UMa Binaries Research Articles

Light curve analysis and evolutionary status of four newly identified short-period eclipsing binaries

We present the physical and orbital parameters of four short-period eclipsing W UMa systems: ZTFJ000030.44+391106.9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ000030.44 +391106.9$$\\end{document} (referred to as S1), ZTFJ000817.08+402532.1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ000817.08+402532.1$$\\end{document} (referred to as S2), ZTFJ002158.44+252934.04\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ002158.44+252934.04$$\\end{document} (referred to as S3), and ZTFJ003357.62+415747.8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ZTFJ003357.62+415747.8$$\\end{document} (referred to as S4). The absolute parameters and evolutionary status of these systems are determined, and new times of minima are calculated. Additionally, we present the 3D fill-out configuration for each system. The four Systems exhibit moderate contact W UMa binary with a fill-out factor of 49%, 38%, 28%, and 51%, respectively. Comparing the systems’ periods, we observed a proportional relationship, where shorter periods correspond to lower fill-out factors, and longer periods were associated with higher fill-out factors. Based on the derived surface temperatures and mass ratios of the components, all systems are classified as A-type W UMa binaries. The obtained parameters in addition to a list of previously published data are then utilized to derive an updated Mass-Luminosity relation (M-L) for both A and W-type eclipsing W UMa systems. A comparison with previously published relations reveals that the majority of the EW systems lie between 0.2 and 2 Msun on the M-L diagram. Moreover, we discuss the dynamical evolutionary aspects and evolutionary status of the four components, along with their positions on the Zero Age Main Sequence (ZAMS) and Terminal Age Main Sequence (TAMS).

Period Investigation on Two W UMa Binaries HH UMa and V1175 Her

HH UMa and V1175 Her are two W UMa contact binary systems whose periods were reported as undergoing secular increase. In this paper, we improved their period analyses with a more extensive database of eclipse timings, finding that both periods show cyclic variation. The cyclic variation could be attributed to a Light Travel Time Effect induced by a third body. Both circular orbit and eccentric orbit cases were considered. For HH UMa, the cyclic variation with a period of around 20 yr has been detected, which may be caused by a third body with the mass larger than 0.23 M ⊙. However, no parabolic variation was detected in its O−C curve, implying the balance of the mass transfer between the two components and the angular momentum loss from the binary system. As to V1175 Her, a long-term period increase superposed on a periodic oscillation was detected. The period increase with a rate of about dP/dt = 2 × 10−7day yr−1 indicates the mass transfer from the less massive component to its companion. The cyclic variation of about 7.5 yr could be caused by a hierarchical third body with a minimal mass exceeding 0.46M ⊙ orbiting around the central binary. This mass is larger than that of the less massive component of the binary, which means that the secondary component was not replaced by the third body during early stellar interactions, implying that it keeps original dynamical information. By removing angular momentum from the central binary system, the tertiary component has played a significant role in the formation of contact binaries.

New Photometric Investigations of G-type Contact Binary TU Boo

Two sets of CCD photometric observations for contact binary TU Boo were obtained in 2020 and 2021. Different from its asymmetric light curves published from the literature, our BVR c I c -band curves show that the heights of maximum are almost equal. These distortions of light curves possibly indicate that the components were active in past 25 yr, but they were stable in the last two years. For total-eclipse binary TU Boo, due to some star-spots on the surface of the components, the physical structure obtained by many investigators are different. Therefore, the symmetric multi-color light curves in 2020, 2021 are important for understanding configuration and evolution of this system. By using the Wilson–Devinney program, it is confirmed that TU Boo is an A-type shallow-contact binary with the temperature difference of ΔT = 152 K and fill-out of f = 14.67%. In the O−C diagram of orbital period analysis, a cyclic oscillation superimposed on a continuous decrease was determined. The long-term decreasing is often explained by the mass transfer from the more massive star to less massive one, this system will evolve into a deeper contact binary with time. The cyclic oscillations computed from much more CCD times of light minimum maybe result from the light-travel time effect via the presence of a third body. These characters of structure, evolution and ternary belong to typical A-type W UMa binaries with spectral G.

