bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overview and Proposition for a Modern Definition of the CEP
Authors: Capitaine Nicole 
Published: July 2016

AbstractThe current IAU conventional models for precession and nutation are referred to the Celestial Ephemeris Pole (CEP). However, the concept corresponding to the CEP is not clear and cannot easily be extended to the most recent models and observations. Its realization is actually dependent both on the model used for precession, nutation and polar motion and on the observational procedure for estimating the Earth orientation parameters. A new definition of the CEP should therefore be given in order to be in agreement with modern models and observations at a microarsecond level. This paper reviews the various realizations of the pole according to the models and observations and discusses the proposals for a modern definition of the CEP that are under consideration within the work of the subgroup T5 entitled “Computational Consequences” of the “ICRS” IAU Working Group.
Construction of Planetary Theory by Iterative Procedure
Authors: Ivanova T.V. 
Published: July 2016

In this paper the method of determination of the planetary perturbations is proposed which is a modification of Dziobek-Brouwer’s method [1,2]. For the simplicity the case of two mutually disturbing planets is considered. In the original version of the method the perturbations of rectangular planetary coordinates are presented by means of the formal integralswhere index i corresponds to the number of the planet; δXik are perbations of Xik coordinates; Gik – components of the perturbating accelerations. The coefficients of aik, cik bij are the well-known functions of the coordinates of the elliptic motion which can be developed as double Fourier series in mean longitudes. The denominators in Davis’ formulas [3] for these coefficients contain the eccentricities. For this reason Musen [4] expressed an opinion that Brouwer’s method would lose its effectiveness when small eccentricities are involved. These fictitious peculiarities are eliminated in the present paper by means of trivial transformations and the expressions for the coefficients are given in a simple symmetric form.
Third-Order Solution of An Artificial-Satellite Theory
Authors: Kinoshita Hiroshi 
Published: July 2016

AbstractA third-order solution is developed for the motions of artificial satellites moving in the gravitational field of the Earth, whose potential includes the second-, third-, and fourth-order zonal harmonics. Third-order periodic perturbations with fourth-order secular perturbations are derived by Hori’s perturbations method. All quantities are expanded into power series of the eccentricity, but the solution is obtained so as to be closed with respect to the inclination. A comparison with the results of numerical integration of the equations of motion indicates that the solution can predict the position of a close-earth satellite with a small eccentricity with an accuracy of better than 1 cm over 1 month.
Classification of C-Rich Stars According to Their Mid-IR Signatures
Authors: Papoular R. 
Published: July 2016

The spectra of the IRAS low-resolution-spectrometer in tape form have been submitted to a systematic morphological analysis, using classical quantitative discriminants (O.Gal et al. 1987, A & A 183, 29; Y. Baron et al. 1987, A & A 186, 271; R. Papoular 1988, A & A , in press). Spectra which display the 11.5μ feature of SiC fall into 4 classes of average spectral excesses. They differ by the width of the SiC feature and by the presence or absence of secondary features at ~8.6, ~11.7 and ~12.8μm.A majority of these spectra have a lower 12-25μm colour temperature than do most optically selected C-stars, presumably because of thicker dust envelopes. While most spectra belong to LRS class 4n, 20% of the total were found among the brightest 20% of the much larger class In, suggesting that the relative abundance of C-stars is much higher than previously assumed.
Mass-Losing Peculiar Red Giants: The Comparison Between Theory and Observations
Authors: Jura M. 
Published: July 2016

AbstractThe mass loss from evolved red giants is considered. It seems that red giants on the Asymptotic Giant Branch (AGB) are losing between 3 and 6 10-4 MΘ kpc-2 yr-1 in the solar neighborhood. If all the main sequence stars between 1 and 5 MΘ ultimately evolve into white dwarfs with masses of 0.7 MΘ the predicted mass loss rate in the solar neighborhood from these stars is 8 10-4 MΘ kpc-2 yr-1. Although there are still uncertainties, it appears that there is no strong disagreement between theory and observation. However, it could also be that we have not yet identified much of the source of the mass-loss from pre-white dwarf stars.
Absorption Spectrum of RCrB During the Light Minimum
Authors: Rao N. Kameswara , Giridhar S. , Ashoka B.N. 
Published: July 2016

Observations of RCrB obtained during the 1986 and early part of 1963 light minima show the following changes relative to the spectrum obtained at maximum light.The molecular band of C2 (Swan System), CN bands at λ4215 and low excitation metal lines are enhanced in absorption.
Report of the Sub-Group on Time
Authors: Guinot B. 
Published: July 2016

