bluuebunny/crossref_metadata_2025_split huggingface dataset:
SLR Contribution to Investigation of Polar Motion
Authors: Malkin Zinovy 
Published: July 2016

AbstractThe Satellite Laser Ranging (SLR) technique has been used to determine Earth Rotation Parameters (ERP) for over twenty years. Most of results contributed to the International Earth Rotation Service (IERS) are based on analysis of observations of Lageos 1 & 2 satellites collected by the global tracking network of about 40 stations. Now five analysis centers submit operational (with 2–15 days delay) solutions and about ten analysis centers contribute yearly final (up to 23 years) ERP series. Some statistics related to SLR observations and analysis are presented and analyzed. Possible problems in SLR observations and analysis and ways of its solution are discussed.
Anomalous Roughness of the Pole Path at the Time of the 1994 Bolivia and Kurile Islands Earthquakes
Authors: Spada G. , Alfonsi L. , Soldati G. 
Published: July 2016

AbstractWe report anomalies in the roughness of the path of the pole of rotation at the time of the Bolivia earthquake of June 9, 1994 (Mω = 8.2) and of the Kurile Islands earthquake of October, 4, 1994 (Mω = 8.3). This finding reinforces the results of previous studies, which have indicated changes in the polar motion curvature at the time of major earthquakes.
Excitation of Polar Motion
Authors: Wilson Clark R. 
Published: July 2016

AbstractConceptual models of polar motion have evolved over the past century, as improved data revealed signals over progressively wider frequency bands. In the 1890s, Chandler represented polar motion as a sum of discrete components, 14 month and annual terms, and this component model effectively summarized the observations, but did not provide a physical explanation for them. Over time both the search for a physical understanding of polar motion, and the ability to observe the broad band continuum outside the Chandler and annual bands have led to an understanding of polar motion as a continuum of variations, not adequately described by a few discrete components. The continuum concept is now the working model in most studies of polar motion. The transition from component to continuum conceptual models preceded the arrival of high quality data by several decades, and reflected significant contributions from Harold Jeffreys. With modern space geodetic observations and good global numerical models of the atmosphere, oceans, and other climate processes, it is clear that air and water motion and redistribution are the dominant contributors to the excitation continuum.
Study of the Regime of the Polar Motion by Means of Numerical Method
Authors: Rykhlova L. , Kurbasova G. 
Published: July 2016

AbstractAnalysis of the spectral power-density function and the Poincaré method are used to identify the type of motion exhibited by the Earth’s pole from 1900–1990. The former method allows identification of a quasi-periodic regime with two main frequencies — annual and Chandler. The existence of combinational frequencies in this spectrum and the broadening of the spectral peaks suggest a quasi-periodic regime making a transition to chaos. It is concluded that the identification of the polar motion regime over the time interval considered is insufficient to predict the further evolution of the system over arbitrarily long times.
Short-Period Oscillations of Earth Rotation
Authors: Kołaczek B. , Kosek W. , Schuh H. 
Published: July 2016

AbstractSub-seasonal variations and especially sub-seasonal oscillations with periods of about 120, 60, 50, 40 days in polar motion and of about 120, 60–90, and 50 days in LOD are presented. Variations of amplitudes of these sub-seasonal oscillations of polar motion are shown. Maxima of these amplitudes are of the order of 2–4 mas. These oscillations are elliptical ones. The correlation coefficients between geodetic and atmospheric excitation functions in this range of the spectrum are variable and have annual variations. Maxima of correlation coefficients are of the order of 0.6–0.8.Modern geodetic VLBI experiments provide very accurate results in polar motion and UT1–UTC with a temporal resolution of 3–7 minutes. Several irregular, quasi-periodic variations were found. In many UT1–UTC data sets, oscillations with periods around 8 hours and between 5 and 7 hours can be seen.
Comparison of the Short Period Rigid Earth Nutation Series
Authors: Bizouard Ch. , Folgueira M. , Souchay J. 
Published: July 2016