Absolute parameters of four W UMa stars with extreme low mass ratios

Photometric observations of four extreme low mass ratio W UMa binaries with wide total eclipses, and their absolute parameters are presented. The main results are as follows: (i) ASAS J015429+2042.8 is of A subtype while V755 Cep, VESPA V22 and GSC 02800-01387 are of W subtype; (ii) The mass ratios are close to the lower mass-ratio limit and can be classified as Extreme Low Mass Ratio Binaries (ELMRB). (iii) The fill-out factors of ASAS J015429+2042.8 and VESPA V22 are 0.16 and 0.21 respectively, the one of GSC 02800-01387 is 0.63 while the one of V755 Cep is 0.83; (iv) The smaller in size (and less massive) components of all targets are located above the MS band of the evolutional diagrams while the bigger (and more massive) components are located around ZAMS; (v) Our ELMRB systems fall into the stability zone with Jspin/Jorb lower than the Darwin’s instability ∼1/3.

Absolute parameters of the three totally-eclipsing WUMa stars NSVS 2443858, NSVS 780649 and V1098 Her

We present the first photometric analysis of three totally-eclipsing W UMa binaries, NSVS 2443858, NSVS 780649 and V1098 Her. The absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve solutions. The results show that: (i) Two of the systems, NSVS 2443858 and V1098 Her, are of A subtype while the obtained temperature of the secondary component of NSVS 780649 indicates that it is a W-subtype system; (ii) The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary (EMRB) systems; (iii) All the systems have deep contact configurations, so they also are deep low mass ratio (DLMR) systems; (iv) The components of our systems are stars of F and G spectral type and undergo total eclipses; (v) The sum 0.871 M ⊙ of the component masses of NSVS 780649 is below the mass limit of 1.0-1.2 M ⊙ assumed for the known contact binary stars.

Statistics of 700 Individually Studied W UMa Stars

Abstract We present a statistical study of the largest bibliographic compilation of stellar and orbital parameters of W UMa stars derived by light-curve synthesis with Roche models. The compilation includes nearly 700 individually investigated objects from over 450 distinct publications. Almost 70% of this sample is comprised of stars observed in the past decade that have not been considered in previous statistical studies. We estimate the ages of the cataloged stars, model the distributions of their periods, mass ratios, temperatures, and other quantities, and compare them with the data from the Catalina Real-Time Transient Survey, LAMOST, and Gaia archives. As only a small fraction of the sample has radial-velocity curves, we examine the reliability of the photometric mass ratios in totally and partially eclipsing systems and find that totally eclipsing W UMa stars with photometric mass ratios have the same parameter distributions as those with spectroscopic mass ratios. Most of the stars with reliable parameters have mass ratios below 0.5 and orbital periods shorter than 0.5 days. Stars with longer periods and temperatures above 7000 K stand out as outliers and should not be labeled W UMa binaries. The collected data are available as an online database at https://wumacat.aob.rs.

Photometric and Spectroscopic Analysis of Four Contact Binaries

Abstract We present the photometric and spectroscopic analysis of four W UMa binaries J015829.5+260333 (hereinafter as J0158), J030505.1+293443 (hereinafter as J0305), J102211.7+310022 (hereinafter as J1022), and KW Psc. The VR c I c band photometric observations are carried out with the 1.3 m Devasthal Fast Optical Telescope (DFOT). For low-resolution spectroscopy, we used the 2 m Himalayan Chandra Telescope (HCT) as well as the archival data from the 4 m LAMOST survey. The systems J0158 and J0305 show a period increase rate of 5.26( ± 1.72) × 10−7 days yr−1 and 1.78( ± 1.52) × 10−6 days yr−1, respectively. The period of J1022 is found to be decreasing with a rate of 4.22 ( ± 1.67) × 10−6 days yr−1. The period analysis of KW Psc displays no change in its period. The PHOEBE package is used for the light-curve modeling and basic parameters are evaluated with the help of the GAIA parallax. The asymmetry of light curves is explained with the assumption of cool spots at specific positions on one of the components of the system. On the basis of temperatures, mass ratios, fill-out factors, and periods, the system J1022 is identified as a W-subtype system while the others show some mixed properties. To probe the chromospheric activities in these W UMa binaries, their spectra are compared with the known inactive stars’ spectra. The comparison shows emission in H α , H β , and Ca II. To understand the evolutionary status of these systems, the components are plotted in mass–radius and mass–luminosity planes with other well characterized binary systems. The secondary components of all the systems are away from ZAMS, which indicates that the secondary is more evolved than the primary component.

