bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regular and Chaotic Motion in Globular Clusters
Authors: Carpintero Daniel D. , Muzzio Juan C. , Wachlin Felipe C. 
Published: July 2016

AbstractAs a first step towards a comprehensive investigation of stellar motions within globular clusters, we present here the results of a study of stellar orbits in a mildly triaxial globular cluster that follows a circular orbit inside a galaxy. The stellar orbits were classified using the frequency analysis code of Carpintero and Aguilar and, as a check, the Liapunov characteristic exponents were also computed in some cases.The orbit families were obtained using different start spaces. Chaotic orbits turn out to be very common and while, as could be expected, they are particularly abundant in the outer parts of the cluster, they are still significant in the innermost regions. Their relevance for the structure of the cluster is discussed.
Periodic Orbits Around a Massive Straight Segment
Authors: Riaguas Andrés , Elipe Antonio , Lara Martín 
Published: July 2016

AbstractIn this paper, we consider the motion of a particle under the gravitational field of a massive straight segment. This model is used as an approximation to the gravitational field of irregular shaped bodies, such as asteroids, comet nuclei and planets’s moons. For tbis potential, we find several families of periodic orbits and bifurcations.
Canonical Variables of The Second Kind and The Reduction of The N-Body Problem
Authors: Bryant John G. 
Published: July 2016

AbstractWe introduce a new kind of canonical variables that prove very useful when the order of a Hamiltonian system can be reduced by one, as in the case of isoenergetic reduction, and of what we call homogeneous reduction. The Kepler Problem, Geometrical Optics and McGehee Blow-up are discussed as examples. Finally we carry out the isoenergetic reduction of the general N-Body Problem using the new variables, and briefly discuss its application to the problem of collision.
The Hamiltonian Dynamics of The Two Gyrostats Problem
Authors: Mondejar F. , Vigueras A. 
Published: July 2016

AbstractThe problem of two gyrostats in a central force field is considered. We prove that the Newton-Euler equations of motion are Hamiltonian with respect to a certain non-canonical structure. The system posseses symmetries. Using them we perform the reduction of the number of degrees of freedom. We show that at every stage of the reduction process, equations of motion are Hamiltonian and give explicit forms corresponding to non-canonical Poissson brackets. Finally, we study the case where one of the gyrostats has null gyrostatic momentum and we study the zero and the second order approximation, showing that all equilibria are unstable in the zero order approximation.
The Effect of C22 on Orbit Energy and Angular Momentum
Authors: Scheeres D.J. 
Published: July 2016

AbstractThe effect of the C22 gravity field term on a particle is evaluated analytically over one orbit to find the change in orbit energy and angular momentum as an explicit function of the orbital inclination, argument of pericenter, longitude of the ascending node, orbit parameter and eccentricity. Changes in orbit energy and angular momentum are shown to be proportional to a family of integrals which can be parameterized in terms of eccentricity and non-dimensional pericenter radius.
The Use of Lie Series in The Construction of a Perturbation Theory and some Recent Results in The Theory of The Motion ofd Hyperion
Authors: Message P.J. 
Published: July 2016

AbstractThis paper begins with a brief review of a form of the Lie series transformation, and then reports some new results in the study, using Lie series methods, of the orbit of Saturn’s satellite Hyperion. In particular, improved expressions are given for the long-period perturbations of the orbital elements which describe the motion in the orbit plane, and also first results for expressions for the short-period perturbations in the apse longitude, derived from the Lie series generating function.
The Asteroid Mass Determination Project at The U.S. Naval Observatory
Authors: Hilton James L. , Stone Ronald C. 
Published: July 2016

Asteroid masses are the largest source of unmodeled forces in current planetary ephemerides research. Williams (1984) showed that the asteroids produce km size perturbations in the position of Mars. However, the masses of only three asteroids are known to better than 10%, and only six other asteroid masses have been determined at all.Detecting the mass of an asteroid is difficult because the observed quantity is the change in the mean motion of a second, perturbed asteroid. Asteroid masses are small, so the change in the mean motion is typically on the order of 0."015 yr−1. Thus, excellent orbit determinations are needed both before and after the perturbing encounter. This requires high precision observations over as many oppositions as possible.Hilton (1997) determined the mass of 15 Eunomia to within 25% by detecting perturbations of 1313 Berna. The greatest source of uncertainty in determining the mass of Eunomia was the very poor coverage and accuracy of pre-encounter observations. Hilton (1998) has determined the masses of 1 Ceres, 2 Pallas and 4 Vesta, all based on mutual interactions. The uncertainties in the masses are 1% for Ceres, 3% for Pallas, and 7% for Vesta. The masses of Ceres and Pallas are the best so far, and the mass for Vesta corroborates previous determinations of its mass.
The Asteroid Identification Problem
Authors: Sansaturio M.E. , Milani Andrea , La Spina A. 
Published: July 2016

