bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coulomb Corrections in The Nuclear Statistical Equilibrium Regime
Authors: García D. , Bravo E. 
Published: July 2016

AbstractThe ionic contribution to the Equation of State (EOS) of a multicomponent plasma of nuclei in the nuclear statistical equilibrium regime is studied, and a method to compute the coulombic corrections within the framework of the linear mixing hyphothesis is proposed. Some consequences of including these corrections in the EOS are briefly analysed in relation with two concrete astrophysical scenarios, the Supernovae Ia explosion and the Accretion Induced Collapse of a massive white dwarf.
Plans for the Naval Observatory of Buenos Aires
Authors: Marpegán J. 
Published: July 2016

The Naval Observatory of Buenos Aires was founded In 1860 as a marine observatory to satisfy the needs of nautical and geodetic astronomy in the aid of marine navigation and hydrography. It has provided the official – national time for 50 years.The Observatory carries out computations for the Argentine Nautical Almanac and provides an abridged ephemeris for hydrographic and – topographic work. Since 1955 it has provided standard frequency and time on – the frequencies 5, 10, and 15 MHz through Its transmitting station LOL. During the last two years specific plans were developed for modernizing and – improving the precision of this service. Some of these plans have already been carried out.
Structure of Close Binaries. I: Polytropes
Authors: Naylor M. D. T. , Anand S. P. S. 
Published: July 2016

AbstractAn extension of the method devised by Monaghan and Roxburgh (1965) for rapidly rotating polytropes is used to study the structure of the primary component of a synchronous close binary system. Results are presented for polytropes of index 1.5, 2.0, 3.0, 4.0 and 4.9. We conclude that the extended Monaghan and Roxburgh method can be applied to real stars which are perturbed by both tidal and rotational forces.
The Use of Integrals in Numerical Integrations of theN-Body Problem
Authors: Nacozy Paul E. 
Published: July 2016

AbstractThe numerical integration of systems of differential equations that possess integrals is often approached by using the integrals to reduce the number of degrees of freedom or by using the integrals as a partial check on the resulting solution, retaining the original number of degrees of freedom.Another use of the integrals is presented here. If the integrals have not been used to reduce the system, the solution of a numerical integration may be constrained to remain on the integral surfaces by a method that applies corrections to the solution at each integration step. The corrections are determined by using linearized forms of the integrals in a least-squares procedure.The results of an application of the method to numerical integrations of a gravitational system of 25-bodies are given. It is shown that by using the method to satisfy exactly the integrals of energy, angular momentum, and center of mass, a solution is obtained that is more accurate while using less time of calculation than if the integrals are not satisfied exactly. The relative accuracy is ascertained by forward and backward integrations of both the corrected and uncorrected solutions and by comparison with more accurate integrations using reduced step-sizes.
Dynamics of Plane Stellar Systems
Authors: Hohl Frank 
Published: July 2016

AbstractThe evolution of initially balanced rotating disks of stars is investigated with a computer model for isolated disks of stars. An isolated, initially cold balanced disk is found to be violently unstable. Adding a sufficient amount of velocity dispersion will stabilize all small-scale disturbances. However, the disks are still unstable against slowly growing long wave-length modes and after about two rotations most disks tend to assume a bar-shaped structure. It is found that the final mass distribution over most of the disk can be closely approximated by an exponential variation, irrespective of the initial mass distribution. The gravitational two-stream instability is investigated by means of a modified computer model for infinite doubly periodic stellar systems.
High Resolution Magnetic Field Measurements in the Sunspot Photosphere
Authors: Hofmann Axel , Schmidt Wolfgang , Balthasar Horst , Tarbell Theodore T. , Frank Zoe A. 
Published: July 2016

AbstractWe analysed calibrated Stokes V magnetograms and simultaneously measured Stokes I spectra of high spatial and spectral resolution taken in a medium sized sunspot. We found a clear (anti-) correlation between the brightness variation of penumbral structures and the longitudinal component (B*cosγ) of the magnetic field. No azimuthal variation of the amount of the magnetic field strength (B) was observed across dark and bright structures. There the field is more vertical in bright filaments compared to dark ones.
Coherence Analysis of Photospheric Line Parameters in Active and Non-Active Solar Regions
Authors: Hanslmeier Arnold , Mattig Wolfgang , Nesis Anastasios 
Published: July 2016