Light curve analysis of six totally eclipsing W UMa binaries

Abstract We analyze multicolor light curves of six totally eclipsing, short-period W UMa binaries and derive, for the first time, their orbital and stellar parameters. The mass ratios are established robustly through an automated q-search procedure that performs an heuristic survey of the parameter space. Five stars belong to the W and one to the A subtype. The mass ratios range from 0.23 to 0.51 and the fillouts from $10\%$ to $15\%$. We estimate the ages and discuss the evolutionary status of these objects in comparison with a sample of other short-period W UMa binaries from the literature.

Magnetic Activity and Period Variation Studies of the Four W Uma-type Eclipsing Binaries: UV Lyn, V781 Tau, NSVS 4484038, and 2MASS J15471055+5302107

Abstract We present new photometric data and LAMOST spectra for the W UMa binaries UV Lyn, V781 Tau, NSVS 4484038, and 2MASS J15471055+5302107. The orbital and starspot parameters are obtained using the Wilson–Devinney program. Comparing the starspot parameters at different times, there are magnetic activities in these four binaries. The orbital period of UV Lyn is increasing at a rate of dP/dt = +8.9(5) × 10−8 days yr−1, which maybe due to mass transfer from the less massive component to the more massive component (dM 1/dt = −6.4 × 10−8 M ⊙ yr−1). The period variation of 2MASS J15471055+5302107 is also increasing at a rate of 6.0(4) × 10−7 days yr−1, which can be explained by mass transfer from the less massive component to the more massive component (dM 1/dt = −2.8 × 10−7 M ⊙ yr−1). The period variation of V781 Tau presents the downward parabola superimposed the cyclic oscillation. The period of V781 Tau is decreasing (dP/dt = −3.2(4) × 10−8 days yr−1), which can be explained by mass transfer from the more massive component to the less massive component (dM 2/dt = −2.2 × 10−8 M ⊙ yr−1). The cyclic oscillation may be due to the magnetic activity with a period of 30.8(5) yr rather than a third body. The period variation of NSVS 4484038 also shows the cyclic oscillation, which could be explained by the magnetic activity with 10.8(1) yr or a black hole candidate. Interestingly, there is a depth variation between the light minimum times of NSVS 4484038, which may also be caused by stellar magnetic activity.

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

Photometric BVRc 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.

Global parameters of the W UMa stars FI Lyn, UV Lyn, and NSVS 781878

AbstractPhotometric and spectral observations of the W UMa binaries FI Lyn, UV Lyn, and NSVS 781878 with periods of around 9.5–10 hr were carried out in order to determine their global parameters by simultaneous light curve and radial velocity curve solutions. We found that the three targets have shallow‐contact configurations with close in mass and radius components. UV Lyn is of W‐subtype, NSVS 781878 is of A‐subtype, while FI Lyn may be considered as binary in thermal contact. Our data show evidences of photospheric activity of the targets but not of emission in the Hα line. The surface inhomogeneity of UV Lyn is stable during the last several decades. Its O–C diagram implies presence of third body with a period of 24 years. The distances of FI Lyn, UV Lyn, and NSVS 781878 calculated from the derived luminosities coincide with those obtained by GAIA astrometrically.

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.

Case AD, AR, and AS binary evolution and their possible connections with W UMa binaries