A large fraction of the asteroids observed so far are to be considered lost, that is they cannot be recovered by pointing the telescope at the predicted position only. The catalogues of asteroid orbits are therefore polluted by large numbers of low accuracy orbits, which cannot be easily improved by observation. Two of these inaccurate orbits can belong to the same physical object, and indeed identifications are regularly found when the orbital elements are close; an unknown number of real identifications have not been found in the existing catalogues because the orbital elements as computed are far apart. It is impossible to systematically check for possible identification of all the couples of orbital element sets; an algorithm is required to single out a comparatively small number of proposed identifications, and to find a suitable first guess within the region of convergence of the differential corrections procedure to be used to confirm the identification.In the linear approximation the target function to be minimized is a quadratic form; thus a fully analytic algorithm can be given to compute both the first guess for an identification and the cost, that is the increase in the target function resulting from joining the two sets of observations. This allows to define a number of distances in the elements space, which are functions, not only of the two orbital element sets, but also of their uncertainties, as measured by the Gaussian covariance matrices. Tests on the values of these distances are used as preliminary filters, to allow more extensive computations to be performed on a fraction of the total number of possible couples.
Target Plane Confidence Boundaries: Mathematics of The 1997 XF11 Scare
Authors: Milani Andrea , Valsecchi Giovanni B. 
Published: July 2016

The uncertainty of the close approach distance of a Potentially Hazardous Object (PHO), either an asteroid or a comet, can be represented on the Modified Target Plane (MTP), a modification of the one used by Öpik. The MTP is orthogonal to the geocentric velocity at the closest approach along the nominal orbit, solution of the least square fit to the observations. The confidence regions of this solution in the 6-D space of orbital elements (for an epoch close to the observations) are well approximated by a family of concentric ellipsoids, if the observed arc is not too short. In the linear approximation these ellipsoids are mapped on the MTP into concentric ellipses, which can be computed by solving for the state transition matrix.For a PHO observed at only one opposition, with a close approach expected after many revolutions, the ellipses on the MTP become extremely elongated and the linear approximation may fail. In this case the confidence boundaries on the MTP, i.e. the nonlinear images of the confidence ellipsoids, may not be well approximated by the ellipses. The Monte Carlo method (Muinonen and Bowell, 1993) can be used to find nonlinear confidence regions, but the computational load is very heavy: to estimate a low probability event the number of test cases must be larger than the inverse of the probability. We propose a new method to compute semilinear confidence boundaries on the MTP (Milani and Valsecchi, 1998), based on the theory developed to compute confidence boundaries for predicted observations (Milani, 1999). This method is a good compromise between reliability and computational load, and can be used for real time risk assessment.
Periodic Orbits in Three-Armed Galaxies
Authors: Grosbøl Preben J. , Patsis Panos A. 
Published: July 2016

Although interarm features in the Population I disk of spiral galaxies frequently give an impression of a three-fold symmetry (Patsis et al., 1997), true three-armed spiral structures in the old stellar disk are seldomly seen. Such systems are of special interest since they display unique conditions which favor the growth of m=3 modes. The face-on spiral NGC 7137 shows a clear three-armed pattern on K-band images and was used as a prototype for the potential of these systems.A K-band map of NGC 7137 was decomposed in axisymmetric components and a synthetic rotation curve was generated [see (Grosbøl and Patsis, 1998)]. The maximum rotational velocity was taken to be ≈150 km sec−1 corresponding to the mean value given by (Rubin et al., 1982) for this type of galaxy.
Second Order Perturbations of Elliptic Elements with Respect to the Initial Ones
Authors: Marco Castillo F.J. , Martínez Usó M.J. , López Ortí J.A. 
Published: July 2016

AbstractThe following paper is devoted to the theoretical exposition of the obtention of second order perturbations of elliptic elements and is a follow-up of previous papers (Marco et al., 1996; Marco et al., 1997) where the hypothesis was made that the matrix of the partial derivatives of the orbital elements with respect to the initial ones is the identity matrix at the initial instant only. So, we must compute them through the integration of Lagrange planetary equations and their partial derivatives.Such developments have been applied to the individual corrections of orbits together with the correction of the reference system through the minimization of a quadratic form obtained from the linearized residual. In this state two new targets emerged:
1.To be sure that the most suitable quadratic form was to be considered.2.To provide a wider vision of the behavior of the different orbital parameters in time.Both aims may be accomplished through the consideration of the second order partial derivatives of the elliptic orbital elements with respect to the initial ones.
Changing Periods of Long-Period Variables
Authors: Hoffleit Dorrit 
Published: July 2016

