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.     

1992 UBV observations of UV piscium and light curve analysis

In 1992 UBV photometry of short period binary system UV PSc were presented. The results obtained from the analysis ofU, B andV light curves represent transit solutions. The light fluctuations of out-side eclipses have been interpreted in terms of cool star-spots on the photosphere of the primary component. Its parameters have been determined.     

New photoelectric observations of VW Cephei

The aim of the present paper is to present the newB andV light curves of the eclipsing binary VW Cep, obtained with the 48-in. reflector of the National Observatory of Athens, Greece.In the introduction general information for the system is given. In Section 2 some observational and reductional details are given and the obtained light curves are represented. Section 3 deals with the period of the system which was found to continue its shortening. Finally, in Section 4, a general discussion concerning our light curves is given.     

New analysis of II Peg 1977 light curve

The solution of the inverse photometric problem for spotted stars obtained on the basis of the analytical solution of the direct problem is applied to II Peg 1977 light curve. The geometric parameters of the spot configuration so obtained are unambigously determined in contrast to the cases when analysis of the light curve is done on the basis of numerical modelling. A comparison between both methods has been carried out.     

New BV photoelectric observations of BX Andromedae

Photoelectric observations of BX Andromedae made with the 48 inch Cassegrain reflector at the Kryonerion Astronomical Station of the National Observatory of Athens during 1981 and 1982 are presented.     

Ubvr light curves of 44i Bootis during 1978

In this paper theU, B, V, R light curves of the eclipsing variable 44i Boo, obtained during 1978, are represented and discussed.     

BVRI photometric observations,light curve solutions and orbital period analysis of BF Pav

A new ephemeris,period change analysis and light curve modeling of the W UMa-type eclipsing binary BF Pav are presented in this study.Light curves of the system taken in BVRI filters from two observatories,in Australia and Argentina,were modeled using the Wilson-Devinney code.The results of this analysis demonstrate that BF Pav is a contact binary system with a photometric mass ratio q=1.460 ± 0.014,a fillout factor f=12.5%,an inclination of 87.97 ± 0.45 deg and a cold spot on the secondary component.By applying the distance modulus formula,the distance of BF Pav was calculated to be d=268 ± 18 pc which is in good agreement with the Gaia EDR3 distance.We obtain an orbital period increase at a rate of 0.142 s century-1 due to a quadratic trend in the O-C diagram.Also,an alternative sudden period jump probably occurred which could be interpreted as a rapid mass transfer from the lower mass star to its companion of about ΔM=2.45 × 10~(-6) M_⊙.Furthermore,there is an oscillatory behavior with a period of 18.3±0.3 yr.Since BF Pav does not seem to have significant magnetic activity,this behavior could be interpreted as the light-time effect caused by an undetected third body in this system.In this case,the probability for the third body to be a low mass star with M≥ 0.075 M_⊙or a brown dwarf is 5.4% and 94.6% respectively.If we assume i'=90°,a_3=8.04±0.33 AU.The mass of the secondary component was also determined following two different methods which result close to each other.     

New light curve analysis and period changes of the overcontact binary EQ Tauri

A photometric CCD study of EQ Tauris was carried out in the R, V and B bands. These new data were analyzed by using the PHOEBE and Binary Marker 3 programs, which yielded the geometrical system parameters and mass and radius of both stars. We find these to confirm the results of Pribulla and Vanko (2002). Using these new data together with data from the literature, the orbital period variations were studied by using the Kalimeris method. We find the same timescale of variability of the orbital period as Pribulla and Vanko (2002), namely about 49 years.     

The peculiar eclipsing star BD+13°3496 (V508 ophiuchi): New BV observations and light curve analysis

New BV photoelectric observations of the W UMa-type system V508 Ophiuchi, made in 1986 at the Kryonerion Astronomical Center of the National Observatory of Athens, Greece, are given. The corresponding mean light curves, as well as those obtained in 1981 at the same station using the same instruments, are analysed using frequency-domain techniques. The geometrical and photometric elements of the system have been found. These are combined with the now available spectroscopic data of the system to get its absolute elements. A general discussion for the light variations between the old and the new observations is made. From the light curve analysis it was found that V508 Oph is an A-type W UMa binary with both of its components to fill their corresponding Roche lobes.     

New techniques of light curve analysis: Application to V444 Cygni

A new method of light curve analysis is introduced for systems containing one component possessing an extended atmosphere. Occultation or partial eclipses may be treated with or without the presence of transparency effects. Besides admitting an arbitrary degree of transparency to the eclipsing component, an arbitrary law of limb-darkening may also be assigned to the eclipsed star. The method is applied to the analysis of continuum, narrow band light curves of V444 Cygni obtained by Cherepashchuk and Khaliullin. Primary and secondary minima are examined separately with reasonable results.     

