ON AVERAGING-BASED METHODS FOR CONSTRUCTING SOLUTIONS IN CELESTIAL MECHANICS PROBLEMS
EUGENIU GREBENICOV
Institute for Problems of Cybernetics of the Russian Academy of Sciences37 Vavilova St., Moscow 117312, Russia
Abstract. The paper presents someanalytic methods based on the averaging principle, intended to construct solutions for small parameter problems belonging to celestial mechanics. A phase space with action-angle phase variables is used. The first order averaged equations for the planetary three-body problem are constructed. The construction of averaged equations of any order is presented. The necessary and sufficient conditions to make trigonometric the corresponding perturbative theory are specified. The determination of the initial data used in the integration of the averaged equations of any order is presented in detail.
Key words: celestial mechanics - averaging-type methods - perturbation theory
A NEW CLASS OF ANALYTIC STELLAR MODELS
VASILE URECHE
University of Cluj-NapocaFaculty of Mathematics and Computer ScienceStr. M. Kogalniceanu 1, 3400 Cluj-Napoca, RomaniaAbstract. A new class of analytic stellar models is proposed, supposing that the product between the local values of gravitational acceleration and density is constant. The distributions of the density, pressure, temperature, and mass are determined, and the values of global parameters are obtained. It is proved that the considered models are quasi-homogeneous. The models satisfy Chandrasekhar's conditions of stability.
Key words: astrophysics - stars - analytic models
PHOTOMETRY OF THE SPOT STAR BY DRA DURING 1993A.
DUMITRESCU, G. OPRESCU, F. DONEA
Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. Photometry in bands BV was obtained for the spot star BY DRA during 1993 at the Bucharest Observatory. The Amplitudes of the light curves in V and B are 0.08 and 0.07, respectively. A small B - V colour variation is observed. The minimum of the light curve is shifted at phase 0.5.
Key words: BY variables - wide-band photometry
A MODEL OF A STATIC STAR ON A 2 + 1 DIMENSIONAL BACKGROUNDSILVIA
ONOFREI, MARIUS I. PISO
Gravitational Researches Laboratory,
21, Ana Ipatescu Blvd., 71111 Bucharest, Romania
Abstract. The aim of this issue is to give some general information about the (2 + 1)-dimensional general relativity. As a direct application of these considerations a model of a static star, formed of a perfect fluid, in (2 + 1)-dimensions is presented.
Key words: general relativity - static stars
SOURCE FLARES OF TYPE II SOLAR RADIO BURSTS DURING SOLAR CYCLE 21
GEORGETA MARIS, EMILIA TIFREA
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212 Bucharest 28,
Romania
Abstract. A preliminary analysis of type II and complex type II + IV Solar Radio Bursts (SRBs) during solar cycle (SC) 21 was done in a previous paper (Maris and Tifrea, 1994). The yearly distributions of these SRBs as well as the yearly and heliographic distributions of their source flares are, in this paper, discussed. the yearly distributions of analyzed phenomena present more than one maximum during SC 21. The heliographic distributions of the source flares, in latitude and longitude, were also not uniform, but they are in good agreement with the distributions of other solar activity phenomena.
Key words: Solar activity - solar flares, type II and type IV solar radio bursts
GEOEFFECTIVENESS OF CORONAL MASS EJECTIONS ASSOCIATED WITH SOLAR
FILAMENT DISAPPEARANCES
SIMONA DINULESCU and GEORGETA MARIS
Astronomical Institute of the Romanian AcademyStr. Cutitul de Argint 5, 75212 Bucharest 28, Romania
Abstract. The relations of the Coronal Mass Ejections (CMEs) with the solar filament disapperances (FDs), in general not associated with active regions or with flares within active regions, are analysed. For the beginning, we choose the years 1979 - 1980, the maximum phase of solar cycle 21. For each associated phenomenon, CME + FD, the possible geophysical effects, namely: sudden storm commencement (SSC), geomagnetic storm (GS), solar proton event (SPE) and variation of the Ap index, were looked for. A remarkable high percent of association between CME + FD events and geophysical effects was registered in the two years.
Key words: coronal mass ejections - filament disappearances - geophysical effects
ANALYSIS OF THE LONG PERIOD TERMS OF LOCAL AND GLOBAL DATA OF UT1 - AT
MAGDA STAVINSCHI (1), JEAN SOUCHAY (2), ALINA-CATALINA DONEA (1)
(1) Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint 5, Ro - 75212, Bucharest, Romania
(2) Observatoire de Paris
61, Avenue de l'Observatoire, F-75014 Paris, France
Abstract.In our analysis of UTO and UTI, the long period terms 18.6y, 13.9y, 12.5y, 11.1y, 9.2y have been emphasized. To be sure that the results are trustworthy, different methods (Scargle for data unevenly distributed,the classical least square method and Fourier analysis) have been used for the data recorded as well at the Bucharest Observatory and the data of IERS.
