A5091636477- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- History and Developments in Astronomy
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Historical Astronomy and Related Studies
- Surface Roughness and Optical Measurements
- Atomic and Molecular Physics
- Pulsars and Gravitational Waves Research
- Atmospheric Ozone and Climate
- Optical Systems and Laser Technology
- Infrared Target Detection Methodologies
- Astrophysics and Cosmic Phenomena
- Tribology and Lubrication Engineering
- Optical Polarization and Ellipsometry
- Advanced Measurement and Detection Methods
- Atmospheric and Environmental Gas Dynamics
- Particle Accelerators and Free-Electron Lasers
National and Kapodistrian University of Athens
2007-2021
Hella (Germany)
2016
European Space Research and Technology Centre
2007
University of California, Irvine
2003
University of Maryland, College Park
2003
Union astronomique internationale
2003
Nanjing University
2003
Tartu Observatory
2001
University of Manchester
1976-1978
The catalogue contains 199 confirmed cases of binary systems containing at least one pulsating component δ Sct type.The sample is divided into subgroups in order to describe the properties and characteristics type stars binaries according their Roche geometry.Demographics describing quantitatively our knowledge for these as well distributions components Mass-Radius, Colour-Magnitude Evolutionary Status-Temperature diagrams are presented discussed.It shown that a threshold ∼13 days orbital...
(Abridged) OJ287 is a BL Lac object that has shown double-peaked bursts at regular intervals of ~12 yr during the last ~40 yr. We analyse optical photopolarimetric monitoring data from 2005-2009, which latest outburst occurred. The aim this study twofold: firstly, we to variability patterns and statistical properties polarization light-curve. find strong preferred position angle in polarization. can be explained by separating jet emission into two components: an core chaotic emission. stable...
CCD observations of 68 eclipsing binary systems, candidates for containing δ Scuti components, were obtained. Their light curves are analysed using the period04 software possible pulsational behaviour. For systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ AU Lac, CL Lyn and IO UMa, complete observed due to detection a pulsating component. All them, except Aql with modern astronomical softwares in order determine their geometrical characteristics. Spectroscopic Cet Cyg used estimate...
Binary and multiple stellar systems are numerous in our solar neighborhood with 80 per cent of the solar-type stars being members high order multiplicity. The Contact Binaries Towards Merging (CoBiToM) Project is a programme that focuses on contact binaries systems, as key for understanding nature. goal to investigate coalescence merging processes, final state evolution low-mass binary systems. Obtaining observational data approximately 100 eclipsing more than 400 archival aspires give...
The blazar OJ 287 has produced two major optical outburst events during the years 2005–2008. These are latest in a series of outbursts that have occurred repeatedly at 12 year intervals since early 1900s. It been possible to explain historical light curve fairly well by using binary black hole model where secondary impacts accretion disk primary twice orbital cycle. We will ask here how does light-curve fit with this model. use 10 million particle hole. rate transfer particles through...
Results are presented on component masses and system angular momenta for over a hundred low-temperature contact binaries. It is found that the secondary components in close binary systems very similar mass. Our observational evidence strongly supports argument evolutionary process goes from near-contact binaries to A-type binaries, without any need of mass loss system. Furthermore, direction into W-type with simultaneous momentum also discussed. The opposite evolution seems be unlikely,...
The double-mode pulsation of GSC 00144-03031 has been detected when searching for COROT targets. A very large dataset composed 4722 photometric measurements was collected at six observatories in Europe and America. There is no hint the excitation additional modes (down to 0.6 mmag) therefore seems be a pure pulsator, with short fundamental radial mode (P = 84 min). From uvbyβ photometry evolutionary tracks it appears Pop. I star M 1.75 , located middle instability strip, close Zero-Age Main...
CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted improvements physics stellar structure and evolution models massive stars. Further asteroseismic constraints can be obtained from studying ensembles a young open cluster, which all have similar age, distance chemical composition. AIMS: To improve our comprehension stars, we studied cluster NGC 884 to discover new B-type pulsators, besides two known other variable METHODS: An extensive multi-site...
The paper presents combined spectroscopic and photometric orbital solutions for four close binary systems: SW Lyn, QW Gem, AP Leo V2150 Cyg. data are new, while the spectroscopy has been recently obtained within radial velocity programme at David Dunlap Observatory. This is first in planned series of investigations. We give an extensive description motivation main assumptions made our solutions. targets this investigation span a range typical configurations thus present different levels difficulty
New high-quality CCD photometric light curves for the W UMa-type systems V410 Aur, CK Boo, FP V921 Her, ET Leo, XZ V839 Oph, V2357 AQ Psc and VY Sex are presented. The new multicolor curves, combined with spectroscopic data recently obtained at David Dunlap Observatory, analyzed Wilson-Devinney code to yield physical parameters (masses, radii luminosities) of components. Our models all ten resulted in a contact configuration. Four binaries (V921 Oph Sex) have low, while two (V410 Aur Boo)...
ABSTRACT Ultra-short orbital period contact binaries (Porb < 0.26 d) host some of the smallest and least massive stars. These systems are faint rare, it is believed that they have reached a configuration after several Gyrs evolution via angular momentum loss, mass transfer, loss through stellar wind processes. This study conducted in frame Contact Binaries Towards Merging (CoBiToM) Project presents results from light curve analysis 30 ultra-short binaries, with aim to investigate...
Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether eclipsing body system is indeed a dark disk understand observed changes depth durations eclipses. Multicolour photometric data spectroscopic observations at both low high resolution collected. We numerically modelled variations brightness colour tested models with different structure. considered possibility precession. The complete set collected last three are made available...
We present the results of multisite observations δ Scuti star V 1162 Ori.The were done in period October 1999 -May 2000, when 18 telescopes at 15 observatories used to collect 253 light extrema during a total 290 hours time-series observations.The purpose was investigate amplitude and variability previously observed this star, search for low-amplitude frequencies.We detect, apart from main frequency its two first harmonics, four additional frequencies curves, all with low amplitudes (1-3...
A photometric analysis of the W UMa systems V 700 Cyg and AW Vir, based on photoelectric B light curves, is presented. Since no spectroscopic mass-ratio available, q-search method was applied to find preliminary range in order search for final solution. First, an unspotted solution carried out by using unperturbed parts curves applying DC program WD code. The spotted made adopting spot models two systems. In case Cyg, cool spots were placed primary (more massive, larger cooler) component...
We report that the intermediate amplitude δ Scuti star V 1162 Ori has changed its main pulsational period in course of year 2000. This new change falls a sequence changes observed during last 5 years. While average value all our data, 63 mmag, fits cyclic variation suggested by Arentoft et al. (2001), splitting data up smaller subsets discloses significant deviations from regularity, with stretches constant short intervals time. The show one secondary frequencies, f2, 3 years dropped more...
New CCD observations of the contact binary system BH Cas are presented in this paper. times minima and an ephemeris based on our also given. Complete light curves obtained V, R I filters have been analyzed with Wilson-Devinney code to derive geometrical physical parameters system. The final solution leads a configuration (). We found that photometric mass ratio differs from spectroscopic one by about 13% , discrepancy which is not uncommon for other W UMa systems. absolute elements used...