The light curve analysis of MM Herculis

The photoelectric light curves of MM Her obtained in 1983 and 1984 by Evren (1985, 1987) were analyzed by two different methods. Firsly, the effects of the wave-like distortions on the observations were removed from the observed magnitudes by obtaining its mathematical expression. The remaining light curves were analyzed by using Wood's approach. Later, the light curves of the same years were treated by the method of Wilson-Devinney and distortions seen in the light curves were thought to be explained by locating the spots on the surface of the cooler component. The results obtained by two different approaches are in good agreement.     

Analysis of the photoelectric light curve and the orbital period variations of the binary system UU Andromedae

In this work, the analysis of the photoelectric light curve (LC) in the broad‐band filter (400–700 nm) for the UU And system was carried out using the PHOEBE program (vers. 0.31a). The absolute dimensions of the system are determined and its evolution is discussed. Moreover, the period changes of the system are studied using updated O – C data, which shows a cyclic change with a period of P_mod = 18 yr. This was attributed to a magnetic activity cycle operating in this system. In addition to the cyclic change, a long‐term secular variation due to mass transfer from the secondary to the primary component with a rate of 6.17×10^–9 M_⊙ yr^–1 was also detected. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

BVRI photometry and light curve analysis of VW CEP

Synthetic light curve solutions for the W UMa-system VW Cep have been determined by applying the most new version of Wilson (1998)approach to B-observations of 1996 and VRI-observations of 1999. From a consideration of the possible evolution of this system, it is found that the system is a partial eclipsing contact one, and its primary to be a nearly Main-Sequence F5 star of mass 0.85 M _⊙ and the secondary to be a dwarf of spectral type G0 of mass 0.34 M _⊙. This revised version was published online in July 2006 with corrections to the Cover Date.     

New developments in eclipsing binary light curve modeling

The light curve modeling of binary stars has continued to evolve since its founding by Henry Norris Russell (see Russell and Merrill 1952 and citations therein) nearly a century ago, accelerated in the 1950s by Kopal's introduction of Roche geometry into models and by the development of synthetic light curve computer code in the 1970's. Improved physics and the use of more kinds of observational input are providing another round of important advances that promise to enlarge our knowledge of both binary stars and ensembles containing them. Here we discuss the newer horizons of light curve modeling and the steps being taken toward them.     

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.     

Radar and photoelectric observations of asteroid 2100 Ra-Shalom

Results of 13-cm-wavelength radar observations and V-filter photoelectric observations of Ra- Shalom during its 1981 Aug–Sep apparition are reported. The radar data yid detections of echoes in the same sense of circular polarization as transmitted (i.e., the SC sense) as well as in the opposite (OC) sense. The estimate of the ratio of SC to OC echo power, μ_c = 0.14 ± 0.02, indicates that most, but certainly not all, of the backscattering is due to single reflections from surface elements that are fairly smooth at decimeter scales. The value obtained for the OC radar cross section on Aug 26 (1.2 ± 0.3 km²) is about three times larger than those obtained on Aug 23, 24, and 25. The echo bandwidth appears to be within about 1.5 Hz of 5.0 Hz on each date. The photoelectric data suggest a value, P_syn = 19.79 hr, for the synodic rotation period, and yield a composite lightcurve with two pairs of extrema. Combining this value for P_syn with a firm lower bound (4 Hz) on the maximum echo bandwidth yields a lower bound of 1.4 km on the maximum distance between Ra-Shalom's spin axis and any point on its surface.     

Light curve analysis of contact binaries: Characteristic quantities of the light curve

Quantities characterizing light curves of contact binaries of W UMa-type are introduced. For 2700 cases, theoretical light curves of contact binaries are computed by the light curve synthesis method, and characteristic quantities for these light curves are tabulated. An example of application of the table to the light curve analysis of contact binaries is shown, and the errors inherent in the solution are also discussed.     

Photometric observation and light curve analysis of binary system ER-Orionis

Photometric observations of the over-contact binary ER ORI were performed during November 2007 and February to April 2008 with the 51 cm telescope of Biruni Observatory of Shiraz University in U, B and V filters (Johnson system) and an RCA 4509 photomultiplier. We used these data to obtain the light curves and calculate the newtimes of minimum light in each filter and plot the O-C diagram of ER ORI. Using theWilson’s computer code with the help of an auxiliary computer program to improve the optimizations, the light curve analyses were carried out to find out the photometric elements of the system.