COLLISION AND ESCAPE DYNAMICS IN FOCK'S FIELD

ROMANIAN ASTRONOMICAL JOURNAL

Vol. 10, No. 2, p. 113-208, Bucharest, 2000

FIRSTGROUND-BASED BVPHOTOMETRY

OF THEECLIPSING BINARYVW LEOMINORIS

ALEXANDRU DUMITRESCU

Astronomical Institute of the Romanian Academy

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

E-mail: alex@roastro.astro.ro

Abstract. The paper presents the first ground-based photoelectric observations of the newly discovered eclipsing binary VW Leo Minoris. The observations were carried out with an EMI 9502 B type photomultiplier attached to the 50 cm Cassegrain reflector of the Bucharest Observatory.The light curves in B and V colors are presented.

Key words: photoelectric photometry – eclipsing variable stars.

HIGH-SPEEDPLASMA STREAMSIN SOLARWIND

DURING THEELEVEN YEARSSOLAR CYCLE(I)

GEORGETA MARIS ¹, OVIDIU MARIS ²

¹ Astronomical Institute of the Romanian Academy

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

E-mail: gmaris@roastro.astro.ro

² Space Science Institute

Str. AtomiStilor 1, P.O. Box MG-6, RO-76900 Bucharest - Magurele, Romania

E-mail: maris@venus.nipne.ro

Abstract. The characteristics of the high-speed plasma streams (HSPS) in the solar wind during the eleven years solar cycle are investigated taking into account only their importance. The analysis is performed on solar cycles 20–22 (more precisely, 1964–1982), separately on the different types of HSPS according to their solar origin. The HSPS solar sources cannot be only solar flares and coronal holes but every energetic event able to produce particle acceleration. The differences between the solar cycle 20 and 21, found in the present study, could be due to the structure of the 22-years solar magnetic cycle.
Key words: solar wind – high-speed plasma streams – 11-years solar cycle.

PHYSICS OF THE BASE OF THE OUTFLOW JET

IN ACTIVE GALACTIC NUCLEI

FANEL DONEA, ALINA-CATALINA DONEA

Astronomical Institute of the Romanian Academy,

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

E-mail: fdonea@roastro.astro.ro

Abstract. A new aspect of the physics of the base of the outflow jet at the center of an active galactic nuclei is addressed. The energy budget, including the conservation laws of mass are analysed in the context of the existence of a self-symbiotic system with a black hole, a relativistic disc and a bipolar outflow. The velocity of expansion of the jet anchored at the boundary layer is analysed. A thorough discussion is dedicated to the boundary layer and the corona of the accretion disc. Key words: accretion disc – X-ray fluxes – active galactic nuclei – symbiosis.

EMISSIONIN ABSORBTIONLINES: RESULTS

OF THESL9 LNUCLEUS IMPACTWITH JUPITER

MIREL BÎRLAN1,2

¹ Observatoire de Paris-Meudon, DESPA

F-92195 Meudon Cedex, France

E-mail: Mirel.Birlan@obspm.fr

² Astronomical Institute of the Romanian Academy

Str. Cutitul de Argint, RO-75212 Bucharest 28, Romania

Abstract. High-resolution spectra of the impact sites and impact of the comet Shoemaker-Levy 9 with Jupiter have been performed at the Pic-du-Midi Observatory. The excitation of several chemical elements (Fe, Ca, Ba, Na, Mn, Mg, etc.) has been identified during the analysis of the L nucleus impact spectra obtained in visible and near-IR. The article presents the atomic lines and the time evolution of nine of them. Key words: spectroscopy – comets – atomic lines.

ANECESSARY CONDITIONFOR COLLISION

IN THETWO-BODY PROBLEM

WITH QUASIHOMOGENEOUSPOTENTIALS

VASILE MIOC, MAGDA STAVINSCHI

Astronomical Institute of the Romanian Academy

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

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

Abstract. Mioc and Stavinschi (2000) proved that in the two-body problem associated to quasihomogeneous potentials (sums of homogeneous potentials) all singularities are due to collisions. In this note we prove a necessary condition for collisions to occur: the coefficient corresponding to the maximum degree of homogeneity must be nonnegative. Key words: celestial mechanics – two-body problem – quasihomogeneous potentials –collisions.