AbstractA manuscript catalogue has been prepared listing all of the Mira-type and SRa variables reputed at one time or another to have changing periods (356 stars). The frequencies of the recorded changes are investigated and qualitatively discussed. For a selected list of 100 of these stars (Table III) the published JD0of maximum for successive time-intervals are examined to see if they cannot better be represented by constant periods. Such data are suggestive but inadequate for definitive conclusions. For many of these stars the AAVSO has accumulated observations spanning over one hundred years. Sophisticated analyses of these rich data are to be encouraged.
Polarimetric Observations of Red Variables: A Study of Gas and Particle Interactions
Authors: Coyne G. V. , McLean I. S. 
Published: July 2016

AbstractIn recent years the wavelength, dependence of the polarization in a number of Mira variables, semi-regular variables and red supergiants has been measured with resolutions between 0.3 and 300 A over the range 3300 to 11000 A. Variations are seen across molecular absorption bands, especially TiO bands, and across atomic absorption and emission lines, especially the Balmer lines. In most cases one can ignore or it is possible to eliminate the effects due to interstellar polarization, so that one can study the polarization mechanisms operating in the stellar atmosphere and environment. The stars Omicron Ceti. (Mira), V CVn (semi-regular variable) and Mu Cephei (M2 la), in addition to other stars similar to them, will be discussed in some detail.Models to explain the observed polarization consider that the continuum flux is polarized either by electron, molecular and/or grain scattering or by temperature variations and/or geometrical asymmetries over the stellar photosphere. This polarized radiation is affected by atomic and molecular absorption and emission processes at various geometric depths in the stellar atmosphere and envelope. High resolution spectropolarimetry promises, therefore, to be a power-rul tool for studying stratification effects in these stars.
Variable Star Research at Los Alamos
Authors: Davis C. G. , Cox A. N. , Adams T. F. 
Published: July 2016

AbstractWe are at present engaged in three major areas of variable star research at Los Alamos: 1) A study using improved Cepheid light curves in order to define more precisely the Hertzsprung sequence, in collaboration with John Castor and John Cox, 2) The suggestion by A. Cox that helium enrichment occurs in the stellar envelope, by a stellar wind, which may explain many of the mass anomalies, this work being with G. Michaud, D. King, R. Deupree, and S. Hodson, and 3) The study of Cepheid and RR Lyrae colors to compare directly to the observations. A brief discussion of the present status of each of these research programs will be given.
Trigonometric stellar parallaxes
Authors: Strand K. Aa. 
Published: July 2016

I derive some satisfaction from the fact that the general judgment of astrometric work with reflectors as being inferior to that carried out with the long focus refractors, which existed for most of this century, is no longer generally accepted, and that the USNO 61-inch astrometric reflector has contributed to this.If, however, van Maanen had continued his parallax work with the 60-inch Mt. Wilson reflector, or stayed within the small coma free field of the 100-inch telescope, his contributions to the parallax field would have been more justly appreciated.
On possible improvment of fundamental star coordinate system using radiointerferometric and photographic Quasar observations
Authors: Gubanov V. S. , Kumkova I.I. 
Published: July 2016

At present the astrometry possesses the new perspective measuring method namely very long baseline interferometry (VLBl).Possibility of establishing inertial (unrotating) radio source coordinate system (IRCS) is one of VLBI technique advantages. This system may be useful as a reference system for studying of a wide range of geodynamic, ce -lestial mechanic, geophysic, navigational and other applied astrometry problems.
On the astrometric performance of the 60 inch L. Figl Telescope and results from a joint program of precise optical positions of radio sources in the FK4 System
Authors: Vegt Chr. de , Prochazka F. V. 
Published: July 2016

The 60” R.C.Telescope of the Vienna University Observatory is located at the Schöpfl which is situated about 30 km west from Vienna in a height of about 900 m.Fig.1 gives the optical data of the 60”.
Current results and developments in astrometric VLBI at the Jet Propulsion Laboratory
Authors: Purcell G. H. , Cohen E. J. , Fanselow J. L. , Rogstad D. H. , Skjerve L. J. , Spitzmesser D. J. , Thomas J. B. 
Published: July 2016

AbstractThe Jet Propulsion Laboratory is engaged in a program of astrometric VLBI as one element of a navigation system for interplanetary spacecraft. The program involves stations of the Deep Space Network in Spain, the United States, and Australia, and is now in an advanced stage of development.As one part of this program we are developing a radioastrometric source catalog which at present contains about fifty sources with positions known to better than 0.”05. Our results agree well with those published by other groups.We are continuing to refine our delay model, and we are improving our data reduction procedures to account better for the effects of instrumental and ionospheric delays. When the system becomes fully operational in July of 1979, we expect the catalog to contain at least a hundred sources with positions accurate to 0.”01.
Thermal and aerodynamical analysis of a meridian building
Authors: Hog E. 
Published: July 2016