Key words: spectral estimators - the least squares method - Fourier analysis - Earth rotation
AN ANALYTIC ASYMPTOTICAL SOLUTION IN THE THREE-BODY PROBLEM
DAN SELARU, CATALIN CUCU-DUMITRESCU
Institute for Gravitation and Space SciencesBd. Ana Ipatescu No. 21, 71111 Bucharest, RomaniaAbstract. This study presents a method of obtaining asymptotic approximations for motions near a Lagrangepoint in the restricted, plane, elliptical three-body problem. The calculations are carried out for a first order, escape solution from the proximity of the equilateral Lagrange point L4, where the primaries motion's eccentricity is taken as the small parameter.
Key words: celestial mechanics - three-body problem
STOCHASTIC SET-UP OF THE TWO-BODY PROBLEM
CRISTINA STOICA
Institute for Gravitation and Space Sciences
21, Ana Ipatescu Bvd., 71111 Bucharest, Romania
GH. STOICA
University of Bucharest, Mathematics Department,14, Academiei St., 70109 Bucharest , RomaniaAbstract. Using Bismut's approach to the stochastic canonical system, this paper applies stochastic methods to the concrete case of the perturbed two-body problem.
Key words: celestial mechanics - two-body problem
SOLAR SYSTEM TEST FOR THE EXISTENCE OF GRAVITATIONAL WAVES
NICHOLAS IONESCU-PALLAS, MARIUS I. PISO, SILVIA SAINAR
Gravitational Researches Laboratory
21 Ana Ipatescu blvd., 71111 Bucharest, Romania
Abstract. Starting from a static spherically symmetric solution of the Einstein's field equations in the second approximation in the perfect fluid scheme, in the exterior of the source, the corresponding metrics depend on a dimensionless parameter a Taking the Sun for the source, the influence of a on the classical Solar System tests of the general relativity is estimated, the only a -dependent one being the Sharipo radar-echo delay experiment. Performing such a test in given conditions within a precision better then 10-², it is possible to obtain an experimental value for a If a = 1, the Einstein's equations in the weak field approximation take the D'Alembert form, which attests the existence of gravitational waves.
Key words:general relativity - solar system tests - exact solutions
A SOLUTION TO BRING THE NATIONAL ASTRONOMICAL-GEODETIC NETWORK FROM S/42 SYSTEM TO WGS-84 SYSTEM
ION RADU
Military Astronomical Observatory, Bucharest, RomaniaAbstract. In the framework of a Romanian-Bulgarian cooperation, the Military Astronomical Observatory Bucharest integrated GPS measurements with points in the Southern zone of the national geodetic network. Molodensky's, Zhogolovich's and Ihde's relations were used to pass from S/42 system to WGS-84 system. Six variants for the choice of common points were considered.
Key words: satellite geodesy - GPS measurements
DETERMINATIONS OF BUCHAREST-SOFIA SPACE VECTOR IN S/42 AND WGS-84 SYSTEMS
ION RADU, CONSTANTIN TIGANILA
Military Astronomical Observatory, Bucharest, RomaniaMINCHO MINCHEV
Military Topographic Service, Sofia, BulgariaAbstract. A main result of ROMBUL'92 GPS campaign in connecting the astronomical-geodetic networks of Romnia and Bulgaria is presented. The Bucharest-Sofia vector is determined using separately three intermediate points. Both ellipsoidal and rectangular coordinates were used. The computations were performed in both S/42 and WGS-84 reference systems.
Key words: satellite geodesy - GPS measurements
ROMANIAN ASTRONOMICAL JOURNAL, VOL.4, NO.2,1994
ON THE MATHEMATICAL SUBSTANTITION OF INTERPOLATION AVERAGING SCHEMES FOR SOME PROBLEMS OF CELESTIAL MECHANICS
EUGENIU GREBENICOV (1), ARPAD PAL (2)
(1) Institute for Problems of Cybernetics of the Russian Academy of Sciences
37, Vavilova St., Moscow 117312, Russia
(2) Babes-Bolyai University, Faculty of Mathematics and Computer Science1, M. Kogalniceanu St., 3400 Cluj-Napoca, RomaniaAbstract. The interpolation averaging schemes proposed by N.D. Mojseev are being mathematically substantiated. Some problems which arise from the application of these schemes are emphasized and analysed. Mojseev's method is found to be substantiated in Bogolyubov's meaning.
