Photometric investigation of eight ultra-short period eclipsing binaries from OGLE

We performed a detailed photometric analysis of eight ultra-short period eclipsing binaries(USPEBs) using the Wilson-Devinney method. We present the modeled light curves and derived photometric solutions. The USPEBs with period(P)≤0.21 d considered in our study belong to W-subtype having shallow contact factor(f)～20%, high mass ratio(q)～0.7 and later spectral types. The absolute parameters for these short-period binaries were derived applying empirical relations. We discuss the evolutionary stage of these USPEBs using the mass-radius, color-density and period-color diagrams. The objects showed poor metallicities, and some objects were even found to be existing around fully convective limits. The period distribution of USPEBs exhibited a sharp cut-off at 0.22 d; however, we observed significant deficits for our objects in the literature. We examined the statistics of USPEBs studied to date(in terms of the distribution of period, mass ratio and component temperatures of USPEBs) and observed that a dominant distribution of component temperatures for these USPEBs was towards lower temperatures.     

Ten CoRoT eclipsing binaries: Photometric solutions

Ten eclipsing binaries, identified in the scope of the CoRoT Space Mission, were selected for analysis. The photometric light curves were processed and analyzed, resulting in the first study of eclipsing binary candidates with their possible photometric solution, in the context of the above-mentioned Space Mission. The selected targets are detached and overcontact systems, for which we computed 2MASS temperatures, in addition to different physical parameters, including orbital period, orbit inclination angle, and temperatures, radius and luminosity ratios. This study reveals a large diversity of eclipsing binary systems obtained from the CoRoT data.     

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.     

Synthetic light curve solutions for the short-period eclipsing binaries ST Aqr,DO Cas,and TX Cet

Synthetic light curve solutions of the short-period binary systems ST Aqr, DO Cas, and TX Cet are presented. Their evolutionary state is briefly discussed.     

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)     

Photometric analysis of two eclipsing binaries in the magellanic clouds

B, V andI light curves of the eclipsing binaries HV12634 in the LMV, and HV2208 in the SMC (cf. Westet al., 1992), have been analysed with the aid of optimal curve-fitting techniques. Parameter derivation involves a successive approximations procedure. The results of this are combined with a standard mass:luminosity relation to explore tentative absolute parameters. The combined evidence shows some disparity with standard MS-like models. It also demonstrates some relative insensitivity of photometric analysis, in isolation, to elucidate clear facts on such possibly atypical, remote, hot stars. Auxilliary spectroscopic data are required to resolve remaining ambiguities.     

Light curve solutions of the ultrashort‐period Kepler binaries

We carried out light‐curve solutions of the ultrashort‐period binaries with MS components observed by Kepler. All six targets turned out almost in thermal contact with contact or slightly overcontact configurations. Two of them, KID 4921906 and KID 6309193, are not eclipsing but reveal ellipsoidal and spot variability. One of the components of KID 8108785 exhibits inherent, quasi‐sinusoidal, small‐amplitude variability. KID 12055255 turned out tobe a very rare case of ultrashort‐period overcontact binary consisting of two M dwarfs. Our modeling indicated that the variability of KID 9532219 is due to eclipses but not to δ Sct pulsations as it was previously supposed. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photometric solutions of some contact ASAS binaries

We present the first light curve solution of 6 contact binary systems which are chosen from the ASAS catalog. The photometric elements and the estimated absolute parameters of all systems are obtained with the light curve analyses. We calculated the values of degree of contact for the systems. The location of the targets on the Hertzsprung–Russell diagram and the mass–radius plane is compared to the other well-known contact binaries and the evolutionary status of the systems are also discussed.     

Photometric study of three ultrashort-period contact binaries

We carried out high-precision photometric observations of three eclipsing ultrashort-period contact binaries (USPCBs). Theoretical models were fitted to the light curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: (a) 1SWASP?J030749.87?365201.7, \(q=0.439\pm0.003\), \(f=0.0\pm3.6\%\); (b) 1SWASP?J213252.93?441822.6, \(q=0.560\pm0.003\), \(f=14.2\pm1.9\%\); (c) 1SWASP?J200059.78+054408.9, \(q=0.436\pm0.008\), \(f=58.4\pm1.8\%\). The light curves show O’Connell effects, which can be modeled by the assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the \(I\)-band light curves of 1SWASP?J030749.87?365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with \(P < 0.24\) day. Thus, we found that most of them (17 of 28) are in shallow contact (i.e. fill-out factors \(f<20\%\)). Only four USPCBs have deep fill-out factors (i.e. \(f>50\%\)). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP?J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP?J030749.87?365201.7 is a zero contact binary in thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory.     

Orbital period investigation of some short-period sdB-type eclipsing binaries

Analysis of over 15 years of V-band and Wing three filter near-IR photometry of the bright M5Ib-II supergiant has been carried out. Wavelet analysis of these data reveals that the star pulsates with several complicated oscillation modes. Different time scales of variability are identified, and with the aid of discrete Fourier analysis, depending on the filter, up to seven significant pulsation modes are identified and their frequencies and amplitudes extracted. The Long Secondary Period (LSP) with a mean period of ～1343 d has been identified, as well as other periods of the order of ～125 d. The longer period appears to be attributed to the radial pulsational mode, while the various peaks near ～125 d appear to arise from stochastically excited p-modes. After removing the light contribution of the 5th magnitude binary companion and calibrating the intermediate-band photometry to the Wing photometric system, TiO (719 nm) and near-IR (B-C) Wing color indices were formed. These indices have been calibrated with T _eff, while the Wing-C bandpass (1025 nm) serves as a proxy for bolometric magnitude and was transformed to approximate m _bol. Finally, the derivation of the variations in the star’s temperature, luminosity and radius is straightforward.     