AbstractExamples of coherence functions between continuum intensity and line center velocity fluctuations are discussed for non active and active regions. It seems that the magnetic field leads to a different phase shift between intensity and velocity fluctuations than for non active regions.
Magnetohydrodynamic Simulation of the Evolution of Bipolar Magnetic Regions
Authors: Wu S. T. , Yin C. L. , Mcintosh P. , Hildner E. 
Published: July 2016

AbstractIt has been recognized that the magnetic flux observed on the solar surface appears first in low latitudes, and then this flux is gradually dispersed by super granular convective motions and meridional circulation. Theoretically, the magnetic flux transport could be explained by the interactions between magnetic fields and plasma flows on the solar surface through the theory of magnetohydrodynamics.To understand this physical scenario, a quasi-three-dimensional, time-dependent, MHD model with differential rotation, meridional flow and effective diffusion as well as cyclonic turbulence effects is developed. Numerical experiments are presented for the study of Bipolar Magnetic Regions (BMRs). When the MHD effects are ignored, our model produced the classical results (Leighton, Astrophys. J., 146, 1547, 1964). The full model’s numerical results demonstrate that the interaction between magnetic fields and plasma flow (i.e., MHD effects), observed together with differential rotation and meridional flow, gives rise to the observed complexity of the evolution of BMRs.
Formation of Solar Prominences with Normal and Inverse Polarities
Authors: Choe G. S. , Lee L. C. 
Published: July 2016

AbstractNumerical simulations of solar prominence formation are presented employing photospheric horizontal motions as boundary conditions. Three different combinations of magnetic field configurations and footpoint motions are considered: (1) a bipolar arcade with a footpoint shear, (2) an arcade exposed to a shearing and converging motion, (3) two adjacent arcades undergoing a shearing and converging motion. In each case, it is found that the dynamic evolution of magnetic fields can force the plasma into a thermal instability leading to the formation of a prominence.
Measurements of Solar Magnetic Fields Using Radio Observations with the RATAN-600
Authors: Gelfreikh G. B. , Bogod V.M. , Abramov-Maximov V. E. , Tsvetkov S.V. 
Published: July 2016

AbstractThree ways of measuring magnetic fields in the corona and chromosphere have been developed based on spectral polarization observations with high spatial resolution using the radio telescope RATAN-600. The methods rely on effects from the theory of the generation and propagation of microwaves in the solar atmosphere: thermal bremsstrahlung, thermal cyclotron emission, and inversion of the polarization sign in quasi-transverse field regions. The new radio spectrograph (PAS) at the RATAN-600 resulted in higher accuracy measurements of the strength and structure of coronal magnetic fields. Using observations made with the PAS on 1992 January 10, we show that the magnetic field strength in the lower corona above all large sunspots can be measured with an accuracy ≈ 3%. The correlation with photospheric magnetic fields is good, ‘radio’ magnetic fields being weaker by ≈ 20%.
Magnetic Tube Scale and Electron Acceleration from the Fine Structure of Microwave Bursts
Authors: Guang-Li Huang 
Published: July 2016

AbstractA typical microwave burst with fine structures (type Hand) observed by the Dwingloo multi-channel spectrometer is proposed as evidence of a magnetic tube with a small scale and acceleration of electron beams with a short time scale at the source. It is predicted from the observations and theory that the average velocity of non-thermal electrons is about 0.1c and the density of the beam is about 104 cm−3. There is a micro-magnetic tube with a scale length of six hundred kilometers at the microwave source. There is also a quasi-periodic (~ 20 ms) evolution of the beam energy, which may be accelerated by tearing modes. The spectrum of the burst can be explained by the non-uniformity of the magnetic field. The evolution of the spectrum during a single pulse may result from the electron cyclotron maser instability. Hence, information from the fine structure of the spectrum of solar radio bursts is very important for understanding the mechanism of solar flares.
Evidence for Reality of Rapid Solar Radio Fluctuation
Authors: Qijun Fu , Chumin Hu , Bing Zhao , Shenzhen Jin , Yurovsky Yu. , Stepanov A. , Magun A. , Schanda E. 
Published: July 2016

