Solar Physics Variable Stars Extragalactic Astronomy and Cosmology Astrometry Celestial Mecanics History of Astronomy
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VARIABLE STARS
Three groups from Bucharest, Cluj-Napoca and Timisoara are working to the project “Observational Study of Variable Stars and their Theoretical Modelling”. The main directions of investigation were focused on the light curve observation and interpretation of eclipsing binary stars and Delta Scuti type stars. The most important results obtained in this research field are as follows:
Using the observations carried out at Bucharest Observatory in 2004, the first ground-based photoelectric light curve of eclipsing binary V 376 And was obtained. V 376 And is a new variable star discovered by HIPPARCOS mission.
From HIPPARCOS data, the first elements were secured for the newly discovered eclipsing binary HIP 64528.
Utilizing the proper photoelectric observations (the first ones from the ground) performed at Bucharest Observatory during 1999–2001, the first elements of the eclipsing binary VW LMi were obtained.
There were performed studies concerning the short and long
time scale
variability in the light curves of the high-amplitude Delta Scuti type
stars DY Peg and GP And. Studies on the use of pulse position
modulation
theory in study of periodic variability phenomena were also carried
out.
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EXTRAGALACTIC ASTRONOMY AND COSMOLOGY Due to the new supercomputation system ALTIX 350 (24Gflops , 4 proc./1.3GHz/1.5Mb L2, 12Gb RAM, 250Gb HDD), acquired by the Astronomical Institute, the package of cosmological simulations was restored and we passed on to the phase of very high resolution simulations using methods of the parallelization and vectorialization of the super calculus processes.
The cosmological simulations were modified and tested for various scenarios: LCDM, CHDM, CDM, variants of N-body PM-type (unifluid) and P3M (bifluid baryonic DM+SPH). These simulations were spatially improved by ART-type methods.
We intend to determine the structures at large scale (LSS, R=1000h**-1 Mpc), medium scale (MSS, R=100h**-1 Mpc) and small scale (LocSS, R=1-10h**-1 Mpc).
By means of our own ALTIX 350 system we made simulations of N-bodies for 512**3 bodies on grids of 1024**3 zones.
Using a GRID distributive system between our own ALTIX 350 system and the ALTIX system of 12 processors of the SGI/USA we managed to improve 8 times both the grid resolution and the massic one (1024**3 corpuri/2048**3 zone).
The space and masses resolutions thus attained allowed the building of new soft packages in order to determine different structures and their evolution:
- the filamentary structures at the LSS level;
- the galactic halos at the LSS, MSS, LocSS levels,
- the two-point correlation function at LSS level;
- the parental and descending hierarchic organization at the LSS, MSS, LocSS levels;
- the interactions of types filament-filament, filament-halo, halo-halo and halo-interhalos environment;
- the gas distribution at the MSS and LocSS levels;
- the study of gas distribution and of formation and evolution of protostars, stars and satellite stellar systems in galaxies (MSS->LocLSS).
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ASTROMETRY
There were continued, in cooperation with the Astronomical Observatories of Kiev and Nikolaev, Ukraine, the studies concerning the reference stars to be used for extra-galactic radio-sources. The contribution of the Astronomical Institute concerns in the observation the optical parts of ICRF sources and the elaboration of the intermediary reference catalogue. In the field of balcanic cooperation, we started astronomical observations (October 2004) with 60 cm Zeiss Telescope in Belogradchik, Bulgaria. The first observations are very good quality ones and involves all new detection devices. In the next year, we planned to observe all the sources with magnitudes < 22 from northern hemisphere. These observation are connected with observations performed in Bucharest with our modernized 6000/380 Prin astrograph.
The studies concerning the determination of the vertical deviation were continued by publishing articles and two chapters of a book.
As regards the Solar system astrometry, the observations concerning Neptune and minor planets were completed. The computation programe is build to improve orbital elements of the asteroid and it was finalised an application of this programe. We processed the plates containing positions of Neptun and an article was proposed. It was observed CCD and in photographic mode the transit of Venus. We observe also a number of two PHA’s, our contribution is mentioned on the site:
http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?sites:073;obs;1;200
The observational results contained in the plate archive were studied, in order to adapt standards and non-standards techniques for image processing in order to obtain useful information. We devellopped a new model for the storage of the information contained in digitized plates. We establish a first mechanism to connect plate information with the contents of a general catalogue and we will identify the objects from digitized plates to create a consistent generalised system of information.
ASTROGRAPH
(38/600 cm) (38/600 cm)
The
Prin-Merz double astrograph has an objective of 38 cm diameter and 600
cm focal
length. Photographic plates of 24 x 24 cm are used; the instrument has
a field
of 2° x 2°. The plates are measured on an Ascorecord machine
(0.1). An Apogee
47p camera was attached in 2004 to the optical telescope. For accurate
pointing, on the finder is mounted a Mintron CCD camera.
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CELESTIAL MECHANICS
The
study of Manev model was continued. The specific features of the
corresponding
two-body problem were synthesized. We also investigated the
photogravitational
restricted three-body problem in a Manev-type field, establishing the
characteristics
of the librations points. The Popovici-Manev photogravitational model
was
tackled from standpoint of symmetries.
Symmetries
of the vector field that characterizes the Mücket-Treder two-body
problem were
pointed out and studied, too.
Continuing
the study of the anisotropic Schwarzschild-type problem, we used
variational
methods to prove the existence of symmetric periodic orbits (a proof
that we
were not able to provide in 2003). Applying these results to concrete
astronomical situations, we emphasized the existence of such
trajectories in
proto-stellar systems or around stars with spots.
The
two-body problem associated to celebrated Hénon-Heile’s model
was studied as
regards near-escape dynamics. Exotic features were pointed out, which
need a
deeper digging intended to clarify the origin of two presumed
bifurcations.
The
two-body problem in the point-mass (or gravito-elastic) field, tackled
in 1999,
was completed by a fifth paper, which describes the global flow.
We
went deeper in the PPN (1+2)-problem by splitting it into two 2-body
problems
and offering the theoretical basis for a GRT experiment.
We
investigated the stability of equatorial satellite orbits around
nonspherical
planets, finding only a zero-Lebesgue-measure set of initial conditions
that
lead to instability.
The
possible connections between solar activity and Earth’s rotation (a
largely
discussed problem during the last years) was tackled by us, too. We
identified
two possible correlations with 26-month and 11-year solar cycles.
All
these results were presented at international astronomical meetings and
were
published in Romanian and foreign journals (see Publications).
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HISTORY OF ASTRONOMY
At the 24th IAU General Assembly, a communication was presented concerning the storing of astronomical information on the Romanian territory. This was the departure point for an idea: to set up of a databank intended to include all testimonies of archaeoastronomical knowledge in the South-Eastern European region.
The contribution of Constantin C. Popovici (1878-1956) to the
Romanian
astronomy, by both the direction of two observatories (Jassy and
Bucharest)
and an original photogravitational model, was emphasized, too.
.