Evaluation of the light changes for distorted eclipsing binaries

This paper discusses a method for improving on the numerical evaluation of the light changes exhibited by a distorted eclipsing binary system.In the theory formulated by Kopal (1959), certain boundary integrals due to the distortion of both components have been calculated in terms of the Appell hypergeometric series of the first kind. The values of the four parameters appearing in these series differ according as to whether one is dealing with a partial or an annular eclipse.To accelerate the numerical evaluation of the light changes one should avoid recomputing such infinite series for contiguous values of the parameters. This can be achieved by making use of certain recursion formulae which hold for the foregoing series.We have provided here a procedure that yields forty-eight recursion formulae for the Appell hypergeometric series and have specifically calculated four new independent recursion formulae relevant to the astrophysical problem.     

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 the W UMa eclipsing binaries VW LMi and BX Dra

New ephemeris and the absolute parameters—masses, radii and luminosities—of the contact systems VW LMi and BX Dra have been obtained, by means of the analysis of the minima data available in the literature (for the determination of the ephemeris) and combining the previously published spectroscopic information and the results of the Wilson-Devinney method using photometric data (for the determination of the absolute parameters). The VW LMi O−C analysis confirms the multiplicity of the system detected previously from the spectroscopic data. Masses of the VW LMi contact system primary and secondary components are 1.67 ± 0.02M _⊙ and 0.70 ± 0.02M _⊙, respectively. The corresponding radii are 1.709 ± 0.007R _⊙ and 1.208 ± 0.006R _⊙, respectively. For the BX Dra contact system the masses are 2.19 ± 0.13M _⊙ and 0.63 ± 0.06M _⊙, and the radii, 2.13 ± 0.04R _⊙ and 1.26 ± 0.03R _⊙, for the primary and secondary, respectively. In both cases, the estimated luminosities seem to be slightly greater that the values derived from the Hipparcos distances.     

Observations and light curve solutions of a selection of middle-contact W UMa binaries

Photometric observations in Sloan g′and i′ bands of W UMa binaries NSVS 4340949,T-Dra0–00959,GSC 03950–00707,NSVS 4665041,NSVS 4803568,MM Peg,MM Com and NSVS4751449 are presented.The light curve solutions revealed that the components of each target are of G and K spectral types.The binaries of the sample have middle-contact configurations whose fillout factors are within the range 0.2–0.4.The only exception is NSVS 4751449 which is in deeper contact(fillout factor of 0.55).It precisely obeys the relation between mass ratio and fillout factor for deep,low mass ratio overcontact binaries.One of the eclipses of almost all targets(except MM Peg)is an occultation and their photometric mass ratios and solutions could be accepted with confidence.We found that the target components have almost equal temperatures but differ considerably in size and mass.The components of the partially-eclipsed MM Peg have close parameters.Our solutions reveal that NSVS 4340949,T-Dra0–00959,NSVS 4803568 and MM Com are of W subtype while GSC 03950–00707,NSVS 4665041,MM Peg and NSVS 4751449 are of A subtype.This subclassification is well-determined for all totallyeclipsed binaries.The targets confirm the trends in which W-subtype systems have smaller periods and lower temperatures than A subtype binaries.     

Application of the Kalman filter to light curves of eclipsing binaries

Recently Kopal (1975a, b, c, d) initiated a new approach to the analysis of the light curves of eclipsing binary systems in which the solution is based on transforming the problem from the conventional time-domain into the frequency-domain. Irrespective of the type of eclipse, the present formulation of the frequency approach requires that a set of quantitiesA _2m, called moments, be determined from the observations.It is the purpose of the present paper to describe a data interpolation and smoothing technique based on a version of the Kalman filter to pre-process observations and to determine the quantitiesA _2m in an optimal sense.     

Absolute physical parameters of three poorly studied detached eclipsing binaries

The photometric and spectroscopic data for three double-lined detached eclipsing binaries were collected from the photometric and spectral surveys.The light and radial velocity curves of each binary system were simultaneously analyzed using Wilson-Devinney(WD)code,and the absolute physical and orbital parameters of these binaries were derived.The masses of both components of ASASSN-V J063123.82+192341.9 were found to be M1=1.088±0.016 and M20.883±0.016 M⊙;those of ASAS J011416+0426.4 were determined to be M1=0.934±0.046 and M2=0.754±0.043 M⊙;and those of MW Aur were derived to be M1=2.052±0.196 and M21.939±0.193 M⊙.Finally,the evolutionary status of these detached binaries was discussed based on their absolute parameters and the theoretical stellar models.     

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.     

Light curve solutions of the eclipsing Kepler binaries KIC 5080652, KIC 5285607, KIC 9236858 and KIC 11975363

We carried out light curve solutions of four detached binaries with circular orbits, observed by Kepler. As a result their orbital inclinations, temperatures and relative stellar radii were determined. We estimated also their global parameters on the base of the obtained solutions and empirical relation “temperature, luminosity” for MS stars. The out-of-eclipse light curves of KIC 5080652, KIC 9236858 and KIC 11975363 reveal a trend the bigger amplitudes to correspond to single-waved shape while the two-waved shape to be inherent to the smaller amplitudes. This type of variability was attributed to gradually transition between state with two almost opposite cool spots and state with bigger in size polar spot. We detected also several microflares of KIC 11975363 with amplitudes of 0.002–0.003 mag.