First photometric investigation of two short-period eclipsing binaries NSVS 7377756 and for UCAC3 276-106147

We present the first CCD sets of complete light curves for two W Ursae Majoris Systems, UCAC3 276-106147 and NSVS 7377756. These light curves are here analyzed and modelled using the latest version of the Wilson-Devinney Code. We found that UCAC3 276-106147 is a W-subtype shallow-contact eclipsing binary (fill-out factor 7.5%), with a mass ratio of q = 2.88 (1/q = 0.347), a small temperature difference between the components of about ΔT =200K. NSVS 7377756 is an H-subtype binary system with a high mass ratio of q = 1.09 (1/q = 0.947), a weak degree of contact factor f = 3.8% and a temperature difference between the components of ΔT = 398 K. The light curves of both the systems appear to be unspotted. By using our 4 and 7 times of minimum light and the 30 and 104 ToMs extract from the SWASP observations, respectively for UCAC3 276-106147 and NSVS 7377756, the orbital periods are here revised. The elements obtained from this analysis are used to compute the physical parameters of the systems combining our photometric solution with the 3-D correlation obtained for contact binaries by Gazeas (2009). Based on these estimated parameters the evolutionary state of the components of the systems is investigated and discussed.     

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.     

The K spectral type contact binary NSVS 1557555: Photometric solution and preliminary elements

We present the first CCD sets of complete light curves for the W Ursae Majoris system NSVS 1557555.The observations were performed in the B, V and I_c bands using the 0.25  m telescope of the Stazione Astronomica Betelgeuse Northern Italy, during 8 nights in October and November 2016.Based on our new eleven Time of Minima (ToM), and two recent ones found in bibliography, the short orbital period of the system is confirmed and revised to P = 0.2725163 days .A reasonable fit of the synthetic light curves of the data indicate that NSVS 1557555 is a late-type (K1+K3) shallow contact binary system of W-Subtype of the W Ursae Majoris systems, with a mass ratio of q = 1.8, a degree of contact factor f = 12.5%, a temperature difference between the components of 240K and inclination i = 85°.The light curves show asymmetries at the maxima with the maximum at phase 0.75 higher the other one (inverse O’Connell effect).To explain the light asymmetries we used a model that involves an hot spotted region on the surface of the cooler star.The definitive solution is only possible with a large amount of third light (L₃ = 0.58 in B Filter). It may come from a hot tertiary component.The absolute dimensions of the system are estimated. From the logM-logL diagram it is seen that both components of NSVS 1557555 follow the general pattern of the W subtype W Ursae Majoris systems.The orbital angular momentum is compared with those of other W UMa type binaries and is normal.     

NSVS 7051868: A system in a key evolutionary stage. First multi-color photometric study

The first CCD photometric complete light curves of the eclipsing binary NSVS 7051868 were obtained during six nights in January 2016 in the B, V and I_c bands using the 0.25 m telescope of the Stazione Astronomica Betelgeuse in Magnago, Italy.These observations confirm the short period (P = 0.517 days) variation found by Shaw and collaborators in their online list (http://www.physast.uga.edu/~jss/nsvs/) of periodic variable stars found in the Northern Sky Variability Survey.The light curves were modelled using the Wilson–Devinney code and the elements obtained from this analysis are used to compute the physical parameters of the system in order to study its evolutionary status.A grid of solutions for several fixed values of mass ratio was calculated.A reasonable fit of the synthetic light curves of the data indicate that NSVS 7051868 is an A-subtype W Ursae Majoris contact binary system, with a low mass ratio of q = 0.22, a degree of contact factor f = 35.5% and inclination i = 85°. Our light curves shows a time of constant light in the secondary eclipse of approximately 0.1 in phase. The light curve solution reveals a component temperature difference of about 700 K. Both the value of the fill-out factor and the temperature difference suggests that NSVS 7051868 is a system in a key evolutionary stage of the Thermal Relaxation Oscillation theory.The distance to NSVS 7051868 was calculated as 180 pc from this analysis, taking into account interstellar extinction.     

