EXTREMELY RED OBJECTS

AROUND THE RADIO-LOUD QUASAR B2 1335+28

NEDELIA ANTONIA POPESCU, MARIAN DORU ?URAN

Astronomical Institute of the Romanian Academy

Str. Cu?itul de Argint 5, RO-75212 Bucharest, Romania

E-mail: delia@aira.astro.ro, suran@aira.astro.ro

Abstract. Using the optical and near infrared photometrical data for the objects in the field of the radio-loud quasar B2 1335+28, at redshift z = 1.086 (Tanaka et al. 2000), we determine the sample of the Extremely Red Objects (EROs) in this field. We analyze the K-band galaxy number counts, the colors distributions, the surface density and the radial density profiles for the entire sample of galaxies and for these special objects, searching for radial trends and features of clustering. In the studied field is observed a 3 times increased surface density of EROs, selected with different single-color criteria, in comparison with the density of such objects in the general field. This result confirms the presence of an overdensity of galaxies with red colors in the neighbourhood of the quasar, representing a cluster of galaxies.

Key words: cosmology – color evolution of galaxies – extremely red objects.
 
 
 
 
SAKHAROV'S TEMPERATURE LIMIT

IN A MODIFIED SCHWARZSCHILD METRIC

IOANNIS IRAKLIS HARANAS

Department of Physics and Astronomy

York University, Toronto, Ontario, Canada

E-mail: ioannis@yorku.ca

Abstract. In this paper we are going to examine the effect, if any exists, that a modification of the Schwarzschild metric by a lambda term could have on the so-called Sakharov’s upper temperature limit. It’s known that Sakharov’s limit is the maximum possible black-body temperature that can occur in our universe.

Key words: cosmology – Schwarzschild metric – cosmological constant – Sakharov's limit.
 
 
 
 
 
 
 
 
 
 
A SOLAR ACTIVITY FORECAST:

CYCLES 23–26

MIROSLAV MIKULECKÝ 1, JAROSLAV STREŠTÍK 2

2 Institute of Preventive and Clinical Medicine

Bratislava, Slovak Republic

E-mail: mikuleky@upkm.sk

2 Geophysical Institute of the Academy of Sciences of the Czech Republic

Prague, Czech Republic

E-mail: jstr@ig.cas.cz

Abstract. Increasing interest in putative effects of the changing solar activity on the Earth including biomedical and sociological events actualizes the need for forecasting its behaviour in the future. The authors demonstrate an inferential statistical way of forecasting sunspot relative numbers four decades ahead. Their prediction for 1961–1995, based on the 1500–1960 data and confronted with the known observations in this interval, was better than that based on 1910–1960, 1749–1960, and 1849–1960 data. The proper forecast for 1997–2040 was therefore constructed from the 1500–1996 data.

Key words: sunspot forecast – inferential statistics.
 
 
 
 
SYMMETRIES IN THE ANISOTROPIC

KEPLER PROBLEM

VASILE MIOC

Astronomical Institute of the Romanian Academy

Str. Cu?itul de Argint 5, RO-75212 Bucharest, Romania

E-mail: vmioc@aira.astro.ro

Abstract. The two-body problem associated to an anisotropic Newtonian-type potential function is being considered. We point out the complex symmetries that feature this problem. Such symmetries, expressed in standard polar coordinates, are recovered for McGehee-type coordinates of both collision-blow-up kind and infinity-blow-up kind. They form isomorphic commutative groups endowed with an idempotent structure. Expressed in Levi-Civita's coordinates, the problem exhibits a larger group of symmetries, also commutative and endowed with an idempotent structure.

Key words: celestial mechanics – anisotropy – symmetries.
 
 
 
 
THE DARK MATTER PERTURBATION

OF THE TWO-BODY PROBLEM

C?T?LIN CUCU-DUMITRESCU, DAN SELARU

Institute for Space Sciences

Str. Mendeleev 21-25, Bucharest, Romania

E-mail: cucudumitrescu@yahoo.com

Abstract. The notion of WIMPs (Weakly Interacting Massive Particles) is used in modern Physics to define a class of particles, which do not interact electromagnetically, but only gravitationally. WIMPs can be found in the neighbourhood of a massive celestial body (star, planet), forming a cloud of low-density matter (dark matter), which can be modeled as a continuous medium. In such a mechanical system, the motion of a test particle is perturbed by the interior potential of the WIMP cloud. The first problem we focused on is the possibility of obtaining a particular type of perturbation due to the WIMP cloud, in order to explain some corrections of the universal law of attraction. The well-known Maneff correction (for the motion of Mercury around Sun) can be obtained in this way, if we admit the presence of a certain low-density cloud in the vicinity of Mercury's orbit. The main issue of this paper is the description of the motion of a test particle around a massive celestial body surrounded by a spherical, uniformly dense WIMP cloud. We obtained two forms of first order solution, taking the density of the cloud as a small parameter; the first form is clearly intuitive and the second one is proper for the numerical investigations of close approach orbits.

Key words: celestial mechanics – dark matter – perturbed two-body problem – canonical transformations.
 
 
 
 
EQUILIBRIA OF CONSTANTIN POPOVICI'S

PHOTOGRAVITATIONAL MODEL REVISITED

VASILE MIOC

Astronomical Institute of the Romanian Academy

Str. Cu?itul de Argint 5, RO-75212 Bucharest, Romania

E-mail: vmioc@aira.astro.ro

Abstract. The equilibria of the two-body problem associated to Constantin Popovici's photogravitational model are tackled again. We consider the motion in the infinity-blow-up coordinates provided by McGehee-type transformations. Then we study the vector field expressed in collision-regularizing Levi-Civita coordinates. This new framework provides the same location of the equilibria and the same information about their nature as the previous approaches.

Key words: celestial mechanics – photogravitational fields – qualitative analysis – equilibria.
 
 
 
 
ACCURATE POSITIONS FOR THE ASTEROID

433 EROS IN 1935–1938 AND 1972–1975

GHEORGHE BOC?A, CONSTANTIN TELEANU

Astronomical Institute of the Romanian Academy

Str. Cu?itul de Argint 5, RO-75212 Bucharest, Romania

E-mail: gbocsa@aira.astro.ro, teleanu@aira.astro.ro

Abstract. The present paper joins the astrometric efforts to determine precise positions for the asteroid 433 Eros. The observations have been performed with a 380/6000 mm astrograph, in the intervals 1935–1938 and 1972–1975. Both methods: Turner (constants) and Schlesinger (dependencies) were used for the computation of the normal coordinates of the asteroid.

Key words: astrometry – 433 Eros.