First analysis of eight Algol-type binaries: EI Aur,XY Dra,BP Dra,DD Her,VX Lac,WX Lib,RZ Lyn,and TY Tri

The available photometry from the online databases were used for the first light curve analysis of eight eclipsing binary systems EI Aur, XY Dra, BP Dra, DD Her, VX Lac, WX Lib, RZ Lyn, and TY Tri. All these stars are of Algol-type, having the detached components and the orbital periods from 0.92 to 6.8 days. For the systems EI Aur and BP Dra the large amount of the third light was detected during the light curve solution. Moreover, 468 new times of minima for these binaries were derived, trying to identify the period variations. For the systems XY Dra and VX Lac the third bodies were detected with the periods 17.7, and 49.3 years, respectively.     

First analysis of eight Algol-type systems: V537 And,GS Boo,AM CrB,V1298 Her,EL Lyn,FW Per,RU Tri,and WW Tri

Analyzing available photometry from the Super WASP and other databases, we performed the very first light curve analysis of eight eclipsing binary systems V537 And, GS Boo, AM CrB, V1298 Her, EL Lyn, FW Per, RU Tri, and WW Tri. All of these systems were found to be detached ones of Algol-type, having the orbital periods of the order of days. 722 new times of minima for these binaries were derived and presented, trying to identify the period variations caused by the third bodies in these systems.     

Period studies of classical Algol-type binaries II: UX Leo,RW Mon,EQ Ori,XZ UMa and AX Vul

This study presents an investigation of the orbital period variations of five Algol type binaries, UX Leo, RW Mon, EQ Ori, XZ UMa and AX Vul based on all available minima times. The O–C diagrams of all systems exhibit a periodic variation superimposed on a downward parabolic segment. The mass loss due to magnetic braking effect in the cooler components is assumed to account for the parabolic variation with a downward shape, while it is suggested that the light-time effect (LITE) due to an unseen component around the eclipsing binaries explains the tilted sinusoidal changes in their O–C diagrams. The orbital period decrease rates for the systems are estimated as approximately between about 0.7 and 2.5 s per century. It is clearly seen that mass loss effect is more dominant than the expected mass transfer for classical Algols in this study. The minimum mass of the probable third bodies around the eclipsing pairs was calculated to be ?0.5 M_⊙ except for UX Leo, in which it was estimated to be approximately 0.9 M_⊙. In order to search for third lights in the light curves of five systems, the V-light curves of the systems were analyzed and their physical and photometric parameters were determined. For UX Leo, a significant third light contribution was determined. We found a very small third light that can be tested using multi-color light curves, for RW Mon, EQ Ori and XZ UMa, while a third light for AX Vul could not be exposed.     

New eccentric eclipsing binary in triple system: SY Phe

Analyzing available photometry from Hipparcos, ASAS, Pi of the sky and Super WASP, we found that the system SY Phe is a detached eclipsing binary with similar components and orbital period about 5.27089 days. It has a slightly eccentric orbit, however the apsidal motion is probably very slow. The system undergoes an additional photometric variation on longer time scales superimposed on the eclipsing light curve. It also contains one distant component, hence the third light was also considered.     

A comprehensive study of six Algol type binaries

CCD light curves of the Algol type eclipsing binaries DP Cep, AL Gem, FG Gem, UU Leo, CF Tau and AW Vul were analysed using the Wilson–Devinney code and new geometric and absolute parameters were derived. Due to cyclic apparent orbital period changes of the systems, probably caused by the Light-Time Effect, the contribution of a third light was taken into account in the light curve solution. All the reliable timings of minima found in the literature were used to study the period variations and search for the presence of a tertiary component in the systems. A comparison between the parameters of the third body derived from the light curve and orbital period analyses is also discussed. Moreover, the absolute parameters of the eclipsing binary components were also used to determine their current evolutionary state.     