The report of the Sub-Group on Time (SGT) of the IAU Working Group on Reference Systems (WGRS) is divided as follows.Sections 2 to 4 recall the scope of the work of the SGT and briefly describe its activity.Section 5 summarizes the discussions on several topics which form the background of the draft recommendations and notes of Section 6.
Preliminary Report of the Work of the Subgroup on Coordinate Frames and Origins
Authors: Kovalevsky J. 
Published: July 2016

The membership of the subgroup on coordinate frames and origins included the following: V.K. Abalakin, S. Aoki, F. Arias, С Boucher, N. Capitaine, K. Johnston, J. Kovalevsky (chairman), C. Ma, I.I. Mueller, C.A. Murray, H. Schwan, C.A. Smith, C. de Vegt and R. Wielen.In addition, the following colleagues have contributed to the work: V.A. Brumberg, T. Damour, J. Dickey, M. Feissel, T. Fukushima, B. Guinot, T. Huang, M. Standish, J.G. Williams and B.X. Xu.
Consistency of Nutation Modeling in Radio Source Position Comparisons
Authors: Sovers O.J. 
Published: July 2016

AbstractComparisons between sets of radio source coordinates determined from independent VLBI measurements show that rotational offsets can be as large as several milliarcseconds (mas), and are considerably larger than the positional uncertainties (≤1 mas). The 1 to 2 mas discrepancies remaining after removal of the rotational offsets indicate the present true level of accuracy. Analyses of DSN and CDP astrometric data are performed to explore the effects of alternative schemes of nutation modeling on such catalog comparisons. It is concluded that rotations between different source catalogs are minimized or eliminated if the nutation models employed are consistent. Intrinsic source coordinate discrepancies, however, remain at the 1 mas level.
Comment on the Definition of the Nonrotating Origin
Authors: Eichhorn Heinrich 
Published: July 2016

AbstractThe paper gives a rigorous and purely formal derivation for the relationship between the “nonrotating” origin and the x-axis of the Qt system, i.e., the true equator system. Neglecting nutation, a nonrotatingorigin could also be achieved by putting m=0 in the formula for the time derivative of right ascension.
On the Determination of an Astrometric Center of a Quasar
Authors: Galas Roman 
Published: July 2016

AbstractThe influence of optical structure of compact extragalactic radio sources on the definition of their centroids is discussed. Numerical calculations are performed using 4C 31.63 as an example. The results show that the presence of the underlying luminous galaxy does not lead to an unusual decrease of the accuracy in the optical astrometric measurements.
Close Approach Astrometry: A Method for Improving Reference Systems
Authors: Nakamura T. , Shibasaki H. 
Published: July 2016

AbstractFor improved establishment of the dynamical reference frame and tying it to the stellar reference frame, a method to observe close approach (CA) events between satellite and satellite and/or satellite and star is proposed here. The accuracy of measurements of angular distance is 0”.02 – 0”.03 for a single data point. We apply this technique fairly successfully to the CA events of the Galilean satellites and a preliminary orbital longitude correction to the E2X3 constants of J4 is obtained from eight CA observations ranging from 1987 to 1989.
On Precession and Nutation Values
Authors: Vicente R.O. 
Published: July 2016

AbstractThe results of research on the Earth’s theory of rotation are presented, comparing observed and theoretical values specially for the luni-solar precession and nutation. Investigations of geodynamics show the strong dependence of the nutation values on the adopted model for the structure of the Earth, while the values referring to the precession are not affected as much. The new observational techniques are able to determine some of these values with greater precision than the classical optical techniques, but it is essential that the observations should be done in a systematic and regular way for several decades.
Periodic Variation of the North-South Asymmetry of Solar Activity Phenomena
Authors: Verma V. K. 
Published: July 2016

AbstractWe report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data for the period 1936–1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998. Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested by Verma.
Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles
Authors: Rušin Vojtech , Minarovjech Milan , Rybanský Milan 
Published: July 2016

AbstractLong-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.
Helioseismology and the Solar Interior Dynamics
Authors: Vauclair S. 
Published: July 2016

AbstractThe inversion of helioseismic modes leads to the sound velocity inside the Sun with a precision of about 0.1 per cent. Comparisons of solar models with the “seismic sun” represent powerful tools to test the physics: depth of the convection zone, equation of state, opacities, element diffusion processes and mixing inside the radiative zone. We now have evidence that microscopic diffusion (element segregation) does occur below the convection zone, leading to a mild helium depletion in the solar outer layers. Meanwhile this process must be slowed down by some macroscopic effect, presumably rotation-induced mixing. The same mixing is also responsible for the observed lithium depletion. On the other hand, the observations of beryllium and helium 3 impose specific constraints on the depth of this mildly mixed zone. Helioseismology also gives information on the internal solar rotation: while differential rotation exists in the convection zone, solid rotation prevails in the radiative zone, and the transition layer (the so-called “tachocline”) is very small. These effects are discussed, together with the astrophysical constraints on the solar neutrino fluxes.
Tomography of the Solar Wind using Interplanetary Scintillation
Authors: Oberoi Divya , Rao A. Pramesh 
Published: July 2016

