Photometric study of the light curve of the neglected eclipsing binary FU Ara

The unique (1954–1956) photoelectric B and V light curves of the EB‐type eclipsing variable FU Ara are here analyzed. The Wilson‐Devinney Differential Correction program was used and the analysis of the results shows that the best fit was obtained at photometric mass ratio q = 0.399 and inclination i = 83°, the primary minimum shows a transit. The star is a semi‐detached system with the secondary that accurately fills its limiting lobe. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Light curve solutions for eclipsing binaries in NGC 188

We present light curve solutions for the W UMa-type eclipsing binaries EP, EQ, ER, ES, and V369 Cep in the old open cluster NGC 188. Using light curve solution parameters combined with reasonable mass estimates, we determine the distance modulusV-M _vof the cluster. Our aim is to examine if current uncertainties in the cluster's distance and age can be resolved. Three binaries yield distance moduli close to 10 _. ^m 80 (±0 _. ^m 08), two others give values around 11 _. ^m 40(±0 _. ^m 09). Depending on the amount of reddening, we find a weighted mean distance modulus for all five binaries between 11 _. ^m 01 and 11 _. ^m 05 (±0 _. ^m 06), which lends modest support for the lower distance (1.65 kpc) and older age (10 Gyr) of the cluster.Participants in the Research Experience for Undergraduates (REU) program at Florida International University, sponsored by the National Science Foundation.     

Radial velocity and light curves analysis of the eclipsing binary NN Vir

The eclipsing binary NN Vir is a short period system showing an EW‐type light curve. Photometric observations of NN Vir were done by Gomez‐Ferrellad & Garcia‐Melendo (1997) at Esteve Duran Observatory. We used photometric data of NN Vir for light curve analysis. The available spectroscopic data of NN Vir is new and we also used the first radial velocity data of this system obtained by Rusinski & Lu (1999) for analysis. The radial velocity and light curves analysis was made with the latest version ofWilson program(1998) and the geometric and physical elements of the system are derived. By searching the simultaneous solutions of the system, we have determined the masses and radii of the components : 1.89(M_⊙) and 1.65(R_⊙) for the primary component; 0.93(M_⊙) and 1.23(R_⊙) for the secondary component. We estimated effective temperatures of 7030(K) for the primary and 6977(K) for the secondary component. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photometric study of an eclipsing binary in the field of M37

CCD photometric observations with B and V passbands were performed on the contact binary V3 in the field of open cluster M37. The solutions were obtained for data from both B and V passbands along with R passband given by Hartman et al.using the Wilson-Devinney code. The positive O'Connell effect was observed in all the three passbands and its associated cool spot parameters were derived. The results indicate that the spot parameters have not shown any significant variability during the last four years. The spot radius was found to be 40and located close to the equator of the secondary component. The absolute parameters of the system were derived using the empirical relations given by Gazeas et al.     

KR Cygni: a near-contact eclipsing binary?

In this study we present photometric observations of the eclipsing binary KR Cyg made in 1999 and 2000. The observations of the eclipsing binary KR Cyg have been carried out in B, V and R colours at the Ege University Observatory. A new seasonal light curves are presented. New times of minima and ephemerides are given. Based on a statistical analysis of the times of minima obtained by photoelectric photometry, the orbital period of the system is found to be constant. The photometric mass ratio of the system is well determined. The corresponding light curves were analyzed by the Wilson-Devinney code. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gravitational lensing in eclipsing binary stars

I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focusing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If not accounted for, this may lead to under-estimation of the radius of the white dwarf compared with that of its companion. I show that the effect is significant for plausible binary parameters, and that it leads to ∼25 per cent reduction in the transit depth in the system KPD 1930+2752. The reduction of eclipse depth is degenerate with the stellar radius ratio, and therefore cannot be used to establish the existence of lensing. A second-order effect of the light bending is to steepen the ingress and egress features of the secondary eclipse relative to the primary eclipse, although it will be difficult to see this in practice. I consider also binaries containing neutron stars and black holes. I conclude that, although relatively large effects are possible in such systems, a combination of rarity, faintness and intrinsic variability makes it unlikely that lensing will be detectable in them.     