The first light curve solutions and period study of two contact binary systems: V1370 Tau and QQ Boo

The first light curve solutions of the binary systems V1370 Tau and QQ Boo are presented. The periodic changes are calculated, and a new ephemeris presented for each of these two binary systems. O-C analysis is performed using the MCMC method in OCFit code. The changing rate of period was measured as dP/dt= 0.2423 days/year for V1370 Tau and dP/dt= -0.1363 days/year for QQ Boo. The light curve solutions suggest that V1370 Tau is a weak-contact eclipsing binary system with a photometric mass ratio q = 0.829, and that the corresponding fillout factor is 11.06%. Furthermore, it is suggested that the QQ Boo binary system is also a weak-contact W UMa eclipsing binary with a photometric mass ratio q = 0.831, and that its fillout factor equals 10.26%. The light curve solutions require cold spots. Utilizing the Wilson-Devinney code the photometric and geometric parameters of the systems are determined. The distance of both V1370 Tau and QQ Boo are calculated according to the estimated absolute parameters as 159.95 ± 23 pc and 309.03 ± 25 pc, respectively, which are in a good agreement with the distance values derived from the Gaia DR2 parallax within one standard deviation. Moreover, the positions of their components on the H-R diagram are represented.     

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%(±0.8%). 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 _⊙ and P ₃=87.0 yr. On the contrary, assuming continuous period changes of the eclipsing pair the orbital period of tertiary is 37.75 yr and its mass is about 0.278M _⊙. Both of the cases suggest the presence of an unseen third component in the system.     

The Algol-type eclipsing binaries RW CrB and VZ Leo: new RI photometric study and search for pulsations

In this study we present the new R and I light curve solutions for the eclipsing binary systems RW CrB and VZ Leo, which for VZ Leo is the first one in the literature. Our new observations have been analyzed using the Wilson-Devinney code from which new geometric and photometric elements are derived. The geometry of both stars is that of a semi-detached binary system where the secondary component fills its Roche lobe while the primary component is well inside. In the case of RW CrB, asymmetry in the light curve was explained by a spot model. The orbital period changes of both systems were studied and the results indicated a period decrease which can be explained by angular momentum loss. We also investigated the possibility of pulsations of the primary components since these systems are mentioned as candidates of δ Sct type pulsation. However, a time-series analysis of the residual curves in the filter I does not indicate any evidence of periodic light variation for both systems. Finally, we compared the results obtained for both binary stars to those of similar systems.     

First light curve analyses of binary systems AO Aqr,CW Aqr and ASAS 012206-4924.7

Using the data from the public database of the All Sky Automated Survey (ASAS) we performed the very first light curve analyses of the three eclipsing binary systems AO Aqr, CW Aqr and ASAS 012206-4924.7. The physical parameters of the systems were determined by the PHOEBE (Prša and Zwitter, 2005) software. From an analysis of the ASAS data it was concluded that AO Aqr was found to be a contact binary system while CW Aqr and ASAS 012206-4924.7 were found to be near-contact and detached binaries, respectively. Finally, the locations of the components, corresponding to the estimated physical parameters, in the HR diagram were also discussed.     

A γ Doradus candidate in eclipsing binary BD And?

The BVR photometric light curves of the eclipsing binary BD And were obtained in 2008 and 2009. We estimated the mass ratio of the system as 0.97 and the photometric solutions were derived. The results show that BD And is a detached binary system, whose components have a little temperature difference of about 40 K. By analyzing photometric available light minimum times, we also derived an update ephemeris and found for the first time a possible periodic oscillation with an amplitude of 0.011 days and a period of 9.6 years. The results indicate that the periodic oscillation could be caused by a third component physically attached to the eclipsing binary. After removing the light variations due to the eclipses and proximity effects, the light-curve distortions are further explained by the pulsation of the primary component with a dominant period of ∼1 day. In accordance with the position of the primary component on the Hertzsprung–Russell diagram and its pulsation period, the primary component of BD And could be an excellent γ Doradus candidate. It is rarely phenomenon that a component of the eclipsing binary system is a γ Doradus variable.     