Photometric investigation of two contact binaries in the young open cluster NGC 957

We present V- and R- band time-series CCD photometry of two contact binaries in the region of the young open cluster NGC 957. The two eclipsing binaries were discovered by Bukowiecki et al., 2009. OEJV 112, 1 and named as V4 and V5, respectively. In the present paper, the first detailed studies of the two contact binary systems are carried out. Firstly, based on the light curves, 28 times of minimum light were detected for V4 and 21 times of minimum light for V5, respectively. Secondly, the orbital periods of V4 and V5 were redetermined as P_V4 = 0.40032(5) days and P_V5 = 0.30752 (4)days, respectively. The photometric solutions were analyzed by using Wilson Decinny Code. The results reveal that both V4 and V5 are W UMa-type contact binaries with a degree of f_V4 = 31(± 1)% and f_V5 = 65(± 1)%. The mass ratios were determined to be q_V4 = 0.30 and q_V5 = 0.19. For V5, the well known O’Connell effect was detected in the dataset, which effect can be explained by employing a dark spot placed on the more massive primary component. Finally, based on the distances of the two contact binaries, which were calculated by using an relation given by Gettel et al., the two contact binaries are judged to be foreground stars in the open cluster NGC 957.     

Global parameters of the totally-eclipsing W UMa stars NSVS 6673994, NSVS 4316778, PP Lac and NSVS 1926064

Photometric observations of four totally-eclipsing W UMa binaries, NSVS 6673994, NSVS 4316778, PP Lac and NSVS 1926064, are presented. Their global parameters were determined from the light curve solutions and GAIA distances. The main results are as follows: (i) NSVS 6673994, NSVS 4316778 and PP Lac are of W subtype while NSVS 1926064 is of A subtype; (ii) The mass ratios of NSVS 4316778 and NSVS 1926064 are close to the lower mass-ratio limit; (iii) NSVS 4316778 has double contact configuration while NSVS 1926064 is in deep contact; (iv) The changes of the PP Lac period seem cyclic and are accompanied with episodes of essentially constant value; (v) The relations between the global parameters of the four W UMa stars differ considerably from those of Main Sequence (MS) stars. The deviations of the radii, temperatures and luminosities of the stellar components from those of MS stars with the same masses are bigger for the two targets with extremely small mass ratio.     

A photometric study of a new short period eclipsing sdB binary NSVS 07826147

NSVS?07826147 and NSVS?04818255 were suspected as possible eclipsing sdB binary systems by Kelley and Shaw. In order to investigate the short period eclipsing sdB binaries, we have listed them as our observing targets and began to monitor it from March 2009. Till now, we have obtained four complete CCD light curves and 16 high precise times of light minimum of NSVS?07826147. All light curves show strong reflection and a very narrow eclipse, which implies that NSVS?07826147 should be a new short period eclipsing sdB binary. For the system NSVS?04818255, no eclipse character was found in the light curves according to our observations. However, we found that a star near NSVS?04818255 is a close binary system with a period of about 0.32498 days. Up to now, only seven short period eclipsing sdB binary systems have been found, including NSVS?07826147. With the new precise epochs obtained by us, the new period of this system is derived as 0.16177046(5) days, which can be used to predict the epochs of light minimum. Furthermore, the light curves of NSVS?07826147 are analyzed using the Wilson–Van Hamme code and the testing photometric solutions are presented and discussed.     