AbstractWe present a comparison of the diurnal and subdiurnal nutations of the three last theories of rigid Earth nutation: SMART97, RDAN97 and REN 2000. For a better interpretation of the observations, we characterize their contribution to the polar motion and we estimate the nonrigid effects.
Advanced Observations of Lunar Physical Librations and Gravitational Fields in Japanese Lunar Missions in the Near Future
Authors: Hanada Hideo , Heki Kosuke , Kawano Nobuyuki , Ooe Masatugu , Tsubokawa Tsuneya , Tsuruta Seiitsu , Ishikawa Toshiaki , Araki Hiroshi , Matsumoto Koji , Takanezawa Takashi , Kono Yusuke , Karoji Hiroshi , Iwata Takahiro , Kaneko Yutaka , Yokoyama Takaaki 
Published: July 2016

AbstractIn the SELenological and ENgineering Explorer (SELENE) project which is the Japanese lunar program to be launched in 2003 by the Institute of Space and Astronautical Science (ISAS) and National Space Development Agency of Japan (NASDA), we measure angular distance between a radio transmitter on a relay satellite, that on the Moon and quasars by differential VLBI and determine amplitudes of the physical librations, gravitational harmonic coefficients of the Moon and lunar ephemeris with an accuracy one or two orders higher than before in cooperation with 4-way Doppler measurements and two-way Doppler and ranging measurements using the lunar orbiter and the relay satellite. We are proposing another selenodetic mission, In situ Lunar Orientation Measurement (ILOM) to study lunar rotational dynamics by direct observations of the lunar physical libration from the lunar surface with an accuracy of 1 milliarcsecond in a post-SELENE project which will be launched about three years after SELENE. Year-long trajectories of the stars provide information on various components of the physical librations and we will also try to detect the lunar free librations in order to investigate the lunar mantle and the liquid core.
Non-Radial Oscillations of Degenerate Dwarfs: A Theoretical Review
Authors: Van Horn H.M. 
Published: July 2016

AbstractThe current status of the theory of non-radial oscillations of white dwarfs and hydrogen shel1-burning degenerate stars, in the linear, quasi-adiabatic approximation, is reviewed. Relevant aspects of the thermal structure of such stars are summarized, and several problem areas requiring further investigation are identified. Among the most interesting and important of these are the question of the existence of g modes in white dwarfs; the nature of the excitation mechanisms for non-radial oscillations; the possibility of tidal excitation; the problem of mode-coupling between pulsations and convection; and the question of the effects of a solid, crystallizing core.
Planetary Theories and Observational Data
Authors: Duncombe R. L. , Seidelmann P. K. 
Published: July 2016

AbstractA brief review is given of planetary theories from Leverrier to Newcomb to the age of computers. The presently used planetary theories are discussed and the process of replacing these theories with new ones is described. Some difficulties in preparing new planetary theories and the observational discrepancies which have been encountered previously are discussed.
Qualitative Dynamics of the Sun-Jupiter-Saturn System
Authors: Szebehely V. 
Published: July 2016

AbstractThe stability of the three-body problem formed by the Sun, Jupiter and Saturn is investigated using surfaces of zero velocity. The results obtained with the models of the restricted and general problems of three bodies are compared with numerical integration. The system is found to be stable in the sense that Saturn will neither interrupt the (perturbed) binary orbit of Jupiter around the Sun, nor will it escape from the system. It is shown that the known classical triple stellar systems are “more stable” than the solar system, which in turn is “more stable” than the Earth-Moon system.
A New Approach for the Construction of Long-Periodic Perturbations
Authors: Dvorak Rudolf 
Published: July 2016

AbstractThe aim of this work is to study perturbations of planets of a period of some thousands of years. The use of an analytical method allows us to separate all different influences, e.g. near resonances and is combined with the very precise method of the numerical integration. The truncation to low orders can be avoided which is made by analytical methods in using developments with respect to the small parameters inclinations and eccentricities. For this purpose a special form of the Lagrange Equations is used where the terms containing the inverse distancefrom the planet to the perturbing one are separated as it is the most difficult to compute. To develop this a specific formulation has been found where the short periodic terms can precisely be determined. Although the development seems to be of a certain complexity the small numbers of quantities used can be tabulated once and for all in a specific problem. It should be possible to integrate the new form of the Lagrange Equations within a reasonable computer-time to determine the long periodic perturbations.
Relation of a Contracting Earth to the Apparent Accelerations of the Sun and Moon
Authors: Lyttleton R.A. 
Published: July 2016

