ROMANIAN ASTRONOMICAL JOURNAL
Vol. 20, No. 2, 2010
C O N T E N T S
|
Cristiana
DUMITRACHE, Nedelia Antonia POPESCU,
A Ulysses
ICME Event ind its Track Back to the Sun
|
97106
|
|
Badaoui ELMABSOUT,
Michael BARBOSU,
Relative
Equilibrium Configurations in the Three-Body Problem: Two Rigid Bodies and
a Mass Point
|
107145
|
|
Ioannis Iraklis
HARANAS, Vasile MIOC,
Quantum Corrections to the Gravitational Potential and Orbital
Motion
...
......
.
|
147156
|
|
Ciprian CHIRUTA,
Tiberiu OPROIU,
Artificial
Satellite Nodal Period under Poyting-Robertson Effect. I. Method and Preliminary
Results
..
|
157166
|
|
Dan MOLDOVAN,
Vlad TURCU, Tiberiu OPROIU,
X-splines
- Applications in Astronomy
..
|
167173
|
|
Vlad TURCU,
Dan MOLDOVAN, Alexandru POP,
PHEMU 2009
and PHESAT 2009 Campaigns: Timing Data Obtained at Cluj-Napoca Astronomical
Observatory
|
175184
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
MEAN DENSITIES OF NEUTRON STARS
VASILE URECHE
1, RODICA ROMAN
2
1 Babeş-Bolyai University of Cluj-Napoca
Str. M. Kogγlniceanu 1, 400084 Cluj-Napoca, Romania
E-mail: vureche@math.ubbcluj.ro
2 Astronomical Institute of the
Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Cireşilor 19, 400487 Cluj-Napoca, Romania
E-mail: rdcroman@yahoo.com
Abstract.
For a spherical neutron star the proper (relativistic) volume is computed.
Then, by using Douchin-Haensel equation of state, the mean densities of
neutron stars were obtained. So, different characteristics of neutron stars
can be represented as functions of mean density, instead of central density.
The concentration of matter towards the center of star is a decreasing function
of central density or, alternatively, a decreasing function of dimensionless
central pressure, for stable configurations. This means that the most compact
neutron stars tend to become closer to homogeneous objects.
Key words:
stellar structure neutron stars.
LONG-TERM ORBITAL PERIOD
VARIATION
OF RT ANDROMEDAE
ALEXANDRU POP, RODICA ROMAN
Astronomical Institute of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Cireşilor 19, 400487 Cluj-Napoca, Romania
E-mail: andi_pop@yahoo.com,
rdcroman@yahoo.com
Abstract. Different
authors approached the problem of orbital period variation of the active
eclipsing binary RT Andromedae on long time scales. Some of them suggested
the presence of a periodicity longer than 100 years. Such a conclusion encounters
an important difficulty: the inferred periodicity is longer than the time
base of the available data. We tackled this problem using visual, photographic,
and photoelectric times of minimum light.
Key words:
variable stars eclipsing binary systems data analysis.
MODELING FLUCTUATIONS
OF SOLAR
WIND PARAMETERS
WITH HEAVY-TAILED DISTRIBUTIONS
EMIL POPESCU 1,2, NEDELIA ANTONIA POPESCU 1
1 Astronomical Institute of the
Romanian Academy
Str. Cuţitul de Argint 5, 040557 Bucharest, Romania
E-mail: nedelia@aira.astro.ro
2 Technical University of Civil
Engineering
Bd. Lacul Tei 124,
020396 Bucharest, Romania
E-mail: epopescu@utcb.ro
Abstract. Recent approaches for heavy-tail time series models
are applied to the study of the statistical properties in solar wind turbulence.
We investigate the probability distribution functions (PDFs) of fluctuations
for solar wind plasma parameters and interplanetary magnetic field, for
in-situ data recorded by Ulysses during 2001. The scale dependence of the
observed PDFs for velocity, and magnetic field intensity fluctuations are
well fitted for different time lags using multi-scale statistical methods.