Key words: celestial mechanics - Hamiltonian systems - averaging method
WEIGHTED BI-POLYTROPIC MODELS FOR WHITE DWARFS. ANALYTIC APPROACH
VASILE URECHE (1), VASILE MIOC (2)
(1) University of Cluj-Napoca, Faculty of Mathematics and Computer Science
1, M. Kogalniceanu St., 3400 Cluj-Napoca, Romania
(2) Astronomical Institute of the Romanian Academy, Astronomical ObservatoryCluj-Napoca 19, Ciresilor St., 3400 Cluj-Napoca, RomaniaAbstract. A two-parametric class of weighted bi-polytropic models for white dwarfs (consisting of a weighted combination of the polytropes of indices 3/2 and 3) is being proposed. The configuration is found to be dynamically stable for all weighting coefficient values within the interval [0, 1]. An equation analogous to Lane-Emden polytropic equation is established. Some properties of the power series approximating the solution in the neighbourhood of the centre are pointed out. A mass-radius relation is established, and an expression for Chandrasekhar's limiting mass is obtained. A numerical analysis of the considered class of models will be performed in a subsequent paper.
Key words: astrophysics - barotropic stellar models - white dwarfs
OBSERVATIONS AND LIGHT CURVE OF NSV8587
JOSE F. LAHULLA, JOSE PENSADO
Observatorio Astronomico Nacional
Alfonso XII, 3, 28014 Madrid, Spain
Abstract. Blue and yellow photoelectric observations of the eclipsing binary system NSV8587 were made on 20 nights during 1984 to 1991. A listing of all the observations and the corresponding light curve and ephemeris are given. The photometric colors, the asymmetry in the light curve and the period suggest that the star is a dwarf Cepheid.
Key words: eclipsing binaries
NEW LIGHT ELEMENTS OF THE RS CVn-TYPE BINARY RT ANDROMEDAE
H. ROVITHIS-LIVANIOU¹ , P. ROVITHIS², A. KALIMERIS¹'²
G. OPRESCU³, A. DUMITRESCU³, D.M. SURAN³
1 Section of Astrophysics, Astronomy and Mechanics, Dept. of Physics
Athens University Panepistimiopolis, GR 157 84, Athens, Greece
2 Astronomical Institute, National Observatory of Athens
P.O. Box 20048, Athens 118 10 , Greece
3 Astronomical Institute of the Romanian Academy
5, Cutitul de Argint St., 75212 Bucharest 28, RomaniaAbstract. In the present study the (O-C) diagram of the eclipsing binary RT Andromedae was constructed, using all minima times found in the literature. It can be described very well by a third or a fourth order polynomial, but a quadratic least square fitting is also expressing it well enough. The latter shows that the period RT And continues decreasing with a mean rate of 3.1E-10, if the quadratic least square fitting is applied to all minima, regardless of their kind. Moreover, linear least square fitting to the recent photoelectric minima yields to a new ephemeris formula which is proposed for the future observations of the system.
Key words: variable stars - eclipsing binary stars - RS CVn
binaries
RELATIONSHIP BETWEEN FLARES AND MAGNETIC FIELD TOPOLOGY
SIMONA DINULESCU, ALEXANDRA DIMITRIU, GEORGETA MARIS
Astronomical Institute of the Romnian Academy5, Cutitul de Argint St., 75212 Bucharest 28, RomaniaAbstract. The present paper takes into consideration three sunspot groups which constituted the objective of some special campaigns of solar observations. We have proposed the analysis of the general behaviour of three sunspot groups which belong to active centers that appeared under different conditions of the large-scale solar magnetic field and the distribution of flares which appear in each group taking into consideration all the observed flares. The deduction of the general characteristics of all groups and of those specific to each group as far as eruptions are concerned.
Key words: solar activity - solar magnetic field – sunspots - flares
OBSERVATIONS OF COMET SWIFT-TUTTLE IN 1992
GHEORGHE BOCSA
Astronomical Institute of the Romanian Academy5, Cutitul de Argint St., 75212 Bucharest 28, RomaniaAbstract. The precise positions of comet Swuft Tuttle observed at Bucharest Observatoey in 1992 are presented. For performing the observations, a 380/6000 mm astrograph was used, the plates measurements were carried out at ASCORECORD machine and the computations were done on a PC Computer.
Key words: photographical astrometry - Swift-Tuttle comet
PHOTOGRAPHIC OBSERVATIONS OF JUPITER AND OF ITS GALILEAN SATELLITES
GHEORGHE BOCSA
Astronomical Institute of the Romnian Academy5, Cutitul de Argint St., 75212 Bucharest 28, RomaniaAbstract. This paper presents the positions of Jupiter and of its Galilean satellites observed at Bucharest Observatory in 1982, 1984 and 1985. The observations were performed with a 380/6000 mm astrograph, the plates measurements were made with an ASCORECORD machine and the computations were made on a PC computer.
