bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compressive Sensing: Analysis of Signals in Radio Astronomy
Authors: Gaigals G. , Greitāns M. , Andziulis A. 
Published: February 2017

Abstract
The compressive sensing (CS) theory says that for some kind of signals there is no need to keep or transfer all the data acquired accordingly to the Nyquist criterion. In this work we investigate if the CS approach is applicable for recording and analysis of radio astronomy (RA) signals. Since CS methods are applicable for the signals with sparse (and compressible) representations, the compressibility of RA signals is verified. As a result, we identify which RA signals can be processed using CS, find the parameters which can improve or degrade CS application to RA results, describe the optimum way how to perform signal filtering in CS applications. Also, a range of virtual LabVIEW instruments are created for the signal analysis with the CS theory.
Modeling of Highly-Excited Atomic Level Populations in Astrophysical Plasmas
Authors: Docenko Dmitrijs 
Published: February 2017

Abstract
Recombination lines arising in transitions between highly-excited atomic levels are becoming increasingly used for the plasma diagnostics, as the sensitivity of astronomical instrumentation increases. This paper describes a model used to compute the level population of the Rydberg levels and gives a collection of hydrogenic approximation expressions that can be used to estimate the relevant atomic data. The Rydberg level populations may also be used to estimate level-specific recombination rate for lower atomic levels accounting for the electron cascade. The expressions are applied to predict the radio recombination line spectrum of the fast-moving knots of the Cassiopeia A supernova remnant.
Diffusional Separation of Calcium Isotopes in Chemically Peculiar Stellar Atmospheres
Authors: Sapar L. , Sapar A. , Poolamäe R. , Aret A. 
Published: February 2017

Abstract
Diffusional separation of calcium isotopes in the atmospheres of hot chemically peculiar stars is studied. In addition to the usual radiative acceleration effect, the light-induced drift is taken into account. We propose that microturbulence in stable stellar atmospheres is generated by the interaction between plasma particles and radiative flux. Formulae for the microturbulent velocity and microturbulence diffusion coefficient are derived. Data on isotopic and hyperfine splitting of the calcium spectral lines have been collected as an input file. The equilibrium Ca isotope concentrations are found in model computations, iteratively correcting the radiative acceleration values. The general picture of Ca isotope stratification is found to be similar to our previous results obtained for Hg isotopes: dominating overabundance of the heaviest isotope. Diffusional stratification of Ca isotope concentrations in atmospheres of late B and early A spectral types are computed and visualized in figures. The isotope abundances on the inner boundary surface were fixed to be the solar ones. The computed Ca II infrared triplet line profiles are compared with the observed line profiles in a high-dispersion spectrum of HD 175640.
Stochasticity in Star Clusters: Reduced Random Sampling Method
Authors: de Meulenaer P. , Narbutis D. , Mineikis T. , Vansevičius V. 
Published: February 2017

Abstract
This paper aims to contribute to the debate taking place nowadays on the two extreme schemes of sampling the stellar masses within star clusters, known as Optimal Sampling and Random Sampling. We propose a new method for sampling of stellar masses in star clusters which allows a continuous transition between the Optimal Sampling and the Random Sampling. We use a sample of young star clusters from the literature to calibrate the amount of stochasticity generated by the proposed method.
Orbits of the Asteroids Discovered at the Molėtai Observatory in 2000–2004
Authors: Černis K. , Wlodarczyk I. , Zdanavičius J. 
Published: February 2017

Abstract
The paper presents statistics of the asteroids observed and discovered at the Molėtai Observatory, Lithuania in 2000–2004 within the project for astrometric observations of the near-Earth objects (NEOs), the main belt asteroids and comets. CCD observations of asteroids were obtained with the 35/51 cm Maksutov-type meniscus telescope and the 1.65 m Ritchey-Chretien reflector. In the Minor Planet Circulars and the Minor Planet Electronic Circulars (2000–2004) we published 6629 astrometric positions of 1114 asteroids. Among them 78 were newly discovered asteroids at Molėtai, a few NEOs were found by our team independently. For the 67 asteroids discovered at Molėtai the precise orbits were calculated. Because of small number of observations, a few asteroids have low-precision orbits and some asteroids have been lost. For seven objects we present their ephemerides for 2015.
Catalogue of Bright IDS Stars with Extensive Cross-Identifications
Authors: Lipaeva N. A. , Sementsov V. N. , Malkov O. Yu. 
Published: February 2017

