CORRELATED FLUCTUATING SIGNALS IN THE ANALYSIS OF THE LARGE SCALE STRUCTURE OF THE UNIVERSE
DORU MARIAN SURAN, NEDELIA ANTONIA POPESCU
Astronomical Institute of the Romanian Academy,
75212 Bucharest 28, Romania
Abstract.Recent observations of the Large Scale Structure of the Universe suggest inhomogeneities on a scale larger than previously thought. Our previous results (Surqn 1991) indicated that the signals of the inhomogeneities in different 3D catalogs ( galaxies, clusters, superclusters) are correlated, suggesting the presence of phase fluctuations in the long tail of the correlation function (§(r) for r > rg). The results are in good agreement with BEKS (1990, 1991; 1D pencil beams techniques). The comparison with different 3D simulations is made in order to derive the cosmological texture of the Universe on a scale lerger than 20 MPC. Also the comparison with the simulated power spectrum is made in order to derive the transition function Tf (k) for the intermediate scale (100h-¹
Mpc< r < 1000 h-¹ Mpc)
Key words: Large Scale Structure of the Universe- texture; cosmology - correlation function, transfer function.
GRAVITATONAL ENERGY FOR A CLASS OF RELATIVISTIC STELLAR MODELS
VASILE URECHE
University of Cluj-Napoca, Faculty of Mathematics,
Str. M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania
TIBERIU OPROIU
Astronomical Institute of the Romanian Academy, Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. The paper deals with the determination of the gravitational energy at barotopic stellar
models in a relativistic approximaion. The way to calculate the gravitational packing coefficient is shown. The numerical estimates are tabulated and plotted. One can conclude that the gravitational energy represents a significant part of the total stellar energy.
Key words: relativistic stars - barotropic models - gravitational energy.
GABRIELA OPRESCU , DORU MARIAN SURAN
Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint No. 5, 75212 Bucharest 28, Romania
Abstract. UBV light curves for AW Cam are obtained at Bucharest Observatory. Light Curves solutions are presented.
Key words: eclipsing binaries - AW Cam photometry, elements.
REMARKS ON THE APSIDAL MOTION OF TX URSAE MAJORIS
IOAN TODORAN and RODICA ROMAN
Astronomical Observatory, Cluj-Napoca, Romania
Abstract. The hypothesis of apsidal motion is reviewed and it is found that only such a phenomenon cannot explain the observed O - C diagram, for binary system TX Ursae Majoris.
Key words: eclipsing binary - apsidal motion: TX UMa.
CONVECTION IN THE PRESENCE OF SUNSPOTS
VARUJAN V. PAMBUCCIAN
University of Bucharest, Department of Mathematics
Abstract. The present paper deals with three dimensinal stationary
convection in the presence of a general weak magnetic field and of a strong
magnetic field generated by a sunspot or a group of sunspots. This strong
magnetic field will drive the entire phenomenon.
THE GLOBAL ANALYSIS OF TIME DETERMINATIONS MADE IN BUCHAREST DURING 1962 -1989 (II)
MAGDA STAVINSCHI, DANA DINESCU, GHEORGHE VASS, ALINA DONEA
Astronomical Institute of the Romanian Academy,
Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. The first part of this work was presented during the 7th International Symposium of Geodesy and Geophysics of the Earth - the IAG No. 122 Symposium - in Potsdam and was published in the Proceedings of the Symposium (Springer Verlag, in print). Because at the moment of the Symposium we only had preliminary results of the analysis, in the present paper a complete image of the data processing and of the results has been included.
Key words: Earth's rotation, Time determination.
COLLISION AND NEAR-COLLISION ORBITS IN POST-NEWTONIAN GRAVITATIONAL SYSTEMS
GEORGE BALLINGER*, FLORIN N. DIACU**
Department of Mathematics and Statistics, University of Victoria
P.O. Box 3045, Victoria, B.C., Canada, V8W 3P4
Abstract. We study the central force problem involving a particle of unit mass orbiting a centre while subjected to a post-Newtonian gravitational force proportional to r-² (1 + __ 1n r), where r is the distance to the centre and |__|<1. We examine the behaviour of the paricle at and near collision with the centre. By using McGehee - type transformations we blow up the singularity at r = 0 and obtain regularized equations of motion. After proving the collision manifold to be a torus, a qualitative study of the flow is performed. Collision-ejection solutions are shown to be block-regularizable. Finally, we draw the conclusion that post-Newtonian laws of this type, with - 1 < __<0, are similar to the Newtonian one in the neighbourhood of singularities.
Key words: celestial mechanics - post-Newtonian gravitational
law-collisions.
ON THE CURVATURE OF THE TRAJECTORIES IN THE RESTRICTED PROBLEM OF THREE BODIES
MIRA-CRISTIANA ANISIU
Institute of Mathematics, Cluj-Napoca
Str. Republicii 37, P.O. Box 68, 3400 Cluj-Napoca, Romania
Abstract. It is proved that for the restricted problem of three bodies there are at most three osculating solutions at one point. Points were there are three or two osculating solutions specified.