Extended AbstractInterplanetary scintillation (IPS) measurements are sensitive to a weighted sum of the properties of solar wind (SW) along the line-of-sight (los) to a distant compact radio source. Mapping alosback to the surface of the Sun provides information of the sites of origin of the SW sampled by thelos. By observing different sources, lines-of-sight can be so chosen that they sample overlapping regions of Solar surface. In addition, the rotation of the Sun causes the long lived features in the SW to co-rotate, much like the twirling skirt of a ballerina, presenting different perspective views to the Earth based observers. These properties raise the possibility that systematic IPS observations can be inverted to give the maps of density and the velocity of the SW in the inner heliosphere, using techniques similar to tomography.
Chaos and order in the Rotational Motion
Authors: Maciejewski Andrzej J. 
Published: July 2016

AbstractIt was proved that the problem of perturbed planar oscillations of a rigid-body in a circular orbit is nonitegrable. Two types of perturbations were considered: solar radiations pressure and the third body torques. In the second part of the paper example of chaotic rotations of a symmetric rigid body in a circular orbit was given. It was shown numerically that the phase space is divided into two separate regions of chaotic and ordered motions.
The Stochasticity of Motions in the Triplets of Stars and Galaxies
Authors: Anosova J.P. , Kiseleva L.G. , Chernin A.D. , Ivanov A.V. , Orlov V.V. 
Published: July 2016

AbstractThe dynamical instability of motions is studied numerically for the triplets of stars and galaxies. The models of equal-mass components which are in rest initially, are investigated. The divergence of initially near by trajectories close to exponential one is observed in the configurational as well as the phase space. The characteristic time of such divergenee is less for the configurations which are initially hierarchical. The presence of significant dark matter distributed over the whole volume of system speeds up the rate of stochastisation considerably.
On Dynamical Non-Stationarity of the Galaxy Systems
Authors: Anosova J.P. , Kiseleva L.G. , Orlov V.V. 
Published: July 2016

AbstractBy the computer simulations we have studied a behaviour of the virial coefficient k(t) for the triples and quintets of galaxies as a function of time. In a number of cases some quasiperiodical oscillations k(t) have been observed; these variations are resulted from an existence of the temporary binary subsystems. Strong negative correlation between k and rmin (rmin is a minimum separation between the bodies) is observed. A presence of a large hidden mass Mn distributed around a triple increases the degree of stochasticity of the process k(t) and decreases the correlation between k and rmin. The process k(t) must not been considered as a random one, as the autocorrelation function does not show any decreasing of the oscillation amplitude with a grow of time.
Formation of Large Sacle Structures in the Universe by Inverse Cascade: Cosmosynergetics
Authors: Krishan V. , Sivaram C. 
Published: July 2016

AbstractIt is suggested that inverse cascade that may occur in the turbulent cosmic medium can result in the formation of very large scale structures in the universe, upto the largest scales like the Great Wall. Again clustering of galaxies on all scales is interpreted to be due to these self-organisation processes occurring in a turbulent medium, the largest structures being anisotropic and nearly two dimensional, the smaller structures remaining isotropic. The observed fractal distribution of galaxies is also interpreted on this basis. The direct proportionality between the flow velocity and the linear dimension of the structure may show a way out of the dilemma of missing matter.
Dynamic Modelling Transformations for the Low Earth Orbit Satellite Particulate Environment
Authors: McDonnell J.A.M. , Sullivan K. , Green S.F. , Stevenson T.J. , Niblett D.H. 
Published: July 2016

AbstractA simple dynamic model to investigate the relative fluxes and particle velocities on a spacecraft’s different faces is presented. The results for LDEF are consistent with a predominantly interplanetary origin for the larger particulates, but a sizable population of orbital particles with sizes capable of penetrating foils of thickness &lt;30μm. Data from experiments over the last 30 years do not show the rise in flux expected if these were space debris. The possibility of a population of natural orbital particulates awaits confirmation from chemical residue analysis.
Face-Dependent Impact Probabilities Upon LDEF for Heliocentric Particle Orbits
Authors: Steel Duncan 
Published: July 2016