Automated analysis of eclipsing binary light curves – II. Statistical analysis of OGLE LMC eclipsing binaries

In the first paper of this series, we presented EBAS – Eclipsing Binary Automated Solver, a new fully automated algorithm to analyse the light curves of eclipsing binaries, based on the ebop code. Here, we apply the new algorithm to the whole sample of 2580 binaries found in the Optical Gravitational Lensing Experiment (OGLE) Large Magellanic Cloud (LMC) photometric survey and derive the orbital elements for 1931 systems. To obtain the statistical properties of the short-period binaries of the LMC, we construct a well-defined subsample of 938 eclipsing binaries with main-sequence B-type primaries. Correcting for observational selection effects, we derive the distributions of the fractional radii of the two components and their sum, the brightness ratios and the periods of the short-period binaries. Somewhat surprisingly, the results are consistent with a flat distribution in log P between 2 and 10 d. We also estimate the total number of binaries in the LMC with the same characteristics, and not only the eclipsing binaries, to be about 5000. This figure leads us to suggest that  (0.7 ± 0.4)  per cent of the main-sequence B-type stars in the LMC are found in binaries with periods shorter than 10 d. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars. On the other hand, the binary frequency found by Hubble Space Telescope ( HST ) photometric searches within the late main-sequence stars of 47 Tuc is only slightly higher and still consistent with the frequency we deduced for the B stars in the LMC.     

First ground‐based photometry and light‐curve analysis of the eccentric eclipsing binary V744 Cas

The first ground‐based BVR photometric observations of the recently discovered eclipsing binary V744 Cas are presented. From these measurements, timings for two primary and one secondary minima have been calculated. The light curves of the system were analyzed by using the Wilson‐Devinney program. The analysis shows that the system is detached with two similar components of spectral type A2V, and the orbit is eccentric (e = 0.0662 ± 0.0005). The longitude of the periastron (ω) was found significantly different for two different light curves (ours and that of Hipparcos), which is strongly suggestive of an apsidal motion with a period of about 425 ± 68 yr. This makes V744 Cas an important candidate for studies of apsidal motions. The first estimate of the absolute dimensions place the system close to the terminal age of the main sequence (TAMS) in the HR diagram. The distance from the spectroscopic parallax (d = 740 ± 10 pc) was found to be slightly larger than the Hipparcos distance of d = 610 ± 400 pc. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mechanisms for eclipsing in exotic eclipsing systems

The stars ε Aur, KH 15D, and H 187 are utterly different in their fundamental characteristics. However, they share two important features: (1) prolonged eclipses are observed in all three and (2) there are no spectroscopic signs of a second component. The light curves of these objects are substantially similar, which may indicate a uniform mechanism for the eclipses. This article analyzes models for eclipsing in these objects proposed by different authors and discusses the problems associated with their application. __________ Translated from Astrofizika, Vol. 49, No. 4, pp. 553–571 (November 2006).     

Orbital period variation of the eclipsing binary system TT Herculis

New photoelectric UBV observations were obtained for the eclipsing binary TT Her at the Ankara University Observatory (AUO) and three new times of minima were calculated from these observations. The (O – C) diagram constructed for all available times of minima of TT Her exhibits a cyclic character superimposed on a quadratic variation. The quadratic character yields an orbital period decrease with a rate of dP /dt = –8.83 × 10^–8 day yr^–1 which can be attributed to the mass exchange/loss mechanism in the system. By assuming the presence of a gravitationally bound third body in the system, the analysis of the cyclic nature in the (O – C) diagram revealed a third body with a mass of 0.21M_⊙ orbiting around the eclipsing pair. The possibility of magnetic activity cycle effect as a cause for the observed cyclic variation in the (O – C) diagram was also discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Updated catalogue of the light curve solutions of contact binary stars

The catalogue of the light curve solutions of contact binary stars was updated. Based on the catalogue data we call the attention to a remarkable gap in the temperature distribution of contact binaries which remained unexplained. The absolute dimensions of the components were calculated in a reliable way. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Automated analysis of eclipsing binary light curves – I. EBAS – a new Eclipsing Binary Automated Solver with ebop

