REAL SIZE AND
MEMBERSHIP RICHNESS
DETERMINATION OF HIGH-LATITUDE
OPEN CLUSTERS
ASHRAF LATIF
TADROSS
National
Research Institute of Astronomy and
Geophysics
11421-Helwan,
Cairo, Egypt
E-mail:
altadross@mailer.eun.eg
Abstract. We use proper
motion measurements to determine the real size and
membership richness of a sample of open clusters located at
high galactic
latitudes (40 ≤ |b| ≤ 90).
Key
words: astrometry
– clusters – luminosity function.
UN MODÈLE
POUR
LE SYSTÈME HD
102928, GÉANTE ROUGE BINAIRE
SPECTROSCOPIQUE,
ÉTOILE DOUBLE
ASTROMÉTRIQUE ET
SYSTÈME TRIPLE
Maurice Imbert1, Jean-Michel
Carquillat2
1 Laboratoire
d’Astrophysique de Marseille, OAMP
2,
place Le Verrier,
F-13248 Marseille, France
E-mail:
Maurice.Imbert@observatoire.cnrs-mrs.fr
2 Laboratoire
d’astrophysique (UMR 5572 du CNRS) de
l’Observatoire Midi-Pyrénées
14,
avenue Edouard Belin, F-31400 Toulouse, France
E-mail:
jean-michel.carquillat@ast.obs-mip.fr
Abstract. We present a new
study of HD 102928 (HR 4544, V = 5.6, K0III), a triple system formed by
a
long-period spectroscopic
binary, which is also an astrometric one detected by
the Hipparcos satellite, and a distant interferometric companion. New,
accurate,
orbital elements for the spectroscopic pair are derived from recent
observations with the Coravel
instrument at Observatoire de
Haute-Provence. They are as follows: P =
490.765 ± 0.094 days; V0 = 14.12 ± 0.06 km/s; e = 0.272 ± 0.006; K = 13.60 ± 0.09 km/s;
w = 126.4° ± 1.3°; T0
= JJ 2451667.7 ± 1.6; a1 sin i = 88.35
± 0.75 Gm; f(m) = 0.114 ± 0.003 MS (solar masses).
From those
parameters, and useful constraints derived from Hipparcos data, we
propose a coherent model for that triple system. In that model
the
spectroscopic pair is constituted by a red giant, the only visible
star, and a
faint (Dmv
= 2.9) G0 dwarf companion; the interferometric
third body can be a cool star of type K5IV. This model is consistent
with
masses of 2.15, 1.05 and 1.15 MS, respectively for
the red
giant primary, the spectroscopic companion and the third body.
Key
words: astrophysics – spectroscopic
binaries – physical parameters.
GP ANDROMEDAE
– A POSSIBLE
DOUBLE-MODE PULSATOR ?
ALEXANDRU POP,
VLAD TURCU, DAN
MOLDOVAN
Astronomical
Institute of the Romanian Academy
Astronomical
Observatory Cluj-Napoca
Str.
Cireşilor
19, 400487 Cluj-Napoca, Romania
E-mail:
[apop, vturcu,
dmoldovan]@academie.cj.edu.ro
Abstract. The aim of this study
on the high-amplitude δ Scuti star GP Andromedae was to find out
whether this
variable is a
double-mode pulsator. The adopted methodology for data processing
(amplitude spectrum analysis, model fitting, significance
estimation for
detected frequencies, different statistical tests) has been applied to
Gieseking et al. (1979) Johnson B and V
photoelectric light
curves. Although an ultimate answer could not be given at this stage,
rigorous
arguments have been supplied
in favour of the double-mode character of GP And
pulsations, the involved secondary frequency being of about 16.2 c/d.
As
a
consequence of such a result, together with the recent estimations of
the
relative period change rate (1/P)(dP/dt), the
evolutionary
stage of this star could be that of post-main-sequence.
Key
words:
variable stars – high-amplitude δ Scuti stars – data analysis.
SIMULTANEOUS
MAGNETIC
FIELD TIME SERIES
IN AR10486
AND AR10488
DURING
THE PERIOD OCTOBER
29–31, 2003
DIANA
BEŞLIU1,2, ALINA-CĂTĂLINA DONEA2, PAUL
CALLY2, GEORGETA MARIŞ1
1 Astronomical
Institute of the Romanian Academy
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
deanna@aira.astro.ro,
gmaris@aira.astro.ro
2 School
of Mathematics and Sciences, Monash University
Victoria
3168,
Australia
E-mail:
alina.donea@sci.monash.edu.au, paul.cally@sci.monash.edu.au
Abstract. We present
simultaneous time series of the line-of-sight magnetic field measured
in two
active regions: NOAA AR10486 and
NOAA AR10488 during the period October 29–31, 2003.