AbstractIf the impact record upon LDEF is to be interpreted so as to determine the flux, orbits, sizes and compositions of natural meteoroids and dust, and space debris, then it is necessary to relate the microcraters and perforations recorded to the likely source orbit of the particle in each case. Here a single-particle approach is used to calculate the relative impact probabilities upon six orthogonal faces of LDEF for particles coming from heliocentric orbits confined to the ecliptic; the results are presented as functions of impact velocity and impact angle for each face. The flux from geocentric orbits to the Space-and Earth-pointing faces is much lower than to the other faces; experiments positioned on those faces are thus likely to be less contaminated by space debris. Particles from heliocentric orbits can impact both the Space and Earth faces, but the latter is less likely to be hit due to the shadowing effect of the planet. The cratering ratios for the East (or leading) face compared to the West (or trailing) and the Earth-directed faces are strongly dependent upon the velocities of the particles and can therefore indicate of the velocity distribution of meteoroids and interplanetary dust.
Light Scattering by Solar System Dust: The Opposition Effect and the Reversal of Polarization
Authors: Muinonen K. , Lumme K. 
Published: July 2016

The opposition effect and the reversal of linear polarization, or negative polarization, at small phase angles have been almost universally observed in light scattered from atmosphereless solar system bodies (e.g., Seeliger 1887, Lyot 1929). Recent investigations have indicated that both phenomena can be qualitatively understood as resulting from a common physical mechanism: coherent multiple backscattering (Shkuratov 1989, Muinonen 1989). These findings have cast doubt on the hitherto accepted explanation that mutual shadowing alone is responsible for the opposition effect, and for the first time offer an acceptable interpretation of the polarization reversal near opposition. As for interplanetary dust, the coherent backscattering mechanism contributes both to the Gegenschein and to the almost certainly existing negative polarization branch (Roosen 1970, Lumme and Bowell 1985).In the following, theoretical results supporting the coherent backscattering explanation are briefly presented. As future work, we suggest modeling light scattering by a particulate medium to include the first, second and, if necessary, higher orders of scattering in the range below the typical particle size.
Methods, Difficulties, and First Results in Laboratory Simulation of Cosmic Dust Electric Charging
Authors: Svestka J. , Grün E. 
Published: July 2016

AbstractParticles of radii 0.2 to 3 μm and of different materials were suspended in an electrodynamic quadrupole inside a vacuum chamber and exposed to beams of electrons and ions of energies up to 20 keV and 5 keV, respectively, with the aim to simulate electric charging of cosmic dust particles. It was found that the equilibrium surface electrostatic potential of glass particles of radii 0.2 to 2 μ charged by electrons of energies 1 to 20 keV is always positive. This can be explained by secondary electron emission at lower energies of electrons and by penetration of electrons through particles with subsequent secondary electron emission mainly from the exit side at higher energies. In case of charging by ions electrostatic potential of particles is generally much lower than expected values and interpretation of results of measurement is more complicated. The most promising way to eliminate instrumental influences disturbing processes of charging seems to be a construction of a smaller suspension system in which these influences would be negligible. Parameters of such a suspension system were derived from results of measurements.
Plasma Emission from High Velocity Impacts of Microparticles Onto Water Ice
Authors: Timmermann R. , Grün E. 
Published: July 2016

AbstractCollisions of icy objects play a major role in the outer solar system. The purpose of this investigation is the experimental study of plasma production by dust impacts on icy surfaces. Impact speeds ranged from 3 to 60 km/s. It was found that the dominant ion species which were released are both positive and negative water clusters. The impact charge yield from icy surfaces is approximately a factor 100 below that from previously studied gold surfaces.
Interstellar and Stellar Abundances Across the Galactic Disk
Authors: Peimbert Manuel 
Published: July 2016

Abstract.Observational evidence related to the chemical composition across the disk of the Galaxy is reviewed. The H2density distribution derived for the Galaxy is poorly known, consequently it is still not possible to compare theoretical models of the chemical evolution of the Galaxy with the gaseous density distribution. The H2density distribution is particularly sensitive to the fraction of carbon atoms embedded in CO molecules and to the possible presence of a C/H abundance gradient.
Metal Enrichment in the First Ages of the Galaxy
Authors: Spite F. , Spite M. 
Published: July 2016

It is obviously interesting to study in detail the chemical composition of extreme Population II stars since they may give indications about the processes which took place in the very first ages of the Galaxy.It is well known that de abundance of metals in the stars of extreme Population II are smaller than in Population I stars, but it is not yet clear from the literature if all the metals, in all the metal deficient stars, are deficient by the same factor or not. However some anomalies were shown in some halo stars : over-deficiency of barium, “s process” element (Pagel 1965), over-deficiency of odd elements (Arnett 1971, Peterson 1976). These differences are however difficult to measure and are not very much larger than the possible errors of the analysis, so that according to Trimble 1975 they are “not proven”.