Key words: photographical astrometry - Jupiter and Galilean
satellites
WIDE-FIELD PLATE ARCHIVE DATABASE IN BUCHAREST
G. VASS, G. BOCSA, V. IONESCU, A. ALEXIU, M. BIRLAN
Astronomical Institute of the Romanian Aacademy5, Cutitul de Argint St., 75212 Bucharest 28, Romania
Abstract. The paper presents the wide-field plates identification archive database made in Bucharest for the photographic observations performed here in more than 60 years: 1930-1993. This database was realised in coooperation with the IAU Working Group for Wide-Field Imaging and it is included in the Wide-Field Imaging Plate Database.
Key words: Wide-field imaging - astronomical databases - photographic astrometry - data archives
A PRELIMINARY ANALYSIS OF THE DATABASE FOR WIDE-FIELD PLATE ARCHIVE IN BUCHAREST
Astronomical Institute of the Romanian Academy5, Cutitul de Argint St., 75212 Bucharest 28, RomaniaAbstract. A preliminary analysis of identification database for wide-field plate archive in Bucharest, concerning the distribution of plates in time, observed objects and other characteristics, is presented.
Key words: wide-field imaging - astronomical database - photographic astrometry - data archives
RAPID AERODYNAMIC EFFECTS IN ARTIFICIAL SATELLITE NODAL PERIOD
VASILE MIOC, EUGENIA RADU, LIVIU MIRCEA, ADRIAN CRISTEA
Astronomical Institute of the Romanian AcademyAstronomical Observatory Cluj-Napoca19, Ciresilor St., 3400 Cluj-Napoca, RomaniaAbstract. The combined influence of the rapid effects (North-South asymmetry, diurnal and semidiurnal variations) in atmospheric density distribution (described by the TD atmospheric model) on artificial satellite nodal period is being studied. First order effects are pointed out for satellites moving in low eccentric orbits. The resulting formulae allow for considering separately each of the three effects taken into account. Some particular cases are suggested.
Key words: artificial satellites - atmospheric drag perturbations - TD thermospheric model
ON THE DETERMINATION OF THE TOTAL MECHANICAL ENERGY OF AN ARTIFICIAL SATELLITE
MAGDALENA CARSMARU, TIBERIU OPROIU
Astronomical Institute of the Romanian AcademyAbstract. The paper deals with the determination of the total mechanical energy per unit mass of an artificial satellite. An approximate formula for the computation of the total mechanical energy decrease due to atmospheric drag is proposed. Such a determination is necessary for the evaluation of the amount of fuel for maintaining a space vehicle in a given low orbit. An application to Intercosmos 19 Rocket is made.
Key words: artificial satellite - atmospheric drag - mechanical
energy
ON THE "ELLIPTIC" MOTION IN THE SCHWARZSCHILD GRAVITATIONAL FIELD
DAN SELARU
Institute for Gravitation and Space Sciences21, Ana Ipatescu BD., 71111 Bucharest, RomaniaAbstract. The elliptic-type motion in a Schwarzschild gravitational field is being studied by an averaging method. We studied the first and the second order perturbations of orbital elements. The time of prediction is of order 1/e (where e is the small parameter).
Key words: Schwarzschild gravitational field.
HAMILTONIAN TREATMENT OF SOME SPACE-TIME MODELS OF COSMOLOGICAL AND ASTROPHYSICAL INTEREST
DUMITRU N. VULCANOV
University of Timisoara, Theoretical and Computational Physics Dept.,
4, V. Parvan Bd., RO - 1900 Timisoara, Romania
Abstract. The article presents new results in the Hamiltonian treatment of some space-time models: Bianchi I/Kantowski-Sachs, axisymmetric Cooperstock model and the superdense star model. The dynamic variables in a specific form for each model are introduced, together with the components of the canonical conjugate momentum. Thus, the dynamic and the constraint equations are obtained. The models are processed with special procedures (elsewhere presented) of algebric programming on PC Machines, with EXCALC package.
Key words: cosmological models - Hamiltonian treatment
ON CHARACTERISTIC TIME IN THE ANALYSIS OF VARIABLE STAR PERIODICITY
ALEXANDRU POP
Astronomical Institute of the Romanian Academy,Astronomical Observatory Cluj-Napoca,
19, Ciresilor St., RO-3400 Cluj-Napoca, Romania
Abstract. A definition of the characteristic time associated to a given equally spaced observational data set on a variable star with changing period is proposed. The conditions to be fulfilled by definition are discussed. Two examples (perturbations illustrated by polynomial law and arbitrary periodic law) are given.
Key words: variable stars - stellar photometry - periodicity analysis