin-shell instability is specifically addressed.

In this paper we identify the dominant contribution to the OFF-state distortion of an MOS transistor coming from the overlap regions applying of device-level harmonic balance simulations in a calibrated TCAD setup. Both overlap ( C gs , C gd ) and direct capacitance ( C ds ) are described with novel physics-based models that are, in conjunction with an analytical Volterra series analysis, capable of describing the harmonics. This includes the dependency on process and device design parameters such as gate oxide thickness, DC gate bias and doping profile properties in the gate overlap region. The new model is compared to the overlap models of BSIM and EKV showing superior accuracy in modeling the harmonics qualitatively and quantitatively (within 3 dBm for the second and 5 dBm for the third harmonic, respectively).

The mass-luminosity relation is a fundamental law of astrophysics. We have suggested that the currently used mass-luminosity relation is not correct for the M/M_sun > 2.7 range of mass since it was created using double-lined eclipsing binaries, where the components are synchronized and consequently change each other's evolutionary path. To exclude this effect we have started a project to study long-period massive eclipsing binaries in order to construct radial velocity curves and determine masses for the components. We outline our project and present the selected test sample together with the first HRS/SALT spectral observations and the software package, FBS (Fitting Binary Stars), that we developed for the analysis of our spectral data. As the first result we present the radial velocity curves and best-fit orbital elements for the two components of the FP Car binary system from our test sample., 12 pages, 6 figures, accepted by Research in Astronomy and Astrophysics

Methods for inferring the electron distribution function (EDF) from a probe current–voltage trace are reviewed for moderate-collisional plasma. The explicit accounting of particle collisions, modeling sheath depletion, and electron refilling processes are rarely performed when analyzing probe measurements, yet they are critical for regime validity, EDF-profile accuracy, and space potential quantification precision. The advantages, limitations, and utilization of large-area wall probes in moderate-collisional plasma, capable of highly resolved indications of energetic electrons in plasma, are outlined.

The BDB, Binary star DataBase http://bdb.inasan.ru combines data of the catalogues of binary and multiple stars of all observational types. There is a number of ways for variable stars to form or to be a part of binary or multiple systems. We describe how such stars are represented in the database., 10 pages, 4 figures

Microscopic instability and macroscopic flow pattern resulting from colliding plasmas are studied analytically in support of laboratory experiments. The plasma flows are assumed to stream radially from two separate centers. In a quasi-planar (2D) geometry, they may arise from an Ohmic explosion of two parallel wires, but similar configurations emerge from other outflows, e.g., colliding winds in binary star systems. One objective of this paper is to characterize the flow instabilities developing near the flow stagnation line. An exact solution for the Buneman-type dispersion equation is obtained without conventional simplifications. The unstable wave characteristics are key to anomalous resistivity that determines the reconnection rate of opposite magnetic fields transported with each flow toward the stagnation zone. The second objective of the paper is to calculate the stream function of the plasma shocked upon collision. We addressed this task by mapping the flow region to a hodograph plane and solving a Dirichlet problem for the stream function. By providing the instability growth rate, responsible for anomalous transport coefficients, and the overall flow configuration, these studies lay the ground for the next step. From there, we will examine the field reconnection scenarios and emerging mesoscopic structures, such as radial striata observed in the experiments., 23 pages, 8 figures, revtex4.1

Precise measurements of galactic cosmic rays revealed a significant difference between the rigidity spectral indices of protons and helium ions. This finding is a notable contrast to the commonly accepted theoretical prediction that supernova remnant (SNR) shocks accelerate protons and helium ions with the same rigidity alike. Most of the earlier explanations for the "paradox" appealed to SNR environmental factors, such as inhomogeneous $p$/He mixes in the shock upstream medium, variable ionization states of He, or a multi-SNR origin of the observed spectra. The newest observations, however, are in tension with most of them. In this paper, we show by self-consistent hybrid simulations that such special conditions are not vital for the explanation of the cosmic ray rigidity spectra. In particular, our simulations prove that an SNR shock can modify the chemical composition of accelerated cosmic rays by preferentially extracting them from a homogeneous background plasma without additional, largely untestable assumptions. Our results confirm the earlier theoretical predictions of how the efficiency of injection depends on the shock Mach number $M.$ Its increase with the charge-to-mass ratio saturates at a level that grows with $M.$ We have convolved the time-dependent injection rates of protons and helium ions, obtained from the simulations, with a decreasing shock strength over the active life of SNRs. The integrated SNR rigidity spectrum for $p$/He ratio compares well with the AMS-02 and PAMELA data., Comment: arXiv admin note: substantial text overlap with arXiv:1707.02744

A two-field model of potential vorticity (PV) staircase structure and dynamics relevant to both beta-plane and drift-wave plasma turbulence is studied numerically and analytically. The model evolves averaged PV whose flux is both driven by and regulates, a potential enstrophy field, $\varepsilon$. The model employs a closure using a mixing length model. Its link to bistability, vital to staircase generation, is analyzed and verified by integrating the equations numerically. Long-time staircase evolution consistently manifests a pattern of meta-stable quasi-periodic configurations, lasting for hundreds of time units, yet interspersed with abrupt ($\Delta t\ll1$) mergers of adjacent steps in the staircase. The mergers occur at the staircase lattice defects where the pattern has not completely relaxed to a strictly periodic solution that can be obtained analytically. Other types of stationary solutions are solitons and kinks in the PV gradient and $\varepsilon$ - profiles. The waiting time between mergers increases strongly as the number of steps in the staircase decreases. This is because of an exponential decrease in inter-step coupling strength with growing spacing. The long-time staircase dynamics is shown numerically be determined by local interaction with adjacent steps. Mergers reveal themselves through the explosive growth of the turbulent PV-flux which, however, abruptly drops to its global constant value once the merger is completed., Comment: 24 pages, 13 figures