A photometric study of the contact binary AZ Virginis

New light curves and photometric solutions of the contact binary AZ Vir are presented in this paper. The light curves appear to exhibit a typical O'Connell effect, with Maximum I being 0.021 mag (V) and 0.023 mag (B) brighter than Maximum II, respectively. From the observations, six times of minimum light were determined and from the present times of minimum light and those collected from the references, the light elements of the system were improved. The light curves were analyzed by means of the Wilson‐Devinney program. The results suggest that AZ Vir is a W‐subtype contact binary with a mass ratio of q = 0.623(2). The asymmetry of the light curves is explained by star spot models. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

B and V photometry and analysis of the eclipsing binary RZ Cas

Photoelectric light curves of the eclipsing binary RZ Cas are presented forB andV filters. The light curves are analysed for light and geometrical elements, starting with a previously suggested preliminary method. The approximate results thus obtained are then optimised through the Wilson-Devinney computer programs.     

GW Cephei,A W UMa type system

Photoelectric light curves inB andV are presented for GW Cep. The light elements (P=0^d.319) have been refined. Orbital elements have been determined according to the Russell-Merrill method. They show great similarity with those of at least four other well known W UMa systems, e.g. W UMa itself. The similarities of that group are discussed.     

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 andV) 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.     

New photoelectric observations of four W UMa systems: OO aql,V839 Oph,V566 Oph,and SW Lac

The W UMa-type systems (OO Aql, V839 Oph, V566 Oph, and SW Lac) were observed photoelectrically in two wavebands (B andV) during the years 1982–1983. The light curves of these systems are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined. The absolute elements and the period variations of these systems are discussed.     

A photoelectric study of the W UMa-system U Pegasi

The W UMa-system U Pegasi was observed photoelectrically in two wavebands (B andV) in 1984. The light curves of this system are analysed using Kopal's frequency-domain technique and the optimisation method. New geometrical and physical elements have been determined and the period-variations discussed.     

Light curve variations of the eclipsing binary V367 Cygni

The long-period eclipsing binary star V367 Cygni has been observed photoelectrically in two colours,B andV, in 1984, 1985, and 1986. These new light curves of the system have been discussed and compared for the light-variability with the earlier ones presented by Heiser (1962). Using some of the previously published photoelectric light curves and the present ones, several primary minima times have been derived to calculate the light elements. Any attempt to obtain a photometric solution of the binary is so complicated by the peculiar nature of the light curve caused by the presence of the circumstellar matter in the system. Despite this difficulty, however, some approaches are being carried out to solve the light curves which will be discussed shortly.     

Fourier techniques for an analysis of eclipsing binary light curves. V

An integral transform called the momentsA _2m of the light curves has been introduced by Kopal (1975) and utilized in the subsequent papers for an analysis of the light curves of eclipsing variables. The aim of the present paper is to generalize this integral transform by two distinct ways: (i) by introducing an exponential factor, and (ii) a Jacobi polynomial as multiplicative factor into the integrand of the transformA _2m. Observational values of these general transforms are likewise obtainable. They have been expressed in terms of eclipse elementsr _1,2,i andL ₁. These expressions can be used to solve the eclipse elements in terms of observed quantities. Free parameters in the expressions increase the flexibility in applications and may be utilized to improve the determinacy of the elements.     

A photometric study of the eclipsing binary 68 u Her

The aim of this paper is to present and study the light curves (B andV) of the eclipsing binary 68 u Her from the photometric observations made at Al-Battani Observatory.New photometric elements have been obtained by a Fourier analysis of the light changes in the frequency-domain.     

Photometric observations and light curve analysis of ST Aquarii

The system of ST Aquarii has been observed inB andV filters at KOTTAMIA Observatory in Egypt. Two light curves have been obtained and new times of minima have been calculated.The light curves have been analysed using the theory of Fourier transform of light changes in frequencydomain, and new geometrical and physical elements have been obtained.     

Light curves analysis of AB Andromedae

The new B and V light curves of the eclipsing variable AB And obtained during 1979 are analysed. Frequency Domain techniques is used and new geometric and photometric elements are given.     

Fourier techniques for an analysis of eclipsing binary light curves,VII

A Laplace and a Hankel transform of the light curves of eclipsing binary star systems have been expressed in terms of the eclipse elements (L ₁,r _1,2 andi) of the spherical basic model. These general expressions can be used for the solution of the eclipse elements of the systems in terms of the observed quantities.     

