STRUCTURAL PARAMETERS OF DY PEGASI
LIGHT CURVES BETWEEN 1949 1987

ALEXANDRU POP, ADRIAN CRISTEA, VLAD TURCU

Astronomical Institute of the Romanian Academy

Astronomical Observatory Cluj-Napoca

Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania

E-mail: apop@academie.cj.edu.ro, acristea@usa.net

Abstract. Structural changes of DY Pegasi light curve shape are being studied using both traditional and Fourier-type structural parameters. In order to perform this investigation we applied the Fourier decomposition technique to each considered data set.The values of the above mentioned structural parameters were then calculated.



 

THE 22-YEAR SOLAR MAGNETIC CYCLE.

I. SUNSPOT AND RADIO ACTIVITY

GEORGETA Maris, ADRIAN Oncica, MIRUNA DANIELA Popescu

Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania

E-mail: gmaris@aira.astro.ro, adrian@aira.astro.ro, miruna@aira.astro.ro

Abstract. The magnetic polarities of the solar active regions in each hemisphere reverse from one 11-year activity cycle to the next. The same is true for the polarity of the poles. Thus, the magnetic solar activity exhibits a 22-year recurrence known as the Hale Cycle. Previous studies have suggested that the correct choice for cycle pairing is "even-odd" (in that order) the second one being more powerful. Based on a bimodal behaviour of even-odd solar cycle pairs, it was predicted a higher amplitude for the solar cycle 23. Nevertheless this cycle reached its maximum smoothed number RM of only 120.8, much lower than the predicted value. We analyse sunspot relative numbers and 10.7 cm radio flux data during the ascending phases of the 11-year solar cycles 22 and 23. In order to point out possible intrinsic different behaviour between the odd even components of the magnetic cycle, we limit ourselves to the ascending phases only. These periods are less influenced by the overlapping effect seen usually on the descending phase. We investigate spectral features in our time series data together with their time evolution using some of the tools provided by Joint Time-Frequency Analysis. We found substantial lack of correlation between the two ascending phases. Our JTF Analysis showed also different trends in time behaviour and variability content.

FAMILIES OF STRAIGHT LINES

IN PLANAR POTENTIALS

GEORGE BOZIS 1, MIRA-CRISTIANA ANISIU 2

1 Department of Physics, University of Thessaloniki

GR-54006 Thessaloniki, Greece

E-mail: gbozis@ccf.auth.gr

2 "Tiberiu Popoviciu" Institute of Numerical Analysis

P. O. Box 68, RO-3400 Cluj-Napoca, Romania

E-mail: mira@math.ubbcluj.ro

Abstract. It is shown that all planar potentials V(x, y) that can give rise, among other conditions, to monoparametric families of straight lines (FSL) satisfy a condition, expressed in the form of a second order nonlinear partial differential equation in V. To each such potential there corresponds just one FSL, whereas each preassigned monoparametric FSL can be created by infinitely many potentials. Various types of potentials (e.g., separable, homogeneous, etc.) producing FSL are studied. A necessary and sufficient condition is found, satisfied by all "adelphic" families of orbits, i.e. families that can coexist with a given FSL.
 
 
THE EQUILIBRIUM POINTS

IN THE PHOTOGRAVITATIONAL MODEL

OF CONSTANTIN POPOVICI

VASILE MIOC

Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania

E-mail: vmioc@aira.astro.ro

CRISTINA BLAGA

Astronomical Institute of the Romanian Academy

Astronomical Observatory Cluj-Napoca

Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania

E-mail: cpblaga@math.ubbcluj.ro

Abstract. We discuss the two-body problem within the framework of the photogravitational model proposed by the Romanian astronomer Constantin Popovici. The motion equations in polar coordinates and the angular momentum integral are established, then transposed in McGehee-type variables. The qualitative analysis of the differential system allows an easy identification of the equilibrium points, as well as the study of their nature. The results are compared with those obtained by other authors.



