THE  INTERNATIONAL  HELIOPHYSICAL  YEAR

Joseph  M.  Davila,  Nat  Gopalswamy,  Barbara  J.  Thompson

NASA Goddard Space Flight Center

Greenbelt, MD 20771, USA

E-mails: davila@stars.gsfc.nasa.gov, gopals(@)fugee.gsfc.nasa.gov, barbara.j.thompson@nasa.gov

Abstract. On October 4, 1957, only 53 years after the beginning of flight, the launch of Sputnik 1 marked the
beginning of the space age; as mankind took the first steps to leaving the protected environment of Earth’s atmosphere.
Discovery of the radiation belts, the solar wind, and the nature of Earth’s magnetosphere prepared the way for the
inevitable human exploration to follow. Soon, Cosmonauts and Astronauts orbited Earth, and then in 1969, Astronauts
landed on the Moon. Today a similar story is unfolding, the spacecraft Voyager has crossed the termination shock, and
will soon leave the heliosphere. For the first time, man will begin to explore the local interstellar medium. It is inevitable
that, during the next 50 years, exploration of the solar system including the Moon, Mars and the outer planets will be the
focus of the space program, and, like 50 years ago, unmanned probes will lead the way, followed by human exploration.

Key words: solar physics – heliosphere – International Heliophysical Year.

 

 

 

GALAXY  PAIRS  AND  STAR  FORMATION  ACTIVITY  IN  HICKSON  COMPACT  GROUPS

IBRAHIM  SELIM,  GAMAL  BAKR  ALI,  HAMED  ISMAIL,  AHMED  ESSAM,

ALI  HAROON,  MOHAMED  ABDEL-SABOUR

National Research Institute of Astronomy and Geophysics (NRIAG)

11421-Helwan, Cairo, Egypt

E-mail: selim@nriag.sci.eg

Abstract. We investigate the effect of galaxy interaction on star formation in dense environment through the far-infrared
emission (FIR) of galaxies using data of Hickson Compact Groups (HCGs). We identified 470 galaxy pairs with cr
(proximity criterion) ≤ 390, and 358 galaxy pairs with rp (projected separation) less than 100 kpc and difference in velocity
DV ≤ 350 km/s. We identified 41 close galaxy pairs with rp less than 25 kpc and DV ≤ 100 km/s. The star formation rate
(SFR) of galaxies in galaxy pairs is found to be enhanced for close galaxy pairs. The large fraction of star formation activity is
probably due to the activity in the exchange of matter between the companions. We established the catalogue of galaxy pairs
in HCGs.

Key words: extragalactic astronomy – galaxy pairs – Hickson compact groups.

 

 

 

ON  THE  DETECTION  AND  DIAGNOSIS  OF  LOW-LEVEL  STELLAR  VARIABILITY

ALEXANDRU  POP

Astronomical Institute of the Romanian Academy

Astronomical Observatory Cluj-Napoca

Str. Cireşilor 19, 400487 Cluj-Napoca, Romania

E-mail: apop@academie.cj.edu.ro

Abstract. The problem of detection and diagnosis of stellar variability phenomena is approached via the method proposed
by Pop (2005) and derived from that of Kuschnig et al. (1997). The numerical experiments performed by us prove its ability
to detect low-amplitude periodic signals in the presence of Gaussian and AR1 noise as well as the presence of the high-noise
level.

Key words: astrophysics − stellar variability – data analysis.

 

 

 

ON  THE  LIGHT-CURVE  SHAPE  OF  DL  CAS

ALEXANDRU  POP

Astronomical Institute of the Romanian Academy

Astronomical Observatory Cluj-Napoca

Str. Cireşilor 19, RO-400487 Cluj-Napoca, Romania

E-mail: apop@academie.cj.edu.ro

Abstract. The study of the temporal behavior of DL Cassiopeiae light curve shape is resumed. The present approach is based
on the use of the previously introduced structural parameters (Pop and Roman 2006) through the relative length of given light
curve branches, or relative surface areas delimited by the light curve and well-defined magnitude levels. The variability survey
was performed using two methods based on numerical simulations. In spite of the overall conclusion concerning the light curve
stability, the hypothesis of the presence of some low level, time-dependent, distortions of the light curve profile, both in minimum
and maximum light, may be taken into account. Unfortunately, at this moment the pathological effects of poor phase coverage and
of the too long time-base of some existing data sets cannot be surpassed. That is why, new high-quality photometric observations,
with good phase coverage, are needed in order to understand the temporal behavior of DL Cas light curve.

Key words: variable stars – δ Cephei stars – light-curve shape variability.

 

 

 

THE  LENNARD-JONES-TYPE  TWO-BODY  PROBLEM.  I.  COLLISION  AND  ESCAPE  DYNAMICS

VASILE  MIOC

Astronomical Institute of the Romanian Academy

Str. Cuţitul de Argint 5, 040557 Bucharest, Romania

E-mail: vmioc@aira.astro.ro

Abstract. We extend the famous Lennard-Jones potential (characteristic to molecular dynamics) to the astronomical framework.
We tackle the two-body problem only via qualitative, geometrical methods of the theory of dynamical systems. Here we approach
two limit situations: collision and escape, describing the dynamics in their neighbourhood. This is only the first step in understanding
this problem from a qualitative standpoint.

Key words: celestial mechanics ­ two-body problem − Lennard-Jones potential − collision − escape.

 

 

 

VENUS’  TRANSIT  2004:  OBSERVATIONS  AND  ANALYSIS  OF  THE  BLACK-DROP  EFFECT

ADRIAN  SABIN  POPESCU 1,  MIRCEA  RUSU 2

1 Astronomical Institute of the Romanian Academy

Str. Cuţitul de Argint 5, 040557 Bucharest, Romania

E-mail: sabinp@aira.astro.ro

 

2 University of Bucharest, Faculty of Physics

Str. Atomiştilor 1, CP MG-11, 077125 Bucharest-Măgurele, Romania

E-mail: mvrusu@yahoo.com

Abstract. The transit of Venus across the solar disk took place on June 8, 2004. Using a fractal method of image processing on
TRACE satellite images, we determine the moment (before the third contact) at which the black-drop effect occurred.

Key words: Venus’ transit − black-drop effect − image analysis − fractal dimension.