We present a new algorithm, Eclipsing Binary Automated Solver (EBAS), to analyse light curves of eclipsing binaries. The algorithm is designed to analyse large numbers of light curves, and is therefore based on the relatively fast ebop code. To facilitate the search for the best solution, EBAS uses two parameter transformations. Instead of the radii of the two stellar components, EBAS uses the sum of radii and their ratio, while the inclination is transformed into the impact parameter. To replace human visual assessment, we introduce a new 'alarm' goodness-of-fit statistic that takes into account correlation between neighbouring residuals. We perform extensive tests and simulations that show that our algorithm converges well, finds a good set of parameters and provides reasonable error estimation.     

A spectroscopic orbit for the two—Spectrum eclipsing binary RT Persei

Intensified Reticon spectra have been obtained at a high dispersion for the Algol system, RT Persei. They were measured by the cross-correlation technique. The spectroscopic elements, revised for the primary component and determined for the secondary for the first time, are: T₀ = HJD 2,446,038.9332, K₁ = 55.0, K₂ = 194.7, V₀ = −8.3 km/s. A mass ratio q = m₂/m₁ = 0.282 is deduced. A circular orbit is adopted. The spectrum of the primary is F5V, and the secondary is a subgiant. With the elements determined here and the published photometric parameters, the absolute dimensions of the binary are: A = 4.20, R₁ = 1.20, R₂ = 1.08 R; M₁ = 1.08, M₂ = 0.30 M.     

Study of the apsidal motion in the eclipsing binary MZ Lac

A series of highly accurate photoelectric observations of the eclipsing binary MZ Lac was obtained with a 48-cm AZT-14 reflector at the Tien-Shan High-Altitude Station of the Sternberg Astronomical Institute from 1985 to 2004 to study its apsidal motion. We constructed a consistent system of physical and geometrical parameters of the components and the binary’s orbit: we determined their masses (M₁ = 1.50M_⊙, M₂ = 1.29M_⊙), radii (R₁ = 1.86R_⊙, R₂ = 1.35R_⊙), luminosities (L₁ = 0.79L_⊙, L₂ = 0.45L_⊙), surface gravities (log_g1 = 4.06, log_g2 = 4.27), age (t = 1.9 × 10⁹ yr), and the distance to the binary (d = 510 pc). The binary exhibits apsidal motion with the period U_obs = 480 ± 40 yr, while its theoretically expected value is U_th = 450 ± 40 yr. Spectroscopic studies of MZ Lac and calculations of the absolute parameters of the components are required to test our conclusions.     

Photometric analysis of the eclipsing binary 2MASS 19090585+4911585

We report on observations of the eclipsing binary 2MASS 19090585+4911585 with the 25 cm auxiliary telescope of the University Observatory Jena. We show that a nearby brighter star (2MASS 19090783+4912085) was previously misclassified as the eclipsing binary and find 2MASS 19090585+4911585 to be the true source of variation. We present photometric analysis of VRI light curves. The system is an overcontact binary of W UMa type with an orbital period of (0.288374 ± 0.000010) d (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photometric solution of the eclipsing binary system EF Boötis

The EF Boo eclipsing binary system is studied in the context of optical light curves and radial velocity curves published in the literature. The best‐solution leads to an over‐contact configuration of W–subclass of WUMa systems with a fill‐out factor of 28%. Absolute parameters based on simultaneous solution of light and radial velocity curves are presented. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The MOA catalogue of eclipsing binary stars in the Small Magellanic Cloud

We present a catalogue of 167 eclipsing binary stars in the Small Magellanic Cloud (SMC) derived from the data base of time-series photometry for 400 000 SMC stars acquired by the Microlensing Observations in Astrophysics (MOA) project during 1997. We print coordinates, ephemerides, magnitudes and light curves for the 35 new detections; similar data and finding charts are available electronically for the whole catalogue. The majority of periods lie within the range 0.4 to 20 d; six systems are possibly eccentric while 14 are probably or certainly so. The majority of the newly identified systems lie in the outer regions of the SMC.