The first light curve solutions and period changes of EW Psc and HN Psc

The first light curve solutions of the stars EW and HN in the Pisces constellation are presented. Photometry, and its’ periodic changes are calculated and discussed. The analysis of the O-C diagram is done by the MCMC approach in the OCFit code and a new ephemeris is provided for the two binary systems. The results show that EW Psc is a near contact eclipsing binary system with a photometric mass ratio q = 0.587, and the fillout factor is -0.034 and -0.018 for the primary and secondary components, respectively. The solution results also show that the system HN Psc is a weak-contact W UMa eclipsing binary with a photometric mass ratio q = 0.853, and with a fillout factor of 5.6%. The light curves solutions required a cold spot to account for the O'Connell effect.     

Long-Term Study of the Starspot Activity on the Eclipsing Short-Period RS Canum Venaticorum Star UV Piscium

We present optical photometry of the short period eclipsing RS CVn system, UV Piscium for the years 1966–1984. After removing the spot effects from the light curves of Vivekananda Rao and Sarma (1981), we analyzed the cleaned data to obtain system parameters. For each light curve, we model the distortion waves in order to study the behaviour of star spots in this system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photometry of the three eclipsing novalike variables EC 21178-5417, GS Pav and V345 Pav

As part of a project to better characterize comparatively bright, yet little studied cataclysmic variables time resolved photometry of the three eclipsing novalike variables EC 21178-5417, GS Pav und V345 Pav is presented. Previously known orbital periods are significantly improved and long-term ephemeris are derived. Variations of eclipse profiles, occurring on time scales of days to weeks, are analyzed. Out of eclipse the light curves are characterized by low scale flickering superposed on more gradual variations with amplitudes limited to a few tenths of a magnitude and profiles which at least in EC 21178-5417 and GS Pav roughly follow the same pattern in all observed cycles. Additionally, signs for variations on the time scale of some tens of minutes are seen in GS Pav, most clearly in two subsequent nights when in the first of these a signal with a period of 15.7 min was observed over several hours. In the second night variations with twice this period were seen. While no additional insight could be gained on quasi periodic oscillations (QPOs) and dwarf nova oscillations in EC 21178-5417, previously detected by Warner et al. (2003), and while such oscillations could not be found in V345 Pav, stacked power spectra of GS Pav clearly reveal the presence of QPOs over time intervals of several hours with periods varying between 200 s and 500 s in that system.     

First XMM-Newton observations of strongly magnetic cataclysmic variables – II. Timing studies of DP Leo and WW Hor

XMM-Newton was used to observe two eclipsing, magnetic cataclysmic variables, DP Leo and WW Hor, continuously for three orbital cycles each. Both systems were in an intermediate state of accretion. For WW Hor we also obtained optical light curves with the XMM-Newton Optical Monitor and from ground-based observations. Our analysis of the X-ray and optical light curves allows us to constrain physical and geometrical parameters of the accretion regions and derive orbital parameters and eclipse ephemerides of the systems. For WW Hor we directly measure horizontal and vertical temperature variations in the accretion column. From comparisons with previous observations we find that changes in the accretion spot longitude are correlated with the accretion rate. For DP Leo the shape of the hard X-ray light curve is not as expected for optically thin emission, showing the importance of optical depth effects in the post-shock region. We find that the spin period of the white dwarf is slightly shorter than the orbital period and that the orbital period is decreasing faster than expected for energy loss by gravitational radiation alone.     

New CCD photometry and light curve analysis of two WUMaBinaries: 1SWASP J133417.80+394314.4 and V2790 Orion

We present a new multicolor CCD photometry and light curve analysis of two eclipsing binary systems, 1SWASP J133417.80 + 394314.4 and V2790 Orion. The photometric solutions for both binaries were carried out using the updated version of the Wilson– Devinney code. The results showed that first systems is A- type W UMa with mass ratios q = 0.158 while the second system is W- type with q = 3.2. The systems show over contact configuration with fill-out factors of f = 43% and 14% respectively. We calculated the orbital and absolute physical parameters for both systems and investigated their evolutionary state.     