Analysis of the magnetic field strength shows that these fluctuations are
less intermittent at larger scales than at small scales, their behavior at
different scales being quantitatively described by the PDFs.
Key words:
solar wind turbulence solar wind plasma parameters interplanetary magnetic
field probability distribution function intermittent behavior.
ACTIVE REGION 9612 EVOLUTION
LILIANA DUMITRU, CRISTIANA DUMITRACHE
Astronomical Institute
of the Romanian Academy
Str. Cuţitul de Argint 5, 040557 Bucharest, Romania
E-mail: lyly@aira.astro.ro,
crisd@aira.astro.ro
Abstract.
The active region 9612 was observed between 6 and 17 September 2001. Situated
in the Northern hemisphere of the Sun, this region is closely linked to
a filament evolution, forming together an interesting magnetic topology.
We analyze the evolution of this active region and the explosive events that
occurred during this period: the flares on 13 and 16 September, and a CME
on 15 September 2001. We use ground-based observations and data from space
(SOHO, Yohkoh).
Key words:
Sun active regions filaments magnetic fields CMEs.
KINK INSTABILITIES TRIGGERING
A FILAMENT ERUPTION
CRISTIANA DUMITRACHE, DIANA CONSTANTIN
Astronomical Institute
of the Romanian Academy
Str. Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail: crisd@aira.astro.ro,
diana@aira.astro.ro
Abstract.
A huge complex filament was observed between 28 December 2000 and 7 January
2001. We analyze its dynamics and its sudden disappearance. We analyze the
3D coronal magnetic field extrapolated from the MDI photospheric magnetograms
and compare with filament coronal images. The filament erupted in a CME
after a mild helical upward movement of plasma on 7 January. We attempt to
explain this CME event onset by kink instabilities. An approach to estimate
the filament helicity and magnetic flux injection explain the filament destabilization.
Key words:
Sun prominences CMEs instability.
OBLIQUE PROPAGATION AND
DISSIPATION
OF ALFVΙN WAVES IN CORONAL HOLES REINVESTIGATED
SURESH CHANDRA 1, LALAN PRASAD 2
1 School of Physics, Shri Mata Vaishno
Devi University
Katra 182 320 (J&K), India
E-mail: suresh492000@yahoo.co.in
2 Department of Physics, M.B. Govt.
P.G. College
Haldwani 263 241, India
Abstract.
We have reinvestigated the work on oblique propagation and dissipation
of Alfvιn waves in coronal holes. Srivastava and Dwivedi
(2007) derived a dispersion relation for oblique propagation of Alfvιn waves.
This relation seems to be erroneous. Consequently, the conclusions formulated
by them are not reliable.
Key words:
solar physics coronal holes Alfvιn waves.
THE LIE-INTEGRATOR
AND THE HΙNON-HEILES SYSTEM
IHARKA SZάCS-CSILLIK
Astronomical Institute
of the Romanian Academy
Astronomical Observatory Cluj-Napoca
Str. Cireşilor 19, 400487 Cluj-Napoca, Romania
E-mail: iharka@gmail.com
Abstract. There
are several integration schemes intended to solve the equations of
motion in problems of celestial mechanics. The Lie-integration method is
based on the idea to tackle systems of ODE via Lie series. It is applied
to solve Hamiltonian systems by giving recurrence formulae for the calculation
of the Lie-terms. Here we present these recurrence formulae, which considerably
simplify the linearized equations of motion. To exemplify, we choose the
famous chaotic Hιnon-Heiles system. Then the Lie-integrator is compared with
the well-known Runge-Kutta method and the symplectic integrator for the
Hιnon-Heiles system. The convergence of the
Lie-integrator can be regarded as a kind of a symplectic integrator, which
conserves the integrals of motion. The Lie-integrator method is found to
be very well suited for a long-time integration of orbits in celestial mechanics.
Key words:
celestial mechanics numerical methods Lie series Hιnon-Heiles model.