Photometric Studies of Twelve Deep, Low-mass Ratio Overcontact Binary Systems

The formations of the blue straggler stars and the FK Com-type stars are unsolved problems in stellar astrophysics. One of the possibilities for their formations is from the coalescence of W UMa-type overcontact binary systems. Therefore, deep (f > 50%), low-mass ratio (q < 0.25) overcontact binary stars are a very important source to understand the phenomena of Blue Straggler/FK Com-type stars. Recently, 12 W UMa-type binary stars, FG Hya, GR Vir, IK Per, TV Mus, CU Tau, V857 Her, V410 Aur, XY Boo, SX CrV, QX And, GSC 619-232, and AH Cnc, were investigated photometrically. Apart from TV Mus, XY boo, and GSC 619-232, new observations of the other 9 binaries were obtained. Complete light curves of the 10 systems, FG Hya, GR Vir, IK Per, TV Mus, CU Tau, V857 Her, GSC 619-232, V410 Aur, XY Boo, and AH Cnc, were analyzed with the 2003 version of the W-D code. It is shown that all of those systems are deep (f > 50%), low-mass ratio (q < 0.25) overcontact binary stars. We found that the system GSC 619-232 has the highest degree of overcontact (f = 93.4%). The derived photometric mass ratio of V857 Her, q = 0.0653, indicates that it is the lowest-mass ratio system among W UMa-type binaries.Of the 12 sample stars, long-term period changes of 11 systems were found. About 58% (seven) of the sample binaries show cyclic period oscillation. No cyclic period changes were discovered for the other 5 systems, which may be caused by the short observational time interval or by insufficient observations. Therefore, we think that all W UMa-type binary stars may contain cyclic period variations. By considering the long-term period changes (both increase and decrease) of those binary stars, we proposed two evolutionary scenarios evolving from deep, low-mass ratio overcontact binaries into Blue Straggler/FK Com-type stars.     

Photometric observations of the W UMa stars CSS J113505.5+332031, ASAS J142124+1813.1 and HR Boo

Multicolor photometric observations of the W UMa binaries CSS J113505.5+332031, ASAS J142124+1813.1 and HR Boo are presented. They led to improvement of the orbital periods of CSS J113505.5+332031 and HR Boo. The light curve solutions revealed that all the targets are overcontact binaries with moderate fill-out factors whose components are of G and K spectral types. ASAS J142124+1813.1 and HR Boo undergo total eclipses and their mass ratios are well-determined. The small mass ratio of ASAS J142124+1813.1 puts this target in the list of W UMa binaries with extreme low mass ratios. The possible solutions for the partially-eclipsed binary CSS J113505.5+332031 and their precision are discussed in detail. Masses, radii and luminosities of the target components were estimated by our light curve solutions and GAIA distances.     

New CCD photometry of the eclipsing binary system V1067 Her

We present a new set of CCD photometric observations for the short period eclipsing binary 1SWASP J1743 (= V1067 Her). We have determined the available times of light minima and two new linear and quadratic ephemerides have been obtained. The photometric solutions for the system have been performed using Wilson and Devinney Code. The 3D and fill out configuration revealed that V1067 Her is an over contact W UMa binary with relatively low fill-out factor of about 16%.We investigated the period variation for the system. It showed a strong evidence of period changes by using the (O-C) residual diagram method and we have concluded long-term orbital period decrease rate dP/dt= −3.0 × 10⁻⁷ d/yr, corresponding to a time scale 8.6 × 10⁵ yr. Such period decrease in the A-type W UMa systems is usually interpreted to be due to mass transfer from the more to the less massive component.     

First photometric analysis of the two EW binaries ZTF J214226.88+435827.1 and KAO-EGYPT J214216.38+440015.1

The EW-type eclipsing binaries are strongly interacting systems known to have often both component stars filling their crucial Roche lobes and having a common envelope. We present new BVRI light curves of the eclipsing binaries ZTF J214226.88+435,827.1 (ZTF21+43) and KAO-EGYPT J214216.38+440,015.1 (KAO21+44) based on CCD observations acquired with the 1.88-m Kottamia Astronomical Observatory (KAO) at Newtonian and Cassegrain telescope focus. The modeling results show that these two systems are to be W UMa contact binaries belonging to EW subtypes. All the light curves show the inverse O'Connell effect. We computed new ephemeris for each system using our times of minima and that available in the literature. Using our new times of minima and epochs for both systems from all available observations, the orbital period changes of these structures are studied for our systems. Using the PHOEBE package, a preliminary determination of the two systems' photometric orbital and physical parameters has been present. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R), M-L, and T_eff-L diagrams to test their evolutionary status.     

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.     