ESCAPEDYNAMICS INQUASIHOMOGENEOUS FIELDS

VASILE MIOC, MAGDA STAVINSCHI

Astronomical Institute of the Romanian Academy

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

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

Abstract. The escape in the two-body problem associated to a quasihomogeneous potential (a sum of homogeneous potentials) is being tackled. The basic equations of the problem are put in a form for which the infinity is a singularity, then they are regularized via McGehee-type transformations. The singularity is replaced by a manifold pasted on the phase space, and the flow on this manifold is described; it is identical with the analogous flows corresponding to already studied concrete astronomical and physical situations. Key words: celestial mechanics – quasihomogeneous fields – escape.

THE THREE-AXIAL EARTH ROTATION:

A NEW MATHEMATICAL APPROACH

VASILE MIOC, MAGDA STAVINSCHI

Astronomical Institute of the Romanian Academy

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

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

Abstract. The three-axial Earth's rotation is generally treated by quantitative methods. The seldom used qualitative analysis, which depicts the general evolution all along the motion, can offer supplementary information. Tackling the problem from such a viewpoint, we exploit its Hamiltonian description using Andoyer-type variables, and consider it via KAM (Kolmogorov-Arnold-Moser) theory. The system of motion equations fulfils the condition of so-called "isoenergetic nondegeneracy". In astronomical translation, this means that the Earth's rotation is "sure" for almost all initial conditions: the chances for a drastic change are extremely improbable; this corroborates the data provided by observations and quantitative analysis. Another result offered by KAM theory is that the polhody will always be confined to a relatively negligible area. As a finel conclusion, the most various methods of mathematics, classical mechanics, celestial mechanics must be used to understand astronomical problems of essential importance, as the Earth's rotation is. Key words: celestial mechanics – Earth's rotation – KAM theory.

EXISTENCEOF QUASIPERIODICORBITS

IN MANEV-TYPEPROBLEMS: ANEW PROOF

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@roastro.astro.ro

Abstract. A new proof of the existence of quasiperiodic motion in the Manev-type two-body problem is provided via classical mechanics methods. The set of such orbits is dense in the set of bounded noncollisional trajectories. This allows one to apply the classical results of KAM theory to this problem. Key words: celestial mechanics – Manev-type fields – quasiperiodic orbits.

THEBUCHAREST OBSERVATORYPHOTOGRAPHIC OBSERVATIONS INTHE WIDE-FIELDPLATE DATABASE

MILCHO TSVETKOV ¹,MAGDA STAVINSCHI ²,KATYA TSVETKOVA ¹,

KONSTANTIN STAVREV ¹,GHEORGHE BOCSA ²,VASIL POPOV ¹

CORNELIA CRISTESCU ²

¹ Institute of Astronomy, Bulgarian Academy of Sciences

72 Tsarigradsko Shosse Blvd., BG-1784 Sofia, Bulgaria

E-mail: tsvetkov@skyarchive.org

² Astronomical Institute of the Romanian Academy

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

E-mail: magda@roastro.astro.ro

Abstract. The data in the Wide-Field Plate Database for the archived photographic observations obtained with the 0.38 m refractor and the 0.16 m camera of the Bucharest Observatory in the context of the their repeated use are being analyzed. A summary of the observational programs carried out with these two instruments since 1930 is presented. Results from the scanning of selected plates with the PDS 1010 of the Sofia Sky Archive Data Center are presented, too. Key words: photographic observations – archiving – large databases.

THEARCHIVE OF ASTROMETRIC PLATES OBTAINED

AT THE ASTRONOMICAL OBSERVATORY OF CLUJ

GHEORGHE DORIN CHIS, CRISTINA BLAGA, LIVIU MIRCEA

Astronomical Institute of the Romanian Academy

Astronomical Observatory Cluj-Napoca

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

E-mail: dorin@roastro.astro.ro, cpblaga@math.ubbcluj.ro, liviu@email.ro

Abstract. Within the framework of the Wide-Field Plate Database Project we have begun to archive the photographic plates kept in the library of the Cluj Observatory. The aim of this note is to present the wide-field plates obtained at Cluj between 1952 and 1957. These plates contain 142 positions of 15 small planets and 4 comets. Key words: astrometry – wide field plates archive.

Lightcurve andtimes ofminima forHU Tau fromvisual observations

VALERIU TUDOSE, ADRIAN SONKA

Faculty of Physics, University of Bucharest

Str. AtomiStilor 1, P.O. Box MG-6, RO-76900 Bucharest -Magurele, Romania

E-mail: tudosev@yahoo.com, senko@personal.ro

Abstract. In this paper we determine three times of minima and we represent the light curve of HU Tau. The visual observations were performed during December 1998, in Bucharest, with a 50 mm refractor, F/D=8. Key words: visual photometry – eclipsing binaries – HU Tau.