ROMANIAN ASTRONOMICAL JOURNAL, VOL. 7, NO. 1, 1997
VASILE URECHE
University of Cluj-Napoca, Faculty of Mathematics and Computer Science
Str. M. Kogalniceanu 1, 3400 Cluj-Napoca, Romania
E-mail: vureche@math.ubbcluj.ro
Abstract. A method for constructing new classes of analytic stellar models is given, supposing that the product between the local values of gravitational acceleration and density is a known function of radius. As applications, three classes of models are considered.
Key words: astrophysics - stars - analytic models
GEORGETA MARIS, SIMONA DINULESCU
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212 Bucharest 28, Romania
E-mail: gmaris@roastro.astro.ro
Abstract. The authors set out to study the link between total solar irradiance (TSI), registering performed on ERB/NIMBUS 7 and some solar activity indices, during the minimum phase of the solar cycle (SC) 22 (1985-1987). The solar activity indices used are: the daily sunspot number (R), the radio flux on 10.7 cm (F), the coronal index in the green line (Ic), the daily scaled flare number (SFN) and the daily flare total area index (IfA). The results obtained prove the existence of a real correlation between the total solar irradiance variation and the solar activity phenomena of the active regions (sunspots, flares, radio emissions). It is also concluded that such a study is necessary to perform for a whole eleven-years solar cycle.
Key words: total solar irradiance - solar activity phenomena - eleven-years solar cycle
VASILE MIOC
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Ciresilor 19, 3400 Cluj-Napoca, Romania
E-mail: vmioc@roastro.astro.ro
CRISTINA STOICA
Institute for Gravitation and Space Sciences
Gravitational Research Laboratory
Str. Mendeleev 21-25, 70168 Bucharest, Romania
E-mail: cstoica@math.uvic.ca
Abstract. The Schwarzschild problem (i.e. the two-body problem associated to a potential of the form A/r + B/rl, where r = distance between particles, and A, B = real constants) is qualitatively tackled. The equations of motion are written in Hamiltonian formalism, and the first integrals of energy and angular momentum are pointed out. Using McGehee's transformations, the motion equations are regularized, and the collision singularity is replaced by the collision manifold. The flow on this manifold is described. Analogously, one introduces the infinity manifold (corresponding to r tending to infinity), and one characterizes the respective flow.
Key words: celestial mechanics - Schwarzschild problem - McGehee transformations
DAN SELARU
Institute for Gravitation and Space Sciences
Laboratory for Gravitation
Str. Mendeleev 21-25, 70168 Bucharest, Romania
E-mail: dselaru@usa.net
Abstract. The applicability domain of Levi-Civita and Kustaanheimo-Stiefel transformations is extended by considering a more general family of Hamiltonian functions on which these transformations can be applied. The action-angle variables are being obtained, as well as two other sets of canonical variables.
Key words: celestial mechanics - Hamiltonian dynamics - Levi-Civita and Kustaanheimo-Stiefel transformations - action-angle variables
GHEORGHE VASS
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212, Bucharest 28, Romania
E-mail: gvass@roastro.astro.ro
Abstract. The paper presents a method of accuracy analysis for the CCD positions, used for the rejection of the erroneous positions.
Key words: CCD astrometry - planetary satellites
GHEORGHE VASS
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, 75212, Bucharest 28, Romania
E-mail: gvass@roastro.astro.ro
Abstract: The paper presents the CCD positions obtained in Bucharest during PHESAT'95 for the satellites of Saturn.
Key words: CCD astrometry – Saturn - planetary satellites - PHESAT'95