QUANTITATIVE AND QUALITATIVE
ANALYSIS
OF GEOSTATIONARY SATELLITE DYNAMICS
ADRIAN DRǍGUŞAN
Naval Academy Mircea
cel Bătrβn, Constanţa, Romania
Abstract.
This paper presents a quantitative and qualitative analysis of geostationary
satellite motion. This analysis is included in the doctoral thesis of the
author, sustained in September 2009. The numerical results are well known
and they are found in many scientific works. We use an original method,
based on Runge-Kutta 4th order, in order to obtain the separate effect of
each perturbation on the orbit of the geostationary satellite. The satellite
will be launched soon by South Korea at 128 degrees longitude. The qualitative
approach is first time used to analyze the orbital motion of the geostationary
satellite.
Key words:
geostationary satellites qualitative analysis.
DCRF-ICRF CONNECTION
AND ASTEROID DIFFERENTIAL ASTROMETRY
ALIN NEDELCU 1, PETRE POPESCU 1, Octavian bǍdescu 1,2,
PETRE PARASCHIV 1
1 Astronomical Institute of the
Romanian Academy
Str. Cuțitul de Argint 5, 040557 Bucharest, Romania
E-mails: [nedelcu,
petre, octavian, paras]@aira.astro.ro
2 Technical University of Civil
Engineering, Faculty of Geodesy
Bd. Lacul Tei 124,
020396 Bucharest, Romania
Abstract.
One of the methods used to obtain an accurate tie between the different
reference frames is the simultaneous observation of an object referred to
both frames. In our case, in which we investigate the link between dynamical
reference frame and ICRF, this method will require CCD imaging of an asteroid
and of an angular nearby quasar. The direct comparison of the asteroid position
obtained from a dynamical model of the Solar System with the quasar optical
position in an optimally calibrated astrometric field will yield the local,
instantaneous orientation of the dynamical celestial reference frame (DCRF)
with respect to a quasi-inertial, extragalactic reference frame. We present
a database of apparent close approaches between asteroids and quasars, events
that could be used to investigate the DRF-ICRF link.
Key words:
astrometry reference frames asteroids.
A PROJECT FOR MODERN
ASTROGEODETIC
GEOID DETERMINATION
Octavian bǍdescu 1,2, marin Plopeanu 2, ALIN NEDELCU 1,
PETRE POPESCU 1, PETRE PARASCHIV 1
1 Astronomical Institute of the
Romanian Academy
Str. Cuțitul de
Argint 5, 040557, Bucharest, Romania
E-mails: [octavian,
nedelcu, petre,paras]@aira.astro.ro
2 Technical University of Civil
Engineering
Bd. Lacul Tei 124,
020396, Bucharest, Romania
E-mail: mplopeanu@geodezie.utcb.ro
Abstract.
Nowadays, astrogeodetic methods for geoid determination are often considered
obsolete. We present in this paper a new project for geoid determination
by astrogeodetic vertical deviation, based on state-of-the-art geodetic and
astronomical technologies. Our proposal tracks the accuracy and efficient
real time determination of the vertical deviations, in sufficient number
points, which will serve to the geoid determination. This project is designed
as collaboration between the Bucharest Technical University of Civil Engineering,
Faculty of Geodesy, and the Astronomical Institute of the Romanian Academy,
Fundamental Astronomy Department.
Key words:
astrogeodesy geoid vertical deviation.
125 YEARS SINCE THE BIRTH OF THE ASTRONOMER
GHEORGHE DEMETRESCU (18851969)
DOINA IONESCU
Astronomical Institute
of the Romanian Academy
Str. Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail: doinaionescu36@clicknet.ro
Abstract.
We survey the life and work of Academician Gheorghe Demetrescu, renowned
Romanian astronomer, at the 125th anniversary of his birth. We point out
especially his activity as a professor and as the Director of the Bucharest
Astronomical Observatory.
Key words:
history of astronomy Bucharest Astronomical Observatory.