The eclipsing binary star V380 Gem: First V and Rc light curve analysis and estimation of its absolute elements

We obtained complete V and R_c light curves of the eclipsing binary V380 Gem in 2012. With our data we were able to determine six new times of minimum light and refine the orbital period of the system to 0.3366088 days. The 2003 version of the Wilson–Devinney code was used to analyze the light curves in the V and R_c bands simultaneously. It is shown that V380 Gem may be classified as an W-type W Ursae Majoris system with a high mass ratio q = 1.45, a degree of contact f = 10.6% the same temperature for both the components (ΔT = 10 K) and an orbital inclination of i  = 81.5°. Our observations show symmetric light curves in all passbands with brightness in both maxima at the same level. The absolute dimensions of V380 Gem are estimated and its dynamical evolution is inferred.     

Absolute parameters of the W UMa binaries CSS J223614+311343, V523 Aur and V783 And

Photometric BVR_c observations of the stars CSS J223614+311343, V523 Aur and V783 And were carried out and their absolute parameters (masses, radii and luminosities) were determined based on light curve modeling and Gaia distances. The main results are: (i) The components of CSS J223614+311343 and V783 And are of K spectral type while those of V523 Aur are G stars; (ii) The three systems have middle fillout factors 0.20–0.29; (iii) CSS J223614+311343 and V783 And are of A-subtype while V523 Aur is of W-subtype; (iv) The common target masses are near the lower mass limit for the known W UMa binaries; (v) The smaller in size (and less massive) components of all targets locate above the MS band of the evolutional diagrams while the bigger components are within the MS band. The only exception is the bigger component of V523 Aur that is also above the MS band. This result was attributed to the W-subtype of the target.     

An observational study of the high-amplitude δ Scuti star V367 Cam

CCD observations of V367 Cam, a high-amplitude δ Scuti star, were carried out in both V and R band on October 22 and 23 and November 4, 2016. By using the new observed maximum times and the previously reported epochs, a new ephemeris is obtained. Fourier analysis of the light curves yields the main frequency f1 = 8.2242 d ⁻¹ and its second harmonic as 2f1 = 16.4062 d ⁻¹. The pulsation constant specifying the oscillation characteristics of pulsating stars is calculated from physical parameters of V367 Cam. We obtained Q = 0.03814 ± 0.00409, which demonstrates this star pulsates in single radial fundamental mode. With the derived physical parameters, the evolution status of V367 Cam is determined and also it is shown on H-R diagram against other δ Scuti stars. Furthermore, we made a count of mono-periodic HADS, which are expected to be decreasing in number and turned to be multiperiodic in the advent of high precision photometry and extended data.     

Light curve solutions of six eclipsing binaries at the lower limit of periods for W UMa stars

Photometric observations are presented in V and I bands of six eclipsing binaries at the lower limit of the orbital periods for W UMa stars. Three of them are newly discovered eclipsing systems. The light curve solutions reveal that all shortperiod targets are contact or overcontact binaries and six new binaries are added to the family of short-period systems with estimated parameters. Four binaries have components that are equal in size and a mass ratio near 1. The phase variability shown by the V-I colors of all targets may be explained by lower temperatures on their back surfaces than those on their side surfaces. Five systems exhibit the O'Connell effect that can be modeled by cool spots on the side surfaces of their primary components.The light curves of V1067 Her in 2011 and 2012 are fitted by diametrically opposite spots. Applying the criteria for subdivision of W UMa stars to our targets leads to ambiguous results.     

Photometric study of five kepler contact binaries

A lot of data in time domain were obtained by the Kepler mission, including many contact binaries. Long-term observation lets us obtain more information about the short time scale variation in their light curves or in their orbital periods. Unfortunately, the exposure time is too long (most of them are 30 minutes). Hence, many variations in light curves are smoothed. To avoid this problem, we analyzed some Kepler contact systems with both long-cadence mode and short-cadence mode data. Using the latest version of the Wilson-Devinney code, we obtained the physical parameters of a batch of contact binaries and find out four targets(KIC 5123176, KIC 5296877, KIC 8496820, KIC 9776718) have low mass ratios (q  <  0.25) and one target (KIC 7950962) has a mass ratio very close to unit.     

Investigation of Times of Minima of Selected Early-Type Eclipsing Binaries

New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus.