SS Ari: a shallow-contact close binary system

Two CCD epochs of light minimum and a complete R light curve of SS Ari are presented. The light curve obtained in 2007 was analyzed with the 2003 version of the W-D code. It is shown that SS Ari is a shallow contact binary system with a mass ratio $q=3.25$ and a degree of contact factor f=9.4(\pm0.8%). A period investigation based on all available data shows that there may exist two distinct solutions about the assumed third body. One, assuming eccentric orbit of the third body and constant orbital period of the eclipsing pair results in a massive third body with $M_3=1.73M_{\odot}$ and P_3=87.0$yr. On the contrary, assuming continuous period changes of the eclipsing pair the orbital period of tertiary is 37.75yr and its mass is about$0.278M_{\odot}$. Both of the cases suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table

New photoelectric observations and elements of the eclipsing W UMa-type system V839 Oph

The W UMa-type system V839 Oph was observed photoelectrically in two wavebands (B and V) during 1985 at the Kryonerion Astronomical Station of the National Observatory of Greece. The light curves of the system are analysed using the frequency-domain techniques and new geometric and photometric elements are given. The light variations of the system are also discussed. © 1989 Kluwer Academic Publishers

On the gaia expected harvest on eclipsing binaries

The space experiment Gaia, the approved cornerstone 6 ESA mission, will observe up to a billion stars in our Galaxy and obtain their astrometric positions on a micro-arcsec level, multi-band photometry as well as spectroscopic observations. It is expected that about one million Eclipsing Binaries (EBs) (with V ≤ 16 mag) will be discovered and the observing fashion will be quite similar to Hipparcos/Tycho mission operational mode. The combined astrometric, photometric and spectroscopic data will be used to compute the physical parameters of the observed EBs. From a study of a small sample of EBs, it is shown that the agreement between the fundamental stellar parameters, derived from ground-based and Hipparcos (Gaia-like) observations, is more than satisfactory and the Gaia data will be suitable to obtain accurate binary solutions. © Springer Science+Business Media B.V. 2006

On the evaluation of the photometric proximity effects of close eclipsing systems

The aim of the present paper has been to generalize the method, developed by Kopal (1976), for the evaluation of the photometric proximity effects (between minima as well as within eclipses) of distorted eclipsing systems. The method is extended to quantities of second order (n-7) is surficial distortion. Analytical expressions of the polynomials to be used for 'modulation' of the light curve are also given. © 1981 D. Reidel Publishing Co

On the evaluation of the photometric proximity effects of close eclipsing systems

The aim of the present paper has been to generalize the method, developed by Kopal (1976), for the evaluation of the photometric proximity effects (between minima as well as within eclipses) of distorted eclipsing systems. The method is extended to quantities of second order (n-7) is surficial distortion. Analytical expressions of the polynomials to be used for 'modulation' of the light curve are also given. © 1981 D. Reidel Publishing Co

New photoelectric observations and elements of the eclipsing W UMa-type system V839 Oph

The W UMa-type system V839 Oph was observed photoelectrically in two wavebands (B and V) during 1985 at the Kryonerion Astronomical Station of the National Observatory of Greece. The light curves of the system are analysed using the frequency-domain techniques and new geometric and photometric elements are given. The light variations of the system are also discussed. © 1989 Kluwer Academic Publishers

Contact binaries: A study of the proximity effects and gravity darkening based on kopal's fourier method

A new method for the determination of the proximity effects and gravity darkening exponents in contact binaries of W UMa type is presented. The method is based on Kopal's method of Fourier analysis of the light changes of eclipsing variables in the Frequency Domain. The method was applied to 36 W UMa systems for which geometric and photometric elements have been derived by the most powerful techniques. The derived values are very close to those predicted by the existing theory of radiative transfer or convective equilibrium. © Springer 2005

Ground-based and space observations of interacting binaries

Multi-wavelength observational data, obtained from ground-based and space observations are used to compute the physical parameters of the observed Interacting Binaries (IBs) and study the interactions and physical processes in these systems. In addition, the database of IBs from ground-based surveys and space missions will provide light curves for many thousands of new binary systems for which extensive follow up ground-based observations can be carried out. In certain cases, light curves of superior quality will allow studies of fine effects of stellar activity and very accurate determination of stellar parameters. Moreover, many new discoveries of interesting systems are expected from ground-based all-sky surveys and space missions, including low mass binaries and star-planet binary systems. The most important current and future programs of observations of IBs from ground and space are presented. © International Astronomical Union 2012

UBV photometric study of the eclipsing binary DM Delphini

The near-contact system DM Del with an A2V primary and a G8 secondary was observed in U, B and V wavelengths in July 1998. A new seasonal light curve is presented and a new observed time of minimum is given. The unperturbed part of the light curve was used to determine some basic parameters of the system with the Wilson-Devinney code, some of which were kept fixed for spot modelling of the light curves. A simple spot distribution was determined, based on a model with two cool spots on the surface of the secondary. Absolute elements were calculated and the evolutionary status was determined

Masses and angular momenta of contact binary stars

Results are presented on component masses and system angular momenta for over 100 low-temperature contact binaries. It is found that the secondary components in close binary systems are very similar in mass. Our observational evidence strongly supports the argument that the evolutionary process goes from near-contact binaries to A-type contact binaries, without any need of mass loss from the system. Furthermore, the evolutionary direction of A-type into W-type systems with a simultaneous mass and angular momentum loss is also discussed. The opposite direction of evolution seems to be unlikely, since it requires an increase of the total mass and the angular momentum of the system. © 2006 The Authors. Journal compilation © 2006 RAS