CCD OBSERVATIONS ON GP ANDROMEDAE. I: OBSERVATIONAL DATA BETWEEN 2003–2005
VLAD TURCU,
Alexandru pop,
dan
moldovan
Astronomical
Institute of the
Astronomical
Observatory Cluj-Napoca
Str.
Cireşilor
19, 400487 Cluj-Napoca, Romania
E-mail:
vladturcu@yahoo.com
Abstract. In this paper we
present 2625 new CCD observations on the HADS
star GP Andromedae performed between 2003 and 2005 in
Johnson V filter. All the
obtained light curves were analyzed using the Fourier decomposition
technique,
and the corresponding structural parameters
were computed.
Key words: variable stars – high-amplitude δ Scuti stars – data analysis.
LIGHT-CURVE ADJUSTING WITH CUBIC SPLINE FUNCTIONS
DAN MOLDOVAN
Astronomical
Institute of the
Astronomical
Observatory Cluj-Napoca
Str.
Cireşilor
19, 400487 Cluj-Napoca, Romania
E-mail:
dnmoldovan@gmail.com
Abstract. The present paper
deals with light-curve fitting by a piecewise
cubic polynomial which is continuous with its first derivatives.
We perform an
application to fitting two light curves of high-amplitude: the δ Scuti
star GP
Andromedae, and a mutual event of Jupiter’s
Galilean satellites.
Key words: cubic spline functions – light curves – high-amplitude δ Scuti star – planetary satellites – mutual events.
INVESTIGATION OF
THE HALO (I)CME
OBSERVED
ON
IULIA CHIFU 1, ADRIAN ONCICA 1, MARILENA MIERLA 1,2,
GUADALUPE MUÑOZ-MARTÍnez 3, CRISTIANA
DUMITRACHE 1
1 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
[iulia, adrian,
marilena, crisd]@aira.astro.ro
2 Royal
Observatory of
3 Escuela
Superior de Ingenieria Mecánica y Eléctrica, Campus
Zacatenco,
IPN
Abstract. We investigate
the characteristics of a halo CME that arrived at
Earth and produced a geomagnetic storm. Using data
from few satellites (
Key words: solar physics – halo CME – geomagnetic storm.
GROUPS OF SYMMETRIES IN LENNARD-JONES-TYPE PROBLEMS
VASILE MIOC 1, EMIL
POPESCU 2,
NEDELIA ANTONIA
POPESCU 1
1 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
vmioc@aira.astro.ro,
nedelia@aira.astro.ro
2 Technical University of Civil Engineering
Bd.
Lacul Tei 124, 020396
E-mail:
epopescu@utcb.ro
Abstract.
We consider the
astronomical connotations of the famous Lennard-Jones potential. To go
deeper
into the study of the two-body
problem associated to this model (Mioc et al. 2008),
we provide a general view on the symmetries that characterize the
problem. In
Cartesian
or standard polar coordinates, as well as in collision-blow-up and
infinity-blow-up McGehee-type coordinates, these symmetries form
isomorphic
(even diffeomorphic in three cases) 8-element Abelian groups with
idempotent
structure. Every one of them owns seven proper 4-element subgroups,
isomorphic
to Klein’s group. In Levi-Civita coordinates, we obtain a 16-element
Abelian
group of symmetries with idempotent structure, which
owns thirty-five 4-element
subgroups isomorphic to Klein’s group.
Key words: celestial mechanics – two-body problem – Lennard-Jones potential – symmetries.
ON
A CLASS OF
EQUILIBRIA OF
A SMALL RIGID
BODY IN
A
TILEMAHOS KALVOURIDIS
Zografou
Campus GR 157 73,
E-mail:
tkalvouridis@gmail.com
Abstract. A class of equilibrium states of a small tri-axial rigid
body acted
upon by the Newtonian forces of two major bodies of spherical
symmetry and
equal masses is studied in this paper. The equations of the
translational-rotational motion of the minor body are derived and its
equilibrium states as well as their stability are investigated.
Key
words: rigid body dynamics –
THE GYLDÉN-TYPE PROBLEM: RESONANCES AND CHAOTICITY
CATALIN CUCU-DUMITRESCU 1, VASILE MIOC 2, DAN ŞELARU 1
1 Institute for Space Sciences
Şos.
Atomiştilor 409,
E-mail:
cucudumitrescu@yahoo.com,
danselaru@yahoo.com
2 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
vmioc@aira.astro.ro
Abstract. We tackle the
Gyldén-type problem (a two-body problem with
time-changing equivalent gravitational parameter). For one of the most
interesting cases for astronomy (small-amplitude periodic variation),
we study
the behavior of the system in the neighborhood of resonances. Two
important
issues are pointed out: circular orbits are not possible, and capture
in
resonance is not possible. As another noticeable result, a partial
averaging of
the vector field, combined with the introduction of a slow timelike
variable,
leads to a one-degree-of-freedom system of ODE.
Considering the simplest case
of the variation, we perform some numerical experiments. Even in the
simplest
case, the phase portraits are very
complex: a mixture of oscillation zones,
circulation zones, and chaotic zones. The chaoticity extends as the
angular
momentum and the small
parameter that features the problem grow.
Key words: celestial mechanics – nonlinear particle dynamics – Gyldén-type problem – resonances – chaoticity.