AbstractThe tidal theory of the evolution of the lunar orbit has remained inconsistent with the observational values of the apparent secular accelerations of the Sun and Moon since it was first developed by Jeffreys in 1920. Allowance for a changing moment of inertia of the Earth enables the discrepancy to be completely removed if a decrease is occurring at a rate of just about the amount already required by the phase-change theory of the nature of the terrestrial core. The agreement of the resulting theory with the latest determinations of the lunar acceleration increases confidence in the phase-change hypothesis. On the other hand the theory renders it most unlikely that a changing constant of gravitation will prove necessary to account for the observations. On the present theory of itself the Moon would have been extremely close to the Earth only about 109 years ago which suggests that some additional process may at times have influenced the lunar orbit.
Comets and the Missing Planet
Authors: Ovenden Michael W. , Byl John 
Published: July 2016

AbstractIntegrating backwards in time in the circular restricted three-body problem Galaxy-Sun-Comet, for both the real long-period comets and fictitious random sets of orbital elements, we have confirmed van Flandern’s conclusion that there is a statistically-significant clustering of the orbits of real long-period comets, in heliocentric direction, some 5×106 years ago. The clustering is also significant in heliocentric distance, and is more marked if it is assumed that the comets have gone round the Sun more than once since the epoch of maximum clustering. We suggest that the “event” discovered by van Flandern is not the explosive disruption of a planet formerly in the asteroid belt, but the latest in a series of minor catastrophies, such as the collisional break-up of a pair of large asteroids.
Hamiltonian Theory of the Libration of the Moon
Authors: Henrard Jacques , Moons Michèle 
Published: July 2016

AbstractThe feasibility of applying the Lie transform method to the problem of the physical libration of the Moon is investigated. By a succession of canonical transformations, the Hamiltonian of the problem is brought under a form suitable for perturbation technique. The mean value of the inclination of the angular momentum upon the ecliptic and the frequencies of the free libration are computed.
Numerical Integration of Nearly-Hamiltonian Systems
Authors: Bond Victor R. 
Published: July 2016

AbstractConsideration is given to the solution by numerical integration of systems of differential equations that are derived from a Hamiltonian function in the extended phase space plus additional forces not included in the Hamiltonian (that is, nearly-Hamiltonian systems). An extended phase space Hamiltonian which vanishes initially will vanish on any solution of the system differential equations. Furthermore, it vanishes in spite of the additional forces, and defines a surface in the extended phase space upon which the solution is constrained.
Theory of Motion of Jupiter’s Galilean Satellites
Authors: Lieske J.H. 
Published: July 2016

AbstractThe final results for the theory enabling one to calculate the positions of the Galilean satellites and their partial derivatives are presented, following the techniques outlined in earlier papers. Extensive use of algebraic manipulation software on a digital computer is employed to generate the final expressions. The new theory is, in effect, a revitalization of Sampson’s theory in which we (a) remove algebraic and mathematical errors existing in Sampson’s work, (b) introduce some neglected effects due to solar interactions and the 3-7 commensurability, (c) allow for non-zero amplitude and phase of the free libration, (d) express the final results as analytic functions of variations in 49 arbitrary constants of integration and physical parameters, (e) construct the theory in a manner which readily allows for future revision, and (f) provide analytic expressions for the partial derivatives with respect to the 49 parameters.
Perturbations of Critical Mass in the Restricted Three-Body Problem
Authors: Sharma R.K. , Subba Rao P.V. 
Published: July 2016

AbstractBased upon the authors’ result (Astron. Astrophys. 43, 331-3, 1975) that oblateness of the more massive primary decreases the value of the critical mass, this note is concerned primarily with a few observations on Szebehely’s result (Astron. J. 72, 7-9, 1967) that the Coriolis force is a stabilizing force. It has been deduced that a small change ε in the Coriolis force from unity results in a perturbation of the critical mass by a factor of -8ε/81.
Model Atmospheres with Periodic Shocks
Authors: Bowen G. H. 
Published: July 2016