Key words: Celestial Mechanics - Restricted Three-Body Problem.
TWO - BODY PROBLEM WITH ANISOTROPIC GRAVITATIONAL CONSTANT
VASILE MIOC, CRISTINA BLAGA
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract.The two- body problem corresponding to a gravitational force with anisotropic G is treated by means of perturbation theory. The integration of Newton-Euler equations shows that the perturbed orbit is of elliptic type, lies in a fixed plane, and its semimajor axis, eccentricity, and the argument of pericentre, obtained as functions of the argument of latitude, undergo 2_ periodic variations. The nodal period, determined with an accuracy of first order in a small parameter___ and third order in eccentricity, results to be shorter than the corresponding very general two-body problem with changing equivalent gravitational parameter.
Key words: celestial mechanics - equivalent gravitational parameter - anisotropy of gravitation - orbital motion - perurbation theory.
NODAL PERIOD IN MOTION PERTURBED BY A FORCE ACTING IN ORBIT PLANE
VASILE MIOC
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. An analytic estimate (much improved as against the actual ones) of the nodal period corresponding to an orbit which experiences perturbations due to a force depending in a small parameter and acting in the orbit plane is obtained. The case of radial perturbing force is treated separately. An accuracy of any order in the small parameter and of a desired order in eccentriciry can be reached. The main formulae are applicable to various concrete astronomical situations modelable by this theory.
Key words: celestial mechanics - perturbation theory - orbital motion - nodal period.
ROMANIAN ASTRONOMICAL JOURNAL, VOL. 3, NO. 2, 1993
RELATIVISTIC ROTATING HOMOGENEOUS STARS
VASILE URECHE, ALEXANDRU M. IMBROANE
University of Cluj-Napoca, Astronomical Observatory
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. The components of the metric for a rotational relativistic configuration with axial symmetry developed in spherical harmonics has been put in a non-dimensional form. The differential system has been integrated in the homogeneous case. The stability conditions for some values of parameters p_ and q_ have been obtained.
Key words: relativistic stars - rotation.
ANGULAR MOMENTUM AND ROTATIONAL KINETIC ENERGY FOR RELATIVISTIC POLYTROPES
ALEXANDRU M. IMBROANE
University of Cluj-Napoca, Astronomical Observatory,
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. The angular momentum and the rotational kinetic energy in non-dimensional form have been determined for some values of n and p_ for relativistic polytropic stars, in the spherical symmetry case.
Key words: relativistic stars - rotation
TEMPORAL VARIATIONS OF SOLAR ACTIVITY INDICATORS DURING CYCLE 22*
GEORGETA MARIS, SIMONA DINULESCU, CRISTINA DUMITRACHE
Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract.The present paper investigates the statistical behaviour of sunspots, flares and rapid processes in solar prominences during the ascending phase of the solar cycle 22 (SC 22). The North - South (N - S) asymmetry for phenomena taken into consideration is analysed.
We can remark that the flare number as well as the energetic flares for SC 22, until 1991, have already overtaken the corresponding ones for the whole SC 21.
Key words: solar activity: sunspots, flares, prominences.
CORRELATION BETWEEN THE LONG RADIOWAVE PROPAGATION AND THE GEOMAGNETIC FIELD
GEZA SZOCS
Teacher Training Institute, Eger, Hungary
Abstract. The correlation between the intensity of the radioelectric field of 155 kHz (emitted by Bod - Brasov and received by Cluj-Napoca) and the amplitude of the horizontal component of the geomagnetic field during February - March 1970 is estimated (research performed in the framework of the INTERCOSMOS programme). A delay of three days in the ionospheric response is pointed out. The magnetophere-ionosphere-Earth system is modelled by an RL circuit.
Key words: geomagnetic field - ionospheric absorption - solar-terrestrial relations.
INTERPLANETARY MAGNETIC FIELD INFLUENCE ON THE LOW IONOSPHERE
GEZA SZOCS
Teacher Training Institute, Eger, Hungary
HURA SZOCS
Rando Kalman Engineering Institute, Székesfehérvar, Hungary
Abstract. The correlation between the interplanetary magnetic field induction (measured by Pioneer 3 during July 1980) and the absorption of the radiowaves of 128.048 kHz and 245 kHz in the low ionosphere is estimated. A delay in the ionospheric response of 3 - 4 days and a maximum absorption effect after 7 - 9 days are found.
Key words: solar -terrestrial ralations - ionospheric absorption.
ON THE PHYSICAL AND DYNAMICAL PROPERTIES OF ASTEROIDS
MIREL BIRLAN
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. The paper presents an attempt to study the connection between the physical and dynamical properties of the asteroids. We have studied a sample consisting of 301 asteroids, taking into account eight physical parameters and three dynamical parameters. The method used is the Principal Components Analysis, with which we have searched clusters of asteroids in the histograms obtained in appropriate plans of the parameter space. We have presented also a first comparison with the Tholen taxonomy and with the Hirayama families.