Fourier analysis of the light curves of eclipsing variables,XV

A new general expression for the theoretical momentsA _2m of the light curves of eclipsing systems has been presented in the form of infinite series expansion. In this expansion, the terms have been given as the product of two different polynomials which satisfy certain three-term recursion formulae, and the coefficients diminish rapidly with increasing number of terms. Thus, the numerical values of the theoretical momentsA _2m can be generated recursively up to four significant figures for any given set of eclipse elements. This can be utilized to solve the eclipse elements in two ways: (i) with an indirect method (for the procedures see Paper XIV, Kopal and Demircan, 1978), (ii) with a direct method as minimization to the observational momentsA _2m (area fitting). The procedures given in Paper XIV for obtaining the elements of any eclipsing system consisting of spherical stars have been automated by making use of the new expression for the momentsA _2m of the light curves. The theoretical functionsf ₀,f ₂,f ₄,f ₆,g ₂ andg ₄ which are the functions ofa andc ₀, have been used to solve the eclipse elements from the observed photometric data. The closed-form expressions for the functionsf ₂,f ₄ andf ₆ have also been derived (Section 3) in terms of Kopal'sI-integrals.The automated methods for obtaining the eclipse elements from one minimum alone have been tested on the light curves of YZ (21) Cassiopeiae under the spherical model assumptions. The results of these applications will be given in Section 5 which follows a brief introduction to the procedure we followed.     

A photometric study of V566 ophiuchi

The A-type W UMa system V566 Oph was observed photoelectrically in two wavebands (B andV) in the years 1988-1989 at the Kryonerion Astronomical Station of the National Observatory of Athens, Greece. The light curves of the system are analyzed using frequency-domain techniques and new geometric and photometric elements are derived. These elements are combined with the more recent spectroscopic data based on Reticon observations to yield the absolute parameters of the system. The evolutionary status of the system is considered and it is found that V566 Oph has started its evolution away from the Main Sequence. The period of the system continues to increase.     

Fourier techniques for an analysis of eclipsing binary light curves: I

The Fourier techniques developed so far for an analysis of eclipsing binary light curves have been re-discussed. The Fourier coefficients for the analysis have been derived in a simple form of series expansions, in terms of eclipse elements, valid for any type of eclipse (regardless of whetherr ₁r ₂).These coefficients may be utilized to solve the eclipse elements in terms of the observed characteristics of the light curves. A general relation between the observed quantitiesl and , and the eclipse elementsr _1,2,i andL ₁ has also been given in the form of series expansions which can be used for the synthesis of the light curves.     

The solution parameters of very close binary systems

The problems encountered in the derivation of elements from the light curves of very close binary systems are discussed. It is shown that the rectification procedure is critically dependent on the underlying model. The assumption of a contact configuration leads to better coincidence of theoretical and observed light curves. The Fourier analysis method is used to derive the solution parameters of the examples YY Eri and AM Leo. Veröffentlichungen der Dr. Remeis Sternwarte Bamberg, Astronomisches Institut der Universität Erlangen-Nürnberg, volume 10, Nr. 112.     

UBV observation and analysis of VV Orionis

TheUBV photoelectric observation of the eclipsing binary star VV Ori were made at Al-Battani Observatory, Baghdad, Iraq, during nine nights in November and December, 1984 and January, 1985. As a result, three light curves were completed.An analysis of theB andV normal points light curves using the optimization method shows the existence of a slight shift in the primary mid-minimum epoch and the temperature of the secondary component is consistent with B5-type star. A new set of geometrical and physical elements is also presented.     

Photometry and analysis of the eclipsing variable GO Cygni

Photoelectric observations of the eclipsing binary GO Cyg have been carried out inB andV colours at the Ege University Observatory. The corresponding light curves were analyzed by the method of Wilson-Devinney. The system was found to be a reverse Algol semi-detached binary. The absolute elements of the system are also deduced.     

UV Leo: The Binary with the Two Suns

BV light curves of the eclipsing binary UV Leo obtained at the Kryonerion Astronomical Station of the National Observatory of Athens, Greece, are analyzed. The analysis is based on a Roche configuration with two spots on the secondary surface. The elements of the two components of the system are calculated and the spot characteristics are given.     

Photo-electric study of the eclipsing binary RU Eridani

B andV observations of the eclipsing binary RU Eridani made on 23 nights during 1974–76 are reported. An improved period of 0^d.63219951 is derived. After rectification ofB andV light curves, new elements are derived using Russel-Merrill method. The system is classified as semidetached.