Pressure Calculation of
a Constant-Density Star in
the Dynamic Theory
of Gravity
Ioannis Iraklis Haranas
Department of Physics and Astronomy
E-mail: ioannis@yorku.ca
Abstract. In a new theory
called Dynamic Theory of Gravity, the
gravitational potential is derived from gauge relations and has a
different
form
than the classical Newtonian potential. In the same theory an
analytical
expression for the pressure is derived from the equation of the
hydrodynamic
equilibrium, which is solved for a star of constant density and the
results are
compared with those of Newtonian gravity. Changes in the central
pressure and
radius are calculated, too, and finally a redshift calculation is
performed, so
that the dynamic gravity effects, if any, might be shown
to be of some
detectable magnitude.
Key words: dynamic theory of gravity – gauge fields – Weyl’s quantum principle.
VIRIALIZED HICKSON COMPACT GROUPS OF GALAXIES
IBRAHIM MOHAMED SELIM1, INALL ADHAM HASSAN2,
HAMED ABD-ALHAMED ISMAIL1, MAGDY MAHROS ALKATEEB1
1 National
Research Institute of
Astronomy and Geophysics, Helwan,
E-mail:
i_selim@yahoo.com
2 Astronomy
Department, Faculty of
Sciences,
Abstract. We
investigate the dynamical stability of Hickson compact groups of
galaxies
through the virial theorem. The mass-luminosity
ratio values of galaxies can be
used to obtain the luminous mass in compact groups of galaxies. The
average
luminous mass of a member
of the group is approximately 1.3´1011 MΘ, whereas the average total luminous mass of
the group is approximately 4.6´1011 MΘ. The
virial theorem has been used to estimate
the virial mass. The average virial mass of the group of galaxies is
approximately 6.3´1013
MΘ,
This is attributed to the presence of a
large amount of dark matter: more than 90% in this group. The virial to
luminous masses ratio is due
to the instability of groups. We conclude that the
Hickson compact groups of galaxies are unstable.
Key words: galaxies – groups of galaxies – luminosity – masses.
THE
ECLIPSING BINARY
AW
UMA: OBSERVATIONS AT
PETER ROVITHIS1, ALEXANDRU DUMITRESCU2, HELEN ROVITHIS-LIVANIOU3, GABRIELA OPRESCU2, MARIAN DORU ŞURAN2
1 Institute of Astronomy and Astrophysics
National
Observatory of
E-mail:
rovithis@astro.noa.gr
2 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
alex@aira.astro.ro,
suran@aira.astro.ro
3 Section of Astrophysics-Astronomy and Mechanics
Department.
of Physics,
Panepistimiopolis,
Zografos 157 84,
E-mail:
elivan@ cc.uoa.gr
Abstract. BV and UBV
photoelectric observations of the contact binary AW UMa
– carried out at the Kryonerion Astronomical Station of the
National
Observatory of Athens, Greece, and at the Bucharest Observatory,
light are given, too,
and some of the corresponding light curves are presented. A general
discussion
concerning this very interesting eclipsing binary
is made.
Key words: eclipsing binaries – light curves – AW UMa.
STUDY
OF THE ORBITAL
PERIOD VARIATION OF
THE
NABIL Shoukry
AWADALLA, MONIR
AHMED
HAMDY,
MAGDY ABDEL-MALEK HANNA, ABDEL-FADY BESHARA MORCOS
National
Research Institute of Astronomy and
Geophysics, Helwan,
E-mail:
magdyamh@yahoo.com
Abstract.
The (O–C) diagram of BV Draconis has
been analyzed. The depth
variability of the light curves’ minima for the system has been
studied.
The
depth variation may be explained as magnetic cycles effect. A relation
between
the magnetic cycling and the period variation has been proposed.
Key words: astrophysics – eclipsing binaries – period variation – magnetic activity.
HÉNON-HEILES’ TWO-BODY PROBLEM. II. MAIN FEATURES OF THE GLOBAL FLOW
DUMITRU PRICOPI, VASILE MIOC
Astronomical
Institute of the
Str.
Cuţitul de Argint 5, 040557
E-mail: dpricopi@aira.astro.ro, vmioc@aira.astro.ro
Abstract. We tackle the
two-body problem associated to Hénon-Heiles’ famous
potential. We fully describe the flows on the radial orbits and in
their
neighbourhood, and point out the main features of the global flow.
Key words: celestial mechanics – Hénon-Heiles’ model – global flow
NOTE ON THE PHOTOGRAVITATIONAL RESTRICTED THREE-BODY PROBLEM
CIPRIAN CHIRUŢĂ 1, TIBERIU OPROIU 2
1 “Ion
Ionescu de la Brad”
Aleea
M.
Sadoveanu 3, 700490 Iaşi, Romania
E-mail:
kyru@univagro-iasi.ro
2 Astronomical
Institute of the
Astronomical
Observatory Cluj-Napoca
Str. Cireşilor 19,
400487 Cluj-Napoca, Romania
E-mail:
toproiu@email.ro
Abstract. We
present the
photogravitational restricted three-body problem for the radiation
pressure
model proposed by Constantin Popovici in 1923.
We establish the differential
equations of the relative motion of the body with a negligible mass.
Key words: restricted three-body problem – radiation pressure – orbital energy.
OBSERVING
NEAR EARTH ASTEROIDS
WITH
A SMALL TELESCOPE.
II.
THE PROGRAM AT
OVIDIU VĂDUVESCU 1,2
1
128
Petrie Science Building,
Email: ovidiuv@yorku.ca
2 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
Email:
ovidiuv@yahoo.com
Abstract. Five Near Earth Asteroids have been observed
during ten nights at York University Observatory, part of a NEA
follow-up
program initiated by the author in 2002. The astrometric and
photometric data
were sent to the Minor Planet Centre, following which
an observatory code was
assigned and four batches have been included in the NEODyS database and
MPC
Circulars. In the first paper
we discussed the planning of the NEA observations.
In this paper we present the program at
The results are applicable to any other small
facility.
Key words: astrometry – NEAs – PHAs – CCD observations.
ASTRONOMICAL
REFRACTION CALCULATION FOR
THE EARTH’S ELLIPSOIDAL
ATMOSPHERE
AT
GREAT ZENITH DISTANCES
MINODORA LIPCANU
Str.
Academiei 14, 010014
E-mail:
mlipcanu@xnet.ro
Abstract. We calculate the
astronomical refraction for the Earth’s
ellipsoidal atmosphere, when the light ray situated in the meridian
plane of
the place is observed at a zenith distance between 70° and 81° .The calculation is made using the
model of the terrestrial atmosphere TSA-60.
It represents an extension of the
calculation of the astronomical refraction for the ellipsoidal
atmosphere at
zenithal distances smaller than 70°.
By
comparing these results to the ones of the spherical model, it is
ascertained
that in this case also the refraction calculated for the ellipsoidal
model is
greater than the one for the spherical model, the difference increasing
with
the zenith distance and depending on the latitude of the place.
Key words: astrometry – astronomical refraction – atmospheric models.