AbstractOn a night with low wind speed, the refraction inside a conventional meridian dome can cause a systematic error about 0.”2. In view of the recent improvements of meridian techniques through photoelectric micrometers it is desirable to reduce also this remaining source of error. The present study gives a quantitative theory of the astrometric effect of insulation and ventilation of a meridian building, both for the closed and the open dome, and for daytime as well as for the night. The conclusions are formulated so that they can easily be applied to the design of new buildings and to improvement of existing ones. The design differs from current practice in that e.g. the basement should be well ventilated; the piers must therefore be insulated also in the basement. It is concluded that the slit width is not critical and that a rather narrow slit is therefore altogether preferable, quite opposite to the popular opinion that the roof ought to be completely removed during observation.A building constructed according to these principles, including a slit of 1.4 m width, would have about 5 times smaller thermal effects than the present one in Brorfelde.It would be interesting and simple to extend the methods and results to other astronomical domes in order to diminish seeing effects.
A comparative study of trigonometric parallax reduction techniques
Authors: Russell J. L. 
Published: July 2016

Trigonometric parallaxes from measurements of photographic plates have always been reduced by some variant of the method of plate constants. From the dependences technique developed by Schlesinger (1910) to the full rigorous non-iterative approach, to be discussed below, all methods depend on the basic equationsto represent the relationship between a star’s standard coordinates (ξ, η) in the sky and its cartesian coordinates (x, y) obtained from measurements of a photographic plate. The quantities A through F are the plate constants. Besides allowing for the necessary affine transformation, these terms remove the first order effects of refraction, aberration, seeing, etc. Individual instruments may need additional terms on the right-hand side of eqs. (1) to account for errors introduced by the optical system.
Progress in the compilation of the FK5
Authors: Fricke W. , Gliese W. 
Published: July 2016

Abstract:Presented is a status report on work on FK5 giving information on the following items: (a) the intended increase of the number of fundamental stars and their magnitude range in FK5, (b) available material for the improvement of the system, (c) methods for the determination of systematic differences, (d) the determination of equator and equinox of FK5, and (e) the elimination of the motion of the FK4 equinox.
Final results of relative declination observations made with the Repsold Meridian Circle at Cerro Calan
Authors: Carrasco G. 
Published: July 2016

Abstract:The final results of 1936 individual observations in declination of stars of the FK4 Catalogue along the whole meridian arc and 18583 individual observation of stars from the International Programme SRS and BS and FK4 in the declination zone -20° to -40° are given.The systematic differences Δδδand Δδαand the comparison with other catalogues is presented too.
The contribution of Hipparcos to the study of open clusters
Authors: Feissel M. , Gómez A. 
Published: July 2016

The observation by the projected ESA astrometric satellite Hipparcos (HIghPrecisionPARallaxesCOllectingSatellite) of stars in nearby open clusters is studied and the expected precision and accuracy of their parallax measurements are evaluated. The amplitude of local systematic errors will certainly be smaller than the precision of the results, a feature which is very seldom realized in global astrometric sets of data; this will have far-reaching consequences.With the exception of Hyades, these measures will be the first trigonometric parallaxes ever obtained for open clusters. The precision of astronomical interferences from clusters properties will be greatly improved.
Image Reconstruction from VLBI Amplitude and Phase Closure Data
Authors: Cotton William D. , Wittels Jill J. 
Published: July 2016

AbstractA two step procedure is developed for the determination of the angular structure of the compact components of radio sources from observations made with very long baseline interferometry (VLBI). The first step is to fit a model composed of circularly symmetric Gaussian components to the observations. Then this, or any other, model and closure phase information is used to predict visibility phases which, when paired with the corresponding visibility amplitude observation, are combined in a direct synthesis; the resulting map is deconvolved from the point source response by means of the “CLEAN” procedure. If necessary, the “cleaned” components can be used as a starting model to predict visibility phases and the process iterated. The initial model in many cases may be as simple as a point source. Convergence of this process appears to be quite rapid, requiring only a few iterations when the source is simple or the starting model is good. These two steps for source mapping can be used either together or separately. Examples are given using data generated from test models.
An Acousto-optical Image Processor and Its Application to a 160 MHz Interferometer
Authors: Kai Keizo , Kosugi Takeo 
Published: July 2016

AbstractRadio emissions from the Sun are characterized by extremely rapid time variation. Although they are relatively strong, the signal to noise ratio becomes critical when we observe them with high resolution in space and time. To improve the S-N ratio, we have investigated the feasibility of an acousto-optical processing of interferometer images and applied it to the 160 MHz interferometer of the Nobeyama Solar Radio Observatory. We present here results of simulation experiments and preliminary solar observations with the new image processor.