Eclipsing Binaries Showing Light–Time Effect

Four eclipsing binaries, which show apparent changes of period, have been studied with respect to a possible presence of the light–time effect. With a least squares method we calculated new light elements of these systems, the mass function of the predicted third body, and its minimum mass. We discuss the probability of the presence of such bodies in terms of mass function, changes in radial velocity and third light in solution of light curves.     

2XMMi J225036.9+573154 – a new eclipsing AM Her binary discovered using XMM–Newton

We report the discovery of an eclipsing polar, 2XMMi J225036.9+573154, using XMM–Newton . It was discovered by searching the light curves in the 2XMMi catalogue for objects showing X-ray variability. Its X-ray light curve shows a total eclipse of the white dwarf by the secondary star every 174 min. An extended pre-eclipse absorption dip is observed in soft X-rays at  φ= 0.8–0.9  , with evidence for a further dip in the soft X-ray light curve at  φ∼ 0.4  . Further, X-rays are seen from all orbital phases (apart from the eclipse) which make it unusual amongst eclipsing polars. We have identified the optical counterpart, which is faint  ( r = 21)  , and shows a deep eclipse (>3.5 mag in white light). Its X-ray spectrum does not show a distinct soft X-ray component which is seen in many, but not all, polars. Its optical spectrum shows Hα in emission for a fraction of the orbital period.     

Hunting for overlooked eccentric eclipsing binaries from ASAS-3 survey

We present the results of searching for new candidates of eclipsing binaries with eccentric orbits in the ASAS Catalog of Variable Stars (ACVS) using publicly available data from the All Sky Automated Survey (ASAS) and the Transiting Exoplanet Survey Satellite (TESS). Unsupervised machine learning techniques were applied to find anomalies among the light curves of eclipsing binaries. The light curves modeling were performed using JKTEBOP code. The pulsation analysis was done with FAMIAS. We identified 19 new eclipsing binary candidates with non-zero eccentricities in the ACVS, including 10 candidates with eccentricities e ≥ 0.1. Estimates of eccentricities are given. We also report on possible presence of the small-amplitude stellar pulsations at least in two of the reported systems.     

Catalog of W UMa type binary systems with additional components based on eclipsing time variations

A catalog of W UMa type eclipsing binary systems with tertiary components based on eclipse timing diagrams is presented listing the physical and orbital parameters (including third body parameters) of 150 W UMa type eclipsing binaries.In this study, the (O–C) diagrams of nine sample W UMa type eclipsing binary systems, based on the most reliable timings of minima in the literature, are analyzed to obtain the third-body parameters and significant statistical results are presented from the data in the catalog.     

New CCD photometry for the extreme lower mass-ratio binary AW Ursae Majoris

This paper presents charge-couple device (CCD) photometric observations for the eclipsing binary AW UMa. The V-band light curve in 2007 was analyzed using the 2003 version of the Wilson–Devinney code. It is confirmed that AW UMa is a total eclipsing binary with a higher degree of contact f=80.2% and a lower mass ratio of q=0.076. From the (O−C) curve, the orbital period shows a continuous period decrease at a rate of dP/dt=−2.05×10⁻⁷ d yr⁻¹. The long-term period decrease suggested that AW UMa is undergoing the mass transfer from the primary component to the secondary one, accompanied by angular momentum loss due to mass outflow L ₂. Weak evidence indicates that there exists a cyclic variation with a period of 17.6 yr and a small amplitude of A=0. ^d 0019, which may be attributed to the light-time effect via the third body. If the existence of an additional body is true, it may remove a great amount of angular momentum from the central system. For this kind of contact binary, as the orbital period decreases, the shrinking of the inner and outer critical Roche lobes will cause the contact degree f to increase. Finally, this kind of binary will merge into a single rapid-rotation star.