Since fast fine structures (FFS) superimposed on microwave bursts were found with high time resolution observations, they have been observed in extensive frequency range (Slottje 1978; Fu, et al. 1986; Stähli and Magun 1986; and Stepanov and Yurovsky 1991), and these results make understanding of the emission deepening. But, at the same time, the puzzling problem, these phenomena originate from sun or are only artificial, is often concerned and disputed (Benz and Fürst 1987). As it was pointed out by Benz and Fürst (1987), “the only really reliable way to study solar microwave fluctuation is to use two or more widely separated radio telescopes”.In this paper, some of FFS events superimposed on microwave bursts simultaneously obtained at Beijing Astronomical Observatory (BAO), Crimea Astrophysical Observatory (CAO) and Institute of Applied Physics, University of Bern (IAP), are presented at first time. It is a conclusive evidence of rapid radio fluctuation originating from sun and associated with flare appearance.
Study of Calcium-K Network Evolution from Antarctica
Authors: Singh Jagdev 
Published: July 2016

AbstractTo study the evolution and decay of large convective cells known as supergranules, a solar telescope was set up at Maitri, Indian permanent station in Antarctica region during the local summer months (December 1989 through March 1990). A continuous sequence of calcium-K-line filtergrams for 106 hours with an interval of about 10 minute was obtained. The analysis of this data indicates that most probable life time of the calcium K network is about 20 hours. The life time depends upon the size of the cell and is larger for bigger cells. The data also show that cells (of given size) associated with remanent magnetic field regions live longer than those in the region free from magnetic field regions.
Rotation Rate of Active Nests on the Sun
Authors: Van Driel-Gesztelyi Lidia , Van Der Zalm ED B.J. , Zwaan Cornelis 
Published: July 2016

AbstractWe analyse Greenwich sunpot group position data for one solar cycle (1952-1963) in order to study the rotation rate of clusters of sunspot groups, so-called active nests. We find that the latitude-dependent rotation rate of nests shows an intrinsic spread. This spread appears to be caused by extensive and dense clusters of sunspot nests (superclusters or nested nests), and by very compact single nests of short duration. The ‘best’ rotation rate is defined as the rate at which the highest number of sunspot groups appear to form nests. This latitude-dependent best rotation is close to the rotation rate of individual recurrent sunspots, although nests seem to rotate slightly more rigidly than sunspot groups.
Dynamical Effects in Solar Photospheric Flux Tubes
Authors: Hasan S.S. 
Published: July 2016

AbstractThe interaction of an intense flux tube, extending vertically through the photosphere, with p-modes in the ambient medium is modelled by solving the time dependent MHD equations in the thin flux tube approximation. It is found that a resonant interaction can occur, which leads to the excitation of flux tube oscillations with large amplitudes. The resonance is not as sharp as in the case of an unstratified atmosphere, but is broadened by a factor proportional to H−2, where H is the local pressure scale height. In addition, the inclusion of radiative transport leads to a decrease in the amplitude of the oscillations, but does not qualitatively change the nature of the interaction.
Search for Obscured IRAS Galaxies
Authors: Mickaelian A.M. , Hakopian S.A. , Balayan S.K. 
Published: July 2016

AbstractWe have discovered a number of sources still remaining in the IRAS catalogs with no convincing optical identification. Their IR colors and high galactic latitudes indicate faint galaxies (fainter the DSS limit). These empty fields have been observed with the Byurakan Obs. 2.6m telescope in VRI. 22m–23m faint formations have been revealed.
5-GHz VLBI Imaging Observations of 7 Equatorial AGNs
Authors: Shen Z.-Q. , Jiang D. R. , Chen Y.J. , T.-S. Wan  
Published: July 2016

AbstractSince 1992 we have been conducting a 5-GHz VLBI imaging survey of southern and equatorial radio sources. So far, we have published the results of two observing sessions with 26 southern radio sources imaged in total (Shen et al. 1997; 1998). In this paper, we present the preliminary results of the third session of observations of 7 equatorial sources in the sample.
IRAS F02044+0957: A Radio Source in an Interacting System of Galaxies
Authors: Verkhodanov O. V. , Chavushyan V. H. , Mújica R. , Valdés J. R. , Trushkin S. A. 
Published: July 2016