AbstractThe pulsation of a long-period variable star generates shock waves which dramatically affect the structure of the star's atmosphere and produce conditions that lead to rapid mass loss. Numerical modeling of atmospheres with periodic shocks is being pursued to increase our understanding of the processes involved and of the evolutionary consequences for the stars. It is characteristic of these complex dynamical systems that most effects result from the interaction of various time-dependent processes. For example, rapid mass loss in the models is a joint consequence of the enormous extension of the atmosphere caused by shocks, and of radiation pressure on grains formed in the cool outer region; it is also affected by thermal relaxation processes, which determine the temperature distribution. The progress and significance of these modeling calculations will be reviewed.
Evolution of Oxygen-rich and Carbon Stars on the Asymptotic Giant Branch
Authors: Kwok Sun , Volk Kevin M. , Chan S. Josephine 
Published: July 2016

For many years, it has been commonly believed that oxygen-rich (M) stars evolve first to S stars and then to carbon (C) stars. However, the details of the transition are not understood. It is now accepted that the overabundance of carbon ([C/O] > 1) in some asymptotic giant branch (AGB) stars is due to the dredge up of products of a capture and s-process elements after a number of thermal pulses (Iben 1975). Effects of convective overshooting and semiconvection in the dredge up process have also been considered (Castellani et al. 1985, Lattanzio 1986). The dredge up of carbon into the photosphere leads to the formation of carbon-based molecules, which absorption bands become the basis of spectral classification.During the past decade, it is recognized that the carbon-richness of a star not only manifests itself in the photospheric spectrum, but also in the circumstellar environment as well. Probes of the circumstellar envelopes in the infrared and radio regions provide new means to characterize the chemical properties of the star. These methods are particularly useful in cases where the photosphere is heavily obscured by circumstellar absorption. Table 1 summarizes the photospheric and circumstellar spectral characteristics of M and C stars.
Report of the IAU Working Group on the Theory of Nutation
Authors: McCarthy Dennis D. 
Published: July 2016

AbstractModern observations of celestial pole offsets indicate that small but significant corrections to the current IAU theories of nutation and precession can be detected. These corrections are of the order of a few milliseconds of arc. To meet the needs of those who require millisecond of arc accuracy in reference frame applications, the International Earth Rotation Service (IERS) publishes in weekly and monthly bulletins the most recent observations, along with predictions of these corrections. These appear to meet the needs of users. In view of the fact that the geophysical community has not adopted a model which describes the nutation and precession theory and that the current procedure of the IERS meets the need of high-accuracy users, there does not appear to be a need to identify a new IAU nutation theory at this time.
Observations of the Planetary Satellites Europa and Titan by Hipparcos
Authors: Arlot J.-E. , Bec-Borsenberger A. , Dourneau G. 
Published: July 2016

AbstractObservations of the satellites Europa and Titan will be obtained from the European Astrometric Satellite HIPPARCOS. These observations will be used to obtain “observed” positions of the planets Jupiter and Saturn; these positions have the advantages, first to be given in the reference frame defined by the Hipparcos system, and second, the accuracy on these positions is better than the accuracy of the ground-based observations of these planets. To obtain the positions of the planets from those of their satellites, we have to take the calculated positions of these satellites by means of their ephemerides. The accuracy of the computed positions of Europa and Titan relatively to their primary is of the order of 0ʺ.l, better than the one of the direct observation of Jupiter and Saturn. An efficient comparison of the different ephemerides of these planets will be possible that way.
Photographic Catalogue of 200000 Southern Stars – FOCAT–S
Authors: Bystrov N.F. , Polojentsev D.D. , Potter H.I. , Yagudin L.I. , Zalles R.F. , Zelaya J.A. 
Published: July 2016