Abstract
A new catalogue of bright binary stars is presented. The catalogue1 includes bright IDS systems and bright spectroscopic binaries. Besides IDS data (coordinates, relative positions, magnitudes and spectral classification), the catalogue contains extensive cross-identification and comments for 27452 systems. The catalogue is complete to the 9th mag, but also contains stars down to about 16th mag.
Fractal Properties of the Solar Neighborhood Based on the Geneva-Copenhagen Survey
Authors: Chumak O. V. , Rastorguev A. S. 
Published: February 2017

Abstract
This study analyzes the fractal properties of the space distribution of stars in the solar neighborhood, based on the Geneva-Copenhagen Survey data. We demonstrate the existence of dynamically weakly coupled stochastic fractal structures in the circumsolar stellar medium. The number of such structures in the real stellar medium on 3 to 20 pc scales significantly exceeds the number of similar structures in the corresponding simulated random distributions. The total number of fractal structures depends on their characteristic size – the scale factor (Mf). We demonstrate that the structuredness of the stellar medium increases with the scale factor reaching its maximum around Mf ~ 18 pc and has a minimum around Mf ~ 5 pc. For Mf = 5 pc, the number of fractal structures in the survey is equal to 688, while for Mf = 18−20 pc the corresponding number exceeds 4000, which differs by more than three standard deviations from the mean fractal dimension D for random distributions. Practically, no structures are observed in random distributions in this domain of fractal dimensions. The proportion of fractal structures with [Fe/H]> 0 increases slowly with increasing scale factor and the number of such structures remains in the interval from 170 to 900. On the whole, the number of structures with [Fe/H]< 0 varies with scale factor in the same way as the total number of structures, and lies in the interval from 530 (Mf = 5 pc) to 3200 (Mf = 20 pc). Such significant differences between the fractal properties of the real stellar medium and its random simulations are due to peculiar “gravitational viscosity” of the gravitating medium. The results reported may play an important part in the study of structural properties and dynamic processes in the Galaxy and in the investigation of relaxation processes in particular.
Determination of the Solar Galactocentric Distance from the Kinematics of Masers
Authors: Bajkova A. T. , Bobylev V. V. 
Published: February 2017

Abstract
We determine the parameters of Galactic rotation and the solar galactocentric distance R
0 by simultaneously solving Bottlinger’s kinematic equations using data for masers with known line-of-sight velocities and highly accurate VLBI trigonometric parallaxes and proper motions. Our sample includes 93 masers spanning the range of galactocentric distances R from 3 to 15 kpc. The inferred parameters are Ω0 = 29.7 ± 0.5 km s−1 kpc−1, Ω′0 = −4.20 ± 0.11 km s−1 kpc−2, Ω″0 = 0.730 ± 0.029 km s−1 kpc−3, and R
0 = 8.03 ± 0.12 kpc, implying a circular rotation velocity of V
0 = 238 ± 6 km s−1 at the solar distance R
0.
Distribution and Kinematics of Classical Cepheids in the Galactic Outer Ring
Authors: Mel’nik A. M. , Rautiainen P. , Berdnikov L. N. , Dambis A. K. , Rastorguev A. S. 
Published: February 2017

Abstract
The existence of an outer ring in the Galaxy can explain the kinematics of OB associations in the Perseus and Sagittarius stellar-gas complexes. Moreover, it can also explain the orientation of the Carina arm with respect to the major axis of the bar. We show in this paper that the morphological and kinematical features of the sample of classical Cepheids are consistent with the presence of an R
1
R′2 ring in the Galaxy.
The Mechanism and Timescale of Nodal Precession: Two Nuclear Stellar Disks in the Galactic Center
Authors: Kondratyev B. P. 
Published: February 2017