 
 

A NEW ANALYTIC SOLUTION FOR THE MANEV-TYPE TWO-BODY PROBLEM

CRISTINA STOICA 1, VASILE MIOC 2

1 University of Victoria, Department of Mathematics and Statistics

Victoria, B. C., V8W 3P4, Canada

E-mail: cstoica@math.uvic.ca

2 Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania

E-mail: vmioc@aira.astro.ro

Abstract. The analytic solutions of the Manev-type two-body problem, obtained both perturbatively and by direct integration are being revisited. A new solution is provided starting from the first integral of energy. The equivalence of the new solution with the old ones is proved.


A NEW SET OF LISSAJOUS-TYPE COORDINATES

FOR HAMILTONIAN SYSTEMS

C?T?LIN CUCU-DUMITRESCU

Computer M&S 95

Bd. Aviatorilor 23, Bucharest, Romania

E-mail: ufh@pcnet.ro

Abstract. The motion described by two-degrees-of-freedom canonical systems is being considered. One passes from Cartesian to polar coordinates, then makes the system autonomous. The second step introduces Levi-Civita parabolic polar coordinates and rescales the time. At the last step, a new set of Lissajous-type coordinates is introduced. These ones give a remarkable form to the Hamiltonian, making its main part directly integrable. Some concrete astronomical situations to which the model is applicable are presented.
 
 
 
 
INFLUENCE OF THE EVEN ZONAL HARMONICS

OF THE GEOPOTENTIAL ON GPS SATELLITE ORBITS

STELIAN COJOCARU

Romanian Naval Academy, Navigation Department

Str. Fulgerului 1-3, RO-8700 Constanta, Romania

E-mail: cojocarus@yahoo.com

Abstract. The Global Positioning System represents the most widespread, latest fashioned tool for astronomers, geodesists, hydrographers and navigators in their attempt to determine the positions of points of interest on the Earth, sea and space. The paper investigates the most important part of the perturbing acceleration that influences the GPS satellite osculating elements: the non-central part of the gravitational field of the Earth. First, an analytical investigation of the effect of zonal harmonics of the geopotential is performed. Second, a numerical, discriminatory evaluation is achieved and finally a few important conclusions are being drawn.
 

OBSERVATIONS OF PLUTO IN BUCHAREST

DURING 1932 AND 1967-1975:

PRECISE POSITIONS AND MAGNITUDES

GHEORGHE BOCSA

Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania

E-mail: gbocsa@aira.astro.ro

Abstract. The observations of Pluto obtained in 1932 and during 1967-1975, performed at the Astronomical Observatory of Bucharest with the 380/6000 mm astrograph are presented. Both Turner's (constants) and Schlesinger's (dependencies) methods were used for the computation of the normal coordinates of the object.
 
 

HARETU AND THE STABILITY OF THE SOLAR SYSTEM

FLORIN DIACU 1, TUDOR RATIU 2

1 Pacific Institute for the Mathematical Sciences

and

Department of Mathematics and Statistics

University of Victoria, P. O. Box 3045

Victoria, B. C., V8W 3P4, Canada

E-mail: diacu@math.uvic.ca

2 Département de mathématiques

École Polytechnique Fédérale de Lausanne

CH-1015 Lausanne, Switzerland

E-mail: Tudor.Ratiu@epfl.ch

Abstract. We discuss the contributions of Spiru Haretu to the problem of the solar system's stability and show their importance relative to the mathematics research of the late 19th century. We also give a brief survey of the subsequent developments and the consequences of Haretu's results.

SPIRU HARET'S CONTRIBUTION

TO CELESTIAL MECHANICS

VASILE MIOC, MAGDA STAVINSCHI

Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania

E-mail: vmioc@aira.astro.ro, magda@aira.astro.ro

Abstract. The contribution of Spiru Haret to astronomy, especially to the problem of solar system stability, is being emphasized. The pre- and post-Haret results in this domain are also pointed out.