AbstractThe steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio telescope at four frequencies. Optical spectroscopy of the system components was carried out with the 2.1m telescope of the Guillermo Haro Observatory. The observational data allow us to conclude that this object is a pair of interacting galaxies, a LINER and an H II galaxy, at z = 0.093.
New Statistical Methods for Analysis of Large Surveys: Distributions and Correlations
Authors: Petrosian Vahé 
Published: July 2016

Abstract The aim of this paper is to describe new statistical methods for determination of the correlations among and distributions of physical parameters from a multivariate data with general and arbitrary truncations and selection biases. These methods, developed in collaboration with B. Efron of Department of Statistics at Stanford, can be used for analysis of combined data from many surveys with different and varied observational selection criteria. For clarity I will use the luminosity function of AGNs and its evolution to demonstrate the methods. I will first describe the general features of data truncation and present a brief review of past methods of analysis. Then I will describe the new methods and results from simulations testing their accuracy. Finally I will present the results from application of the methods to a sample of quasars.
Digitization of the FBS: Its Future Use and Expected Results
Authors: Mickaelian Areg M. 
Published: July 2016

Abstract The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. Its plates contain low-dispersion spectra for some 20,000,000 objects. The FBS spectra allow selection of objects by their color, broad emission or absorption lines, or SED; to discover, classify and investigate them. The FBS was conducted originally to search for UVX galaxies (1500 Markarian galaxies were discovered). Selection of blue stellar objects, red stars, and identification of IRAS sources have also been done by means of the FBS spectra. All these projects have been carried out by visual inspection of the plates. Digitization will give new possibilities to search for many new objects: new bright QSOs (m<18m), new Markarian (UVX) galaxies, BCDGs, optical counterparts of IR, radio, X-ray and other sources, late-type stars, planetary nebulae, emission-line stars, and white dwarfs; and to study star clusters and clusters of galaxies. The digitized FBS will be available via the Internet and on CDs. Software and an appropriate interface for working with the data will be provided.
Asteroidal recovering in the DENIS survey. A contribution of near-infrared for classifications
Authors: Baudrand A. , Bee- Borsenberger A. , Borsenberger J. , Barucci A. 
Published: July 2016

AbstractThe Deep European Near-Infrared southern sky Survey (DENIS) has been observing the sky since december of 1995, in the three bands I, J, K of the near-infrared, in order to provide to the community a deep and extensive photometric catalogue of stars and galaxies. In addition, the asteroids will be included in the catalogue as any other regular point sources. Therefore, in the frame of asteroidal taxonomies, this project appeared as a good opportunity to enlarge the asteroid colorimetry data base to new colours and more objects. In order to use the DENIS data for our case, we had, as a first step, to determine all the asteroids observed during the survey to recover them in the catalogue of magnitudes. We present here our recovery procedure and our final expectations. The ultimate aim of this study will be to improve our knowledge on the compositional structure of the asteroidal population.
Brief summary of Kleť photographic search programme for minor planets
Authors: Tichá J. , Tichý M. , Moravec Z. 
Published: July 2016

AbstractA long-term photographic search programme for minor planets was begun at the Kleť Observatory at the end of seventies using a 0.63-m Maksutov telescope, but with insufficient respect for long-arc follow-up astrometry. More than two thousand provisional designations were given to new Kleť discoveries. Since 1993 targeted follow-up astrometry of Kleť candidates has been performed with a 0.57-m reflector equipped with a CCD camera, and reliable orbits for many previous Kleť discoveries have been determined. The photographic programme results in more than 350 numbered minor planets credited to Kleť, one of the world's most prolific discovery sites. Nearly 50 per cent of them were numbered as a consequence of CCD follow-up observations since 1994.This brief summary describes the results of this Kleť photographic minor planet survey between 1977 and 1996. The majority of the Kleť photographic discoveries are main belt asteroids, but two Amor type asteroids and one Trojan have been found.
On gas productivity of elongated cometary nucleus in rotation
Authors: Medvedev Yu.D. 
Published: July 2016