Abstract
A dynamical model of interacting nuclear stellar rings in the central parsec of our Galaxy is constructed. We discuss the physical sources of nodal precession and of the associated time scales. For approximate study of the mutual orbital precession, we replace broad nuclear rings by weighted average narrow circular rings. The model with narrow circular rings is shown to adequately describe the nodal precession. The period of relativistic apsidal precession in the center of the Galaxy,

T

ap

•

≈
5
⋅

10

8

yr

$T_{{\rm{ap}}}^ \bullet \approx 5 \cdot 10^8 \, {\rm{yr}}$

, is almost an order of magnitude longer that the period of nodal precession, T
nod ≈ 7 · 107 yr, due to gravitational perturbations of nuclear disks (or rings). An important property of the nodal precession of nuclear rings is established: the lines of nodes of the two rings rotate uniformly with the same angular velocity, but in different directions. This explains the important observational fact that the lines of nodes of nuclear disks are not collinear, but are directed at large angles to each other.
Galactic Spiral Pattern beyond the Optical Size Induced by the Triaxial Dark Halo
Authors: Butenko M. , Khoperskov A. , Khoperskov S. 
Published: February 2017

Abstract
We suggest a possible mechanism for the formation of non-tidal gaseous structures in galactic outskirts. According to recent observations, extended spiral structures are detected beyond the optical radii R
opt in numerous disk galaxies. Such features can be clearly seen in deep HI and UV images (e.g., NGC 3198, NGC 3359, NGC 2841, NGC 3198). We argue, based on our gas-dynamical simulations, that such outer spirals could form as a result of the interaction of the galactic disk with the triaxial host dark matter halo.
High Resolution Gravitational Lens Model
Authors: Chechin L. M. 
Published: February 2017

Abstract
A new model of gravitational lens – high-resolution gravitational lens based on the metric of gravitational field produced by N moving and rotating finite-sized bodies – is proposed. The model is applied to the case of a double galaxy gravitational lens. It is pointed out that previous searches for gravitational lensing in double systems focused on eclipsing binaries and were based on the analysis of their photometric variability. Unlike other authors, we determined the extra terms to be added to the refraction angle to account for the motion and rotation of the bodies. We show that the allowance for the motion of galaxies decreases the shifts of the images of the lensed object and that this effect is detectable in the current state of astronomical observations.
BSDB: A New Consistent Designation Scheme for Identifying Objects in Binary and Multiple Stars
Authors: Kovaleva D. A. , Malkov O. Yu. , Kaygorodov P. V. , Karchevsky A. V. , Samus N. N. 
Published: February 2017

Abstract
The new consistent scheme for designation of objects in binary and multiple systems, BSDB, is described. It was developed in the frame of the Binary star DataBase, BDB (http://www.inasan.ru), due to necessity of a unified and consistent system for designation of objects in the database, and the name of the designation scheme was derived from that of the database. The BSDB scheme covers all types of observational data. Three classes of objects introduced within the BSDB nomenclature provide correct links between objects and data, what is especially important for complex multiple stellar systems. The final stage of establishing the BSDB scheme is compilation of the Identification List of Binaries, ILB, where all known objects in binary and multiple stars are presented with their BSDB identifiers along with identifiers according to major catalogues and lists.
Star Formation and Galaxy Dynamo Equations with Random Coefficients
Authors: Mikhailov E. A. , Modyaev I. I. 
Published: February 2017

Abstract
We study the influence of star formation on magnetic field in galaxies. Two approaches have been used to describe this mechanism. The first one uses some averaged approximate kinematic characteristics that appear in the galactic dynamo equations. We use the so-called no-z model that takes into account the fact that galactic disks are quite thin and hence we can consider only the field components that are parallel to the plane of the galaxy. We also use the equation that describes the evolution of magnetic helicity, which can be important for galaxies with intensive star formation. The second approach uses the dynamo equations with random coefficients, which are useful for describing magnetic fields in galaxies with rapidly changing kinematic parameters. Both methods yield similar results: if the surface star formation rate is small, the magnetic field evolution does not change very much. If the surface star formation rate is more than five times higher than in the Milky Way, the field decays.
Stochasticity of Galactic Orbits of Star Clusters
Authors: Smirnova L. V. 
Published: February 2017

Abstract
The Lyapunov, Lagrange and Poincaré criteria are tested for orbits of 461 open clusters in an axisymmetric potential. Lyapunov exponents and Poincaré sections are computed, and all of the trajectories are found to be stable according to the Lagrange and Poincaré stability criteria. At the same time, some trajectories appear to exhibit minor instability according to the Lyapunov stability criterion.
Optics for Nano-Satellite X-Ray Monitor
Authors: Tichý Vladimír , Burrows David N. , Prieskorn Zachary , Hudec René 
Published: February 2017

Abstract
The Schmidt lobster eye design for a grazing incidence X-ray optics provides a field of view of the order of many degrees, for this reason it can be a convenient approach for the construction of space X-ray monitors. It is possible to assemble Schmidt lobster eye telescopes with the dimensions and focal lengths acceptable for nano-class satellites. In this paper, a draft of nano-class space mission providing monitoring of specific sky areas is presented. A preliminary optical design study for such mission is performed. Two of possible optical designs are presented, for which the field of view, the effective input area and other basic optical parameters are calculated. Examples of the observed images are also presented.
A Young Star Cluster in the Leo a Galaxy
Authors: Stonkutė R. , Narbutis D. , Bridžius A. , Leščinskaitė A. , Vansevičius V. 
Published: February 2017

Abstract
We report a serendipitous discovery of a star cluster in the dwarf irregular galaxy Leo A. Young age (~28 Myr) and low mass (~510 M
⊙) estimates are based on the isochrone fit assuming a metallicity derived for HII regions (Z = 0.0007). The color-magnitude diagrams of the stars, located in and around the cluster area, and the results of aperture photometry of the cluster itself are presented.
Artificial Star Test for Crowded Field CCD Photometry
Authors: Stonkutė R. , Vansevičius V. 
Published: February 2017

Abstract
A new method of performing an artificial star test (AST) for crowded field stellar CCD photometry is proposed. This AST method is superior in the cases when it is necessary to account for varying photometric quality across the study field, arising due to crowding variations. For this purpose, the color-magnitude diagrams (CMDs) of AST stars with statistically reliable error estimates, as well as completeness maps, can be generated at a required spatial resolution.
Ultraviolet and Infrared Correlation Studies in Orion
Authors: Bose Lakshmi S. , Sujatha N. V. , Narayanankutty K. 
Published: February 2017

Abstract
We have studied the variation of diffuse ultraviolet (UV) radiation in the northern part of the Orion constellation using a set of eight areas of the GALEX All-Sky Imaging Survey in the far and near UV. Different components of diffuse UV radiation, like dust scattered emission and H2 fluorescence, were quantified and separated after removing the point sources and the foreground emission in each of the fields. Then the dependence of the individual UV components on the infrared 100 μm dust emission was studied. We did not find any positive correlation between the diffuse-UV and IR-100 micron intensities, probably due to the high optical depth of the region or the entire dust column not contributing to the diffuse UV radiation. However, in the far UV we noticed the presence of an excess emission in addition to the dust scattered radiation, which is clearly absent in the near UV. This excess emission, identified as the H2 fluorescence, is produced by the Trapezium stars in the surrounding molecular clouds. We also compare our results with those of previous studies in the region, based on Far Ultraviolet Spectroscopic Explorer (FUSE) observations.
Ultraviolet Spectroscopic Investigation of HU Aqr and AN UMa with the Data from HST and IUE
Authors: Sanad M. R. 
Published: February 2017

