The Study Of The Galaxies Clustering In The Field of the Quasar B2 1335+28

Nedelia Antonia Popescu, Marian Doru Suran
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint, RO-75212 Bucharest 28, Romania
E-mail: delia@roastro.astro.ro, suran@roastro.astro.ro

Abstract. In this paper we use the optical and near infrared photometrical data for the significant clustering of galaxies around the radio-loud quasar B2 1335+28, at redshift z = 1.086 (Tanaka et al. 2000), and the PEGASE spectral evolution model of galaxies ( Fioc and Rocca -Volmerange 1996) in order to study the morphology and color evolution of galaxies. By means of the photometric redshifts technique (Gwyn 1999) we determine the galaxies morphology and redshifts, finding a peak around z = 1.1 in the photometric redshifts distribution.

Key words: cosmology - galaxies clustering- photometric redshifts - color evolution of galaxies.
 

Bremsstrahlung Emission From A Complex Distribution Of Electrons

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

Abstract. The spacecraft observations in the heliosphere have proven that shocks can accelarate particles with high efficiency, out of the superthermal range of energies. Energetic particles exist everywhere in the universe and shocks are commonly associated with them. We pay attention to the model of diffusive shock acceleration for electrons. We compute the continuumbremsstralung emission of a complex distribution  of electrons from  thermal to highest energies.

Key words: diffuse shock acceleration - non-thermal bremsstralung - Maxwellian distribution- acceleration of particles.
 

On The Multiperiodicity Of The Orbital Period Variation Of ST Persei

Alexandru Pop (1), Victor Liteanu (2), Cosmin Pavel (1)
(1) Astronomical Institute of the Romanian Academy
Astronomical Observatory of Cluj-Napoca
Str. Ciresilor 19, RO-3400 Cluj-Napoca, Romania
E-mail: apop@academie.cj.edu.ro
(2) Babes-Bolyai University
Faculty of Chemistry and Chemical Engineering
Str. Arany Janos 11, RO- 3400 Cluj-Napoca, Romania

Abstract. The period variation of the Algol-type binary system ST Persei is resumed on the basis of 245 minimum light times covering a time base of 91.3 yr. The multiperiodic character of its O-C curve is confirmed. It could be caused by the superposition of a long periodicity (67.9 yr) corresponding to the orbital motion related to an unseen companion and a short one (23.82 yr), possibly due to cyclic magnetic activity of the secondary component in the system. The Gaussianity of the final O-C residuals is investigated through tests chi, Kolmogorov and Wilcoxon.

Key words: binary stars - orbital motion -multiperiodicity.
 

Apsidal Motion In Some Eclipsing Binaries
 
Valeriu Tudose (1), Alexandru Dumitrescu (2), Mircea Rusu (1)
(1) Faculty of Physics, Univeristy of Bucharest
Str. Atomistilor 1, Bucharest-Magurele, Romania
E-mail: mrusu@yahoo.com
(2) Astronomical Institute of the Romanian Academy,
Str. Cutitul de Argint 5, RO- 75212 Bucharest , Romania
E-mail: alex@roastro.astro.ro

Abstract. In this paper we calculate the apsidal motion rate for three early-type eclipsing binary systems: AG Per, EK Cep and Y Cyg. From the apsidal period, we determine the internal structure constant (ISC). For the analysis we have used all the times of minimum light accessible to us from literature.

Key words: close binaries - apsidal motion.
 
 

H-Alpha Solar Observations With A CCD Camera

Eugen-Catalin Matei
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO- 75212 Bucharest, Romania
E-mail: catalin@roastro.astro.ro

Abstract. This paper presents the image acquisition technique by CCD for chromospheric observations with a SBIG ST-7 CCD camera through a H-alpha filter using the PC. It also presents some image acquisition problems.

Key words: CCD - H-alpha solar observations.
 
 

Contributions Of The Bucharest Observatory To The CONFOR Program

Gheorghe Bocsa
Astronomical Institute of the Romanian Academy
Str. Cutitul de Argint 5, RO- 75212, Bucharest 28, Romania
E-mail: gbocsa@roastro.astro.ro

Abstract: The connection between the optical reference frame and the radio one constitutes one of the main purposes of the astrometry. The paper is pointing out the contribution of the Bucharest Observatory in this direction. The statistic analysis of the standard errors for the astrometric PPM and TYCHO stars is presented.

Key words: photographic astrometry - reference systems - catalogues.
 
 

A Solvable Version Of The Direct Problem Of Dynamics

George Bozis (1), Mira-Cristinana Anisiu (2), Cristina Blaga (3)
(1) University of Thessaloniki, Department of Theoretical Mechanics
54006 Thessaloniki, Greece
E-mail: gbozis@ccf.auth.gr
(2) Romanian Academy, " T. Popoviciu" Institute of Numerical Analysis
P.O. Box 68, RO-3400 Cluj-Napoca, Romania
E-mail: mira@ictp-acad.ubbcluj.ro
(3) 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. Given any two-dimensional potential V(x,y), we find (if there exists, of course) without integration of the pertinent equation of motion a monoparametric family of orbits of the form f (x,y) = y + h(x) =c (whose members are shifted paralelly to the y-axis) traced by a unit mass material point.The main tool to this end is the non-linear second order partial differential equation of the inverse problem of Dynamics (Bozis, 1995). In general, a condition on the given potential is derived: in case this condition is fulfilled, the function gamma can be obtained as the common root of two polynomial equations. In certain particular cases (isotach orbits, one-dimensional potentials) the differential equations become ordinary and the solution is found to completion in a different manner.

Key words: monoparametric family of orbits - direct and inverse problem - isotach orbits.
 
 

Collision And Escape Dynamics In Fock's 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 two-body problem associated to the classical field corresponding to Fock's relativistic model is being tackled. The singularity at the origin is blown up, via a sequence of McGehee-type transformation, and replaced by a manifold pasted on the phase space; one obtains in this way regular equations of motion and first integrals. The local flows on the collision manifold and in its neighbourhood are being described. To study the motion very far from the field source, one introduces the so-called infinity manifold. After using a second set of McGee-type transformations, the local phase protraits on the infinity manifold and in its neighbourhood are being depicted.

Key words: celestial mechanics- relativistic fields - McGehee transformations - collision - escape.
 

Singularities Of The Two-Body Problem Associated To Quasihomogeneous Potentials Are Collisions

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 nature of singularities in the two-body problem associated to quasihomogeneous potentials is being tackled. Both the traditional and Painleve's necessary and sufficient conditions for singularities (valid in the Newtonian case) are transposed in the quasihomogeneous case. All such singularities are proved to be due to collisions.

Key words: celestial mechanics- two-body problem - quasihomogeneous potentials - collisions.