AbstractDynamics and distribution of dust and ice particles in the cometary head is investigated for the elongated nucleus in rotation. Three kinds of particles are considered: the dust particles, the ones with volatile fraction and the ice ones. The particles with volatile fraction and sublimated from larger particles are in the cometary head for rather a long time and some abundance of particles and gas can be observed in the region of the head facing the Sun.To estimate the influence of dust density on the gas productivity a numerical simulation was done. The results show that the presence of grains in the coma causes the effects of damping and time delay for gas productivity of an elongated nucleus.
The structure of thermal infrared radiation of the inner coma of comet Hale-Bopp
Authors: Pittichová J. , Käufl H.U. 
Published: July 2016

AbstractThe distribution of the thermal infrared radiation from dust in the inner coma of comet Hale-Bopp (1995 O1), based on observations obtained at ESO, LaSilla, Chile, has been mapped in the 10-/μm atmospheric window on July 16, 1997. A preliminary analysis of the infrared data taken with a resolution of 0.498 arcsec per pixel shows a heterogeneous distribution of the infrared radiation in the inner coma. Three asymmetric brightness peaks (in addition to the nucleus) are apparent. Similar behaviour of the distribution of the infrared brightness was found on all observed spectral bands centered around 8.39 μm, 9.78 μm, 11.65 μm, and 12.56 μm. The spectral energy distribution is compared to black-body curves. The observed distribution of the infrared brightness close to the nucleus could be interpreted by multiple sources of ejected dust particles. Simulated aperture photometry shows only minor deviation from a simple spherically symmetric outflow model.
Numerical modelling of Kuiper belt objects’ dynamics – limitations
Authors: Gabryszewski R. 
Published: July 2016

AbstractThe investigation of KBOs’ dynamics is based on numerical orbital integrations on extremly long time scales due to orbital evolution of particles. The evolution of KBOs to JFCs needs a time-span of order of 109years. Such a long time of integration affects errors. So the question arises what is the boundary of an integration time to distinguish the physical solution from numerical noise and what it depends on. This paper presents numerical integrations of less than 150 massless test particles in the model of the Solar System which consists of 4 giant planets and the central mass. For each test particle computations were repeated at least twice on different computers and using two different methods of integration. The results show that an increase of errors in a solution depends on the eccentricity and the inclination of an orbit. The estimated maximum time-span of integration is of the order of 10 million years for highly elliptic orbits (e 0.6) and up to 125 million years for quasi-circular orbits (for particular model of the Solar System with orbits of massless objects outside Neptune's orbit). After long time-span of integration (120-130 Myrs) the solution can be completely chaotic. It cannot be stated unequivocally that this is one of the possible particle's paths or that this is just a numerical noise. So a different way of studying KBOs’ and SP comets’ dynamical evolution is needed. The integration of equations of motion between particular phases of objects which are considered as comets in different phases of their lives (KBOs − Centaurs − Comets − possibly extinct Comets) could be the new way of studying the dynamical evolution of SP comets.
A Solar Flare Observed with the Smm and Einstein Satellites
Authors: Schmitt J. H. M. M. , Lemen J. R. , Zarro D. 
Published: July 2016

AbstractWe present X-ray observations of the 21 July, 1980 flare which was observed both with the Einstein Observatory Imaging Proportional Counter (IPC) and the X-Ray Polychromator (XRP) and Gamma-Ray Spectrometer onboard the SMM satellite. The Einstein observations were obtained in scattered X-ray light, i.e., in X-rays scattered off the Earth's atmosphere. In this way it is possible to obtain spatially unresolved X-ray data of a solar flare with the same instrument that observed many X-ray flares on other stars. This paper juxtaposes the results and implications of the ‘stellar interpretation’ to those obtained from the far more detailed SMM observations. The result of this ‘calibration’ observation is that the basic properties of the flaring plasma can be reliably determined from the ‘stellar’ data, however, the basic physics issues can only be studied through models.
Stellar Flare Statistics - Physical Consequences
Authors: Shakhovskaya N. I. 
Published: July 2016

AbstractThe observational data permit us to establish clear statistical correlations between different parameters of stellar flare activity and the characteristics of quiet stars. These relations are:
(i)between energies and frequencies of flares on stars of different luminosities;(ii)between total radiation energies of flares and quiet stars both in X-ray and Balmer emission lines;(iii)between flare decay rates just after the maxima and flare luminosities at maxima.