AbstractWe present ultraviolet spectroscopic study of two polar systems, HU Aqr and AN UMa, observed with the Hubble Space Telescope’s Space Telescope Imaging Spectrograph (STIS) and Faint Object Spectrograph (FOS) and with the International Ultraviolet Explorer (IUE) during the period 1979–2003, to diagnose the ultraviolet fluxes of CIV 1550 Å and He II 1640 Å emission lines originating in an accretion stream during different orbital phases. The reddening of two systems is determined from the 2200 Å absorption feature. Different spectra for both systems, showing the variations in line fluxes at different orbital phases, are presented. We concentrated on calculating the line fluxes of CIV and He II emission lines. From HST and IUE data, we derived accretion luminosities and accretion rates for the two systems. The average temperature of the accretion stream for HU Aqr and AN UMa is about 5000 K and 6000 K, respectively. Our results show that there are variations in line fluxes, accretion luminosities and accretion rates with time for the two systems. These modulations are attributed to the variations of both density and temperature as a result of a changing rate of mass transfer from the secondary star to the primary star. These results from the HST and IUE observations support the irradiation model producing sufficient ultraviolet flux for orbital modulations.
Statistical Analysis of a Comprehensive List of Visual Binaries
Authors: Kovaleva D. , Malkov O. , Yungelson L. , Chulkov D. , Yikdem G. M. 
Published: February 2017

AbstractVisual binary stars are the most abundant class of observed binaries. The most comprehensive list of data on visual binaries compiled recently by cross-matching the largest catalogues of visual binaries allowed a statistical investigation of observational parameters of these systems. The dataset was cleaned by correcting uncertainties and misclassifications, and supplemented with available parallax data. The refined dataset is free from technical biases and contains 3676 presumably physical visual pairs of luminosity class V with known angular separations, magnitudes of the components, spectral types, and parallaxes. We also compiled a restricted sample of 998 pairs free from observational biases due to the probability of binary discovery. Certain distributions of observational and physical parameters of stars of our dataset are discussed.
Equilibrium Figures inside the Dark-Matter Ring and the Shapes of Elliptical Galaxies
Authors: Kondratyev B. P. , Trubitsyna N. G. , Kireeva E. N. 
Published: February 2017

AbstractWe solve the general problem of the theory of equilibrium figures and analyze two classes of liquid rotating gravitating figures residing inside a gravitating ring or torus. These figures form families of sequences of generalized oblate spheroids and triaxial ellipsoids, which at the lower limit of the tidal parameter
Astronomical Data Resources for Binary and Multiple Stars
Authors: Kovaleva D. 
Published: February 2017

AbstractBinary stars form a significant part of stellar population. They are registered and observed by a number of methods. This is the reason for variety of present-day resources of astronomical data dealing with binaries and multiples. The review of observational types of binary stars and of basic data resources for them is presented. The properties of stars within these types and possible relationships between them are discussed. The Binary star DataBase, BDB (http://bdb.inasan.ru), is presented as the resource joining data for all observational types of binaries. The problem of correct cross-identification of objects within binary and multiple stars is being solved in the frame of the Identification List of Binaries (ILB).
Archives of Astronomical Spectral Observations and Atomic/Molecular Databases for their Analysis
Authors: Ryabchikova T. , Pakhomov Yu. 
Published: February 2017

AbstractWe present a review of open-source data for stellar spectroscopy investigations. It includes lists of the main archives of medium-to-high resolution spectroscopic observations, with brief characteristics of the archive data (spectral range, resolving power, flux units). We also review atomic and molecular databases that contain parameters of spectral lines, cross-sections and reaction rates needed for a detailed analysis of high resolution, high signal-to-noise ratio stellar spectra.
Local Tendencies in Urban Design Viewed Through the Case Study of Contemporary Development Design in Context of Traditional Architecture
Authors: Grbić Mirko , Tomanović Dušan , Gabrijelčič Peter 
Published: February 2017

Abstract
Villages with significant artistic and cultural value have been developed throughout centuries of turbulent past of Montenegrin coastal and hinterland area. Today, these settlements represent a valuable source of information and are a common subject of research and inspiration to many architects. Through the example of recently designed development, this research aims to show the methods and advantages of contemporary design in traditional context. The review of the traditional architecture and urban design gives insight into qualitative and functional characteristics of building styles that witness centuries of experience and are therefore considered as sustainable. Methodological reference to the traditional building construction considers all the influencing factors that determine the qualitative and functional advantages of local ways of construction. The aim of the research is to implement the research process and to initiate the revival of traditional settlements in order to regain the significance they used to have, in contrast to the presently failed urban attempts. There is a tendency to give preference of designing in context of traditional architecture, considering the advantage of such constructions.