The Maximum Of The Total Solar Eclipse Was In Romania

Magda Stavinschi
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: magda@roastro.astro.ro

Abstract. The maximum of the last total solar eclipse of the second millenium was in Romania. In spite of the bad weather, some experiments were successful. A short presentation of what happened in Romania could contribute to a clearer image of what this event was.

Key words: total solar eclipse - instruments.
 
 
 

Influence Of The Outflow Jet On The Accretion Disk Structure In AGN

Alina-Catalina Donea
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: adonea@roastro.astro.ro

Abstract. It is widely accepted that the center of an active galactic nucleus has a supermassive black hole surrounded by an accretion disk. The radio emissions reveal the existence of the outflows, which are believed to originate from the innermost region of the disk. The most recent optical and radio observations of AGN and the discovery of the quasi-periodic oscillations in X-ray binaries reveal the importance of searching the inner edge of the accretion disk assumed to be essential for the formation of the jet in any kind of AGN. Based on the assumption that the jet, the disk and the black hole are symbiotic elements of a stable active system, we analyze the characteristic radii of the disk with jet. The loss of mass and angular momentum through the jet channel implies a recalculation of the structure of the disk, where opacity and pressure change.

Key words: small accretion flow - active galactic nuclei - outflow
 
 
 

General Relativistic Effects On Accretion Disc Spectra

Fanel Donea
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212 Bucharest, Romania
E-mail: fdonea@roastro.astro.ro

Abstract. The system under consideration is a Kerr black hole, surrounded by a relativistic accretion disc. The Novikov -Thorne model is used for the accretion disc. General relativistic effects influnce the trajectories of the photons that leave the accretion disc, hence influencing the observed disc spectrum. Numerical computation of the resulting spectrum is done using a convolution between a transfer function and the locally emitted spectrum. Plots showing spectral variations with viewing angle and colour encoded maps are produced to illustrate the effects.

Key words: accretion disc - general relativity - disc spectra
 
 
 
 

On The Modelling Of The Light - Time Effect

Alexandru Pop
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E-mail: andipop@usa.net

Abstract. A method for determination of preliminary elements of the light-time orbit in case of variable stars (both pulsating and eclipsing binary systems) belonging to binary systems is proposed.

Key words: variable stars - eclipsing binary systems - data analysis.
 
 
 

On The Prominence Formation In A Current Sheet - Some Numerical Experiments

Cristiana Dumitrache
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO - 75212 Bucharest, Romania
e-mail: crisd@roastro.astro.ro

Abstract. Three numerical simulations of prominence formations in a current sheet are presented. The effects of chromospheric mass injection (temporary or continuous) and of gravitation are taken into account.

Key words: prominence - current sheet - numerical simulations.
 
 
 
 

Short Time Indicators In The Restricted Problem Of Three Bodies

Zsolt Sandor (1), Robert Balla (2), Ferenc Teger (2), Balint Erdi (2)
(1) Konkoly Observatory of the Hungarian Academy of Sciences
H-1525 Budapest, P.O. Box 67, Hungary
(2) Department of Astronomy, Eötvös University
H-1117 Budapest, Pazmany Peter setany 1/A, Hungary

Abstract. We have applied the method of streching numbers (or local Lyapounov characteristic numbers), helicity and twist angles in order to distinguish between chaotic and regular domains of the restricted three-body problem. Comparing our results with the corresponding Poincaré's surface of section shows this method to be useful for a quick separation between regular and chaotic domains of the phase space. As we have shown in the case of the planar, circular and restricted three-body problem, the method of short-time indicators is very efficient and it needs only 20 iterations per orbit.

Key words: restricted three-body problem - Poincaré's surface of section - chaos indicator.
 
 

Lagrange-Jacobi And Sundman Relations In The Schwarzschild - De Sitter Model

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 n-body problem attached to the Schwarzchild - de Sitter field is being considered from the standpoint of the classical celestial mechanics. Relations analogous to the Lagrange-Jacobi equality and to Sundman's inequalities are proved to exist within the framework of this model, too.

Key words: celestial mechanics - n-body problem - relativistic fields.
 
 
 
 

On The Simultaneous Total Collapse In The Schwarzschild - De Sitter Field

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 study of the n-body problem in the Schwarzchild - de Sitter field is being continued. Based on an equality concerning the moment of inertia and on the Lagrange-Jacobi relation transposed for this model, the impossibility of the simultaneous total collapse in infinite time is proved.

Key words: celestial mechanics - n-body problem- relativistic fields - collision.
 
 
 
 

Special Families Of Orbits For The Henon-Heiles Type Potential

Mira-Cristiana Anisiu (1), Arpad Pal (2)
(1) " T. Popoviciu" Institute of Numerical Analysis of the Romanian Academy
P.O.Box 68, RO-3400 Cluj-Napoca, Romania
E-mail: mira@math.ubbcluj.ro
(2) "Babes - Bolyai" University, Astronomical Observatory,
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E-mail: apal@math.ubbcluj.ro

Abstract. For a Henon-Heiles type potential, with undetermined coefficients, the possibility for a material point to describe a family of curves of the form x^(-p)y = q is studied. Two admissible cases, p = 4 and p = -2, are found; for these the potential and the family boundary curves are specified, and the regions in which the curves of the given family can be traced are determined.

Key words: inverse problem - family boundary curves - Henon-Heiles potential.
 
 
 
 

About The Flash Period Of Artificial Satellites

Tiberiu Oproiu (1), Lucian Burs (2)
(1) Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E -mail: toproiu@email.ro
(2) Astronomical Institute of the Romanian Academy
Astronomical Observatory Timisoara
Piata Axente Sever 1, RO-1900 Timisoara, Romania
E-mail: lburs@astro.sorostm.ro

Abstract. A reduction method for photometric observations of artificial satellites is presented. A numerical application for the rocketbody of COSMOS 1250 is performed, the evolution of the spin period being pointed out.

Key words: artificial satellites - photometric observations.
 
 
 
 

Software For Computer Clock Correction

Liviu Serbanescu
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO-75212, Bucuresti, Romania
E-mail: livius@roastro.astro.ro

Abstract: The paper presents an utility software, made by us, for measuring the differences between the computer clok and the National Radio Station clock. This is necessary for CCD images acquisition.

Key words: timing - computer clock - radio clock signals.