AbstractThe catalogue of about 200000 stars in the zone from equator to southern pole was complied from photographic observations carried out during 1982 – 1969 years in USSR and Bolivia by Pulkovo astrograph (D=23 sm, F=230 sm, working field 4° × 4° ). The plates were measured by Zeiss Ascoreoord measuring mashines in Pulkovo, Tarija, and others observatories. The process of measurement and compilation of catalogue were carried out in Pulkovo by ES–1033 computer. The observations were made with a four–fold overlap of the sky. Reference oatalogue is SRS catalogue (FK5 system). The differencial refraction, differencial aberration and objective distortion were taken into account. The mean accuracy of catalogue FOCAT-S positions is ±0.123″.
Internal Precision in CCD Astrometry of QSO Optical Counterparts
Authors: Chiumiento G. , Lanteri L. , Lattanzio M.G. , Massone G. 
Published: July 2016

AbstractThe main purpose of this contribution is twofold. First, we report on a preliminary assessment of the astrometric properties of the CCD system we are presently using to extend the magnitude limit of the Torino program on optical positions of QSO’s. This assessment is based on the internal consistency of the positions derived from different CCD frames of the same objects. Then, we give a first evaluation of the precision of CCD derived QSO positions after extending a plate based reference frame (secondary frame) onto the CCD images (tertiary frame).Special emphasis is given to comparisons with plate positions of the same faint objects. It is shown that use of the CCD camera promises a factor of five (or larger) improvement in the precision of QSO positions.
Influence of Systematic Differences of FK4 on Determining Earth Orientation Parameters
Authors: Wenjing Jin , Tongqi Xu , Peizhen Lu , Dechun Liao 
Published: July 2016

AbstractIn this paper the corrections of positions and proper motions (J2000) of FK4 were obtained. For different kinds of observational methods the formulae of calculating the influence of systematic differences of FK4 on time and latitude determinations were derived. The influence of systematic differences on the universal time and polar coordinates (1980–1988) of Chinese Joint System (CJS) and the global optical solution of earth orientation parameters (1987–1988) were calculated and their external precisions referred to BIH or IERS were also re–estimated.
Observations of Luni-Solar and Free Core Nutation
Authors: McCarthy Dennis D. , Luzum Brian J. 
Published: July 2016

AbstractAn analysis of the differences between observed nutation angles and the 1980 IAU Nutation Theory shows the existence of currently unmodeled effects. An empirical set of corrections to the 1980 IAU Nutation Theory is presented and compared with current geophysical models. A prograde periodic variation (period ≈ 420 days), which may be related to the theoretical free core nutation, is apparently seen.
The Extragalactic Reference Frame
Authors: McCarthy Dennis D. , Russell Jane , Archinal Brent , Carter Merri Sue , Florkowsi Dave , Holdenried Ellis , Johnston Ken , Yao Zhen-Guo 
Published: July 2016

AbstractA cooperative program has been established to produce a reference frame of at least 400 suitable extragalactic sources. This is an extension of collaborative efforts (Johnston et al., Russell et al., Ma et al., and Reynolds et al.) reported at this meeting. In Phase One, a catalog of radio source positions will be constructed using original VLBI observations already obtained by NASA, NGS, NRL, JPL and USNO. Observations will be re-reduced in a consistent system to avoid some of the more serious problems associated with the formation of compilation catalogs. In Phase Two, the USNO will maintain the system, including the monitoring of source structure and/or variation. During both phases cooperation among the various agencies will continue. A list of sources will be made available to optical observers so that the frame will have benchmarks in both the optical and radio regimes.
Analysis and Synthesis of Catalogues of Extragalactic Radio Sources
Authors: Walter H.G. 
Published: July 2016

AbstractRecent observation catalogues of extragalactic radio sources obtained by Very Long Baseline Interferometry agree in the mean to a few milliarcseconds (mas). Within this range the position differences show constant, linear and periodic offsets. To cast light on these offsets the differences between some of the representative observation catalogues are plotted. Especially, the periodic variations of declination differences of observation catalogues having significantly different epochs are tentatively explained by an uncertainty of the general precession in declination. In terms of the luni-solar precession this uncertainty is estimated to be of the order of −1to −2 mas per year.