The two regions were very active during this time, producing flares of
type
M
and X. AR10486 produced a large flare of type X10 that induced
significant
seismic activity in the region. We show that rapid variations
of the
line-of-sight magnetic field occurred over a period of minutes during
the flare
explosion. The reversibility of the magnetic field is a very
good tool for
understanding how the magnetic energy is released in large flares and
what
percentage of the total energy could trigger solar
quakes. We have not detected
any association between the line-of-sight magnetic activity of the two
neighbouring active regions. We have
estimated that
only 0.00002% of the total magnetic energy was used by the flare to
ignite the
seismic source of October 29.
Key
words: Sun –
magnetic field – solar flare – autocorrelation.
INTEGRABILITY IN
THE LIGHT OF
THE INVERSE PROBLEM
GEORGE
BOZIS
Department
of Physics, University of Thessaloniki
54006 Thessaloniki, Greece
E-mail:
gbozis@auth.gr
Abstract. For
two-dimensional integrable potentials 
we introduce the
notion of the orbital function 
,
depending on the
two positional variables x, y,
on the energy constant E and on an additional constant 
.
This function satisfies both the (energy-dependent) first
order linear PDE and the (free of energy) second order nonlinear PDE of
the
direct problem of Dynamics. We establish a linear first order PDE
(which
essentially replaces the vanishing Poisson bracket) for the unknown
function 
,
which provides the second integral of motion .
Out of
several possible applications, we treat here in some detail the case of
integrals
of motion quartic in the velocity components 
.
These
integrals are identified by three coefficients to be
determined and this task is reduced to the study of three PDE, each of
which is
solved independently.
Key
words: integrability
– inverse problem –
orbitals – second integrals.
HÉNON-HEILES’
TWO-BODY
PROBLEM. I.
COLLISION AND ESCAPE
DYNAMICS
VASILE
MIOC, DUMITRU PRICOPI
Astronomical
Institute of the Romanian Academy
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mails:
vmioc@aira.astro.ro, dpricopi@aira.astro.ro
Abstract. We tackle the
two-body problem associated to Hénon-Heiles’ famous
potential for two limit situations: collision and escape. For each
such a
situation, we use McGehee-type transformations and construct the
respective
manifold. We fully describe the local flows on these manifolds
and in their
neighbourhood, translating the phase orbits in terms of physical
motion. Many
unusual issues, as: shape of infinity manifold, “allowed”
and “forbidden”
regions for escape, dependence on the energy level, final trends of
collisional
and escape motion, etc., are pointed out.
Key
words:
celestial mechanics – Hénon-Heiles’ model – collision – escape.
the vertical
deviation DETERMINATION
by AN
astronomical geodetic
method
(II): STARS IDENTIFICATION AND
PROCESSING OF
AZIMUTHAL OBSERVATIONS
Octavian BĂdescu1,2, PETRE
POPESCU2, RADU POPESCU2
1 Technical
University of Civil
Engineering
Bd.
Lacul Tei 124, Bucharest, Romania
E-mail:
octavian@aira.astro.ro
2 Astronomical
Institute of the Romanian Academy
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail: petre@aira.astro.ro, pradu@aira.astro.ro
Abstract. In
this paper the method
of stars identification and the algorithms for the processing of the
azimuthal
measurements is presented.
Stars identification is a very important step
because in terrain we know nothing about the observed star.
Identification is
followed by azimuthal
angular observations for a large number of stars,
uniformly distributed on the celestial sphere. Through the introduction
of an
adequate matrix
of weights, the unequal weights of all direct measurements are
taken into account: angular measurements and times at the chronometer.
By
applying the theory of conditional measurements with unknowns, we
obtain a
rigorous algorithm for the determination with maximum efficiency
of all three
fundamental elements of astronomical geodesy: latitude, longitude and
azimuth.
Key
words:
astronomy – geodesy – vertical deviation.
OBSERVATIONS
OF NEPTUNE IN BUCHAREST
DURING
2001–2004: PRECISE
POSITIONS
GHEORGHE
BOCŞA
Astronomical
Institute of the Romanian Academy
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
gbocsa@aira.astro.ro
Abstract. We present the
observations of Neptune obtained during 2001–2004, performed at the Astronomical
Institute
of the Romanian
Academy with the
380/6000 mm astrograph. To compute the normal coordinates
of the object, we used both Turner’s (constants) and
Schlesinger’s
(dependencies) methods.
Key
words:
astrometry – Neptune.