Key words: asteroids, multivariate analysis, principal components method.
EFFECTS OF THE POLE MOVEMENT ON TIME DETERMINATIONS
MAGDA STAINSCHI, DANA DINESCU, GHEORGHE VASS, ALINA DONEA
Astronomical Institute of the Romanian Academy,
Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. Between 1957 and 1990, observations were made in Bucharest with a passage instrument, in order to measure the non-uniformities in the Earth's rotation. We set out to analyse the way in which longitude variations may affect the periodicities indicated by the raw UTO - AT observations (Rom. Astron. J., Vol. 3, No. 1, 1993).
Key words: Earth's rotation, pole meovement, spectral estimators.
CONTRIBUTION TO THE OPTICAL POSITION STUDY OF ____ PERSEI RADIO STAR, CARRIED OU IN THE PERIOD 1969 - 1979
MIHAELA LICULESCU, PETRE POPESCU
Astronomical Institute of the Romanian Academy,
5 Cutitul de Argint St., 75212 Bucuresti, Romania
Abstract.50 optical positions of ___ Persei, observed with the Bucharest Meridian Circle in the Double Stars, NPZT and PZT stars programmes have been compared with similar observations carried out at the Paris and Bordeaux Observatories.
Key words: Meridian observations, ___ Persei.
ON THE EXISTENCE OF CELESTIAL BODIES WITH UN PREDICTABLE MOTION IN THE SOLAR SYSTEM AND ON THE KIRKWOOD GAPS
LENNARD F. BAKKER* and FLORIN N. DIACU**
Department of Mathematics and Statistics,
University of Victoria, Victoria, B.C. Canada
Abstract. The goal of this paper is to bring to the attention of the astronomic community the recent mathematical results of Xia on the existence of the Arnold diffsion in the 3 - body problem and to speculate on its significance for the astronomy of the solar system. We bring evidence that thus result supports the idea of the existence of small celestial bodies with unpredictable behaviour and may expalin completely the formation of the Kirkwood gaps in the belt of asteroids without contradicting previous mathematical studies on this subject.
LIE SERIES AND COMPUTER ALGEBRA TREATMENT OF THE n - BODY PROBLEM
BAZIL PARV
Babes - bolyai University Cluj-Napoca,
Faculty of Mathematics and Computer Science
Str. M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania
Abstract. The solution of the n - body problem (up to the required accuracy order) is given using the Lie series formalism and computer algebra. The symbolic processing generates the FORTRAN source code which calculates numerically the Lie series terms. This generator of FORTRAN programs is general since the number of bodies and the maximum order in expansions are input parameters. It admits further developments according to the concrete problem to be solved.
Key words: Celestial Mechanics - n-Body Problem - Lie Series - Computer Algebra.
ORBITAL MOTION WITH LINEARLY CHANGING EQUIVALENT GRAVITATIONAL PARAMETER
VASILE MIOC
Astronomical Institute of the Romanian Academy,
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. Considering that the equivalent gravitational parameter of a two-body dynamic system is linearly time-dependent, µ = A + Bt, the behaviour of an elliptic-type orbit is studied. The perturbations of all orbital elements are determined to first order in B, using Delaunay-type canonical variables and a method due primarily to von Zeipel. Solving the equations of motion, besides periodic perturbations, one points out secular and mixed perturbations in semimajor axis and eccentricity (hence unstable orbit), as well as in the mean anomaly, and mixed perturbations in the argument of pericentre (hence apsidal motion). As expected, the semilatus rectum and the position of orbit palne remain unchanged. The model can be applied to various concrete astronomical situations.
Key words: celestial mechanics - perturbed orbital motion - equivalent gravitational parameter - von Zeipel's method.
EFFECTS OF ATMOSPHERIC DENSITY SEMIDIURNAL VARIATION ON ARTIFICIAL SATELLITE DYNAMICS
VASILE MIOC, EUGENIA RADU
Astronomical Institute of the Romanian Academy,
Astronomical Observatory Cluj - napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
Abstract. The separate influence of the semidiurnal variation of the atmospheric density (whose distribution is described by the TD thermospheric model) on artificial satellite motion is studied. First order effects are pointed out through both perturbations of orbital elements over one nodal period, and the difference between the nodal and Keplerian periods. The respective analytic formulae are deduced for satellites moving in low eccentric orbits. Some particular cases are discussed.
Key words: artificial satellites - atmospheric drag perturbations - TD thermospheric model.
ON THE DETERMINATION OF THE AERODYNAMIC DRAG PARAMETER OF INTERCOSMOS 19 ROCKET ( 1979 - 20B)
MAGDALENA CARSMARU, TIBERIU OPROIU
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. In the present paper we have presented the determination of the aerodynamic drag parameter of Intercosmos 19 Rocket. We have used the Goral's method, which we have applied also in the case of DTM and of C atmospheric models. The results are in agreement with the values obtained by means of the "classical" method.
Key words: Artificial satellites, Upper Atmosphere, Aerodynamic
Drag Parameter.