ABSTRACT Close detached binaries were theoretically predicted to evolve into contact by three subtypes of case A binary evolution, cases AD, AR, and AS, which correspond to the formation of contact during dynamic-, thermal-, and nuclear-time-scale mass transfer phases, respectively. It is unclear, however, what is the difference between contact binaries in these subtypes, and whether all of these subtypes can account for the formation of observed W Ursae Majoris (W UMa) binaries. Using Eggleton’s stellar evolution code with the non-conservative assumption, I obtained the low-mass contact binaries produced by cases AD, AR, and AS at the moment of contact and their parameter spaces. The results support that the progenitors of low-mass contact binaries are detached binaries with orbital periods shorter than $\sim 2\!-\!5\,$ d, and their borderlines depend strongly on the primary mass. In addition, the period–colour relations for cases AR and AS can be in better agreement with that for observed W UMa candidates, but case AD shows a significantly worse agreement. Moreover, cases AR and AS can produce a short-period limit (corresponding to a low-mass limit) at almost any age, e.g. from young age ($\sim 0.2\,$ Gyr) to old age ($\sim 13\,$ Gyr), agreeing with observed W UMa binaries in star clusters, but no such limit occurs for case AD at any age. These results support that cases AR and AS, as opposed to case AD, can lead to W UMa binaries (including young W UMa binaries).

Global Parameters of 12 Totally Eclipsing W UMa Stars

Abstract Photometric observations of 12 totally eclipsing W UMa binaries (NSVS 3325547, V646 Lac, V1320 Cas, V539 Dra, V816 Cep, NSVS 9045055, V1115 Cas, V902 Cep, V596 Peg, NSVS 1768818, V619 Peg, and NSVS 3198272) are presented. We found that the longer (in phase units) the flat eclipses are, the smaller the mass ratios (or the reciprocal values) are. The mass ratios of five targets turned out close to the lower-mass ratio limit. We found that the periods of V1115 Cas and V646 Lac increase, while that of V596 Peg decreases. Masses, radii, and luminosities of the target components were calculated by the light-curve solutions and Gaia distances. In order to perform more reliable statistical analysis of the results we added to the sample of 12 targets from this paper another 29 totally eclipsing W UMa stars studied by us earlier. As a result we found the following trends: (a) the radius and luminosity of the target components increase with their mass but the dependencies are different from those of main-sequence (MS) stars; (b) the temperatures of stellar components whose masses are above 1 M ⊙ tend to be lower than those of the corresponding MS stars, while the temperatures of stellar components whose masses are below 1 M ⊙ tend to be higher than those of the corresponding MS stars; (c) there is no relationship between the fillout factor and mass ratio; and (d) 11 of the 41 targets are of A subtype, 24 are of W subtype, and 6 systems are with equal-temperature components.

OT UMa and GU leo: Two middle-contact w UMa binaries with similar stellar components

We present photometric observations of the W UMa binaries OT UMa and UG Leo. Our results from the light curve solutions are: (i) The two targets show partial eclipses; (ii) The components OT UMa and UG Leo are of G spectral type; (iii) Detailed q-search analysis was carried out for determination of the mass ratios; (iv) The two binaries are of W subtype with middle fillout factors. We estimated masses, radii and luminosities of the target components by our light curve solutions and using GAIAdistances. It turned out that their values are similar for the two targets. The paper presents a discussion on the determination of the temperatures and mass ratios of partially-eclipsing W UMa stars.

BVRCIC Observations, Analysis, and Spectra of The Most Extreme Mass Ratio (Totally Eclipsing) W UMa Binary, V1187 Herculis

CCD, BVRI primary light curves of V1187 Her were taken in 2017 May and 2018 May at the Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University. A spectrum was taken earlier at Dominion Astrophysical Observatory (DAO) with the 1.8 m telescope. The spectral type is F(8.5 ± 1)V, resulting in a surface temperature of 6250 ± 125 K (Cox ), so solar-type activity is expected. V1187 Her was previously identified as a low-amplitude, short-period, over-contact eclipsing binary (EW) with an orbital period of 0.310726 d. Strikingly, despite its low amplitude (∼0.15 mag), the early light curves show a total eclipse (eclipse duration: 31.5 minutes). This can only occur (in the absence of a strong third light) if the binary is an exceptionally extreme mass ratio binary, perhaps the most extreme known. Eight instances of minimum light were calculated. A 12-year period study reveals a secular period decrease in the orbital period with good confidence. The rate of period change is dP/dt = −1.5 × 10−07 d/yr, probably due to magnetic braking. Its Roche Lobe fill-out is found to be a hefty 84% along with a mass ratio of only ∼0.044; indeed, the most extreme known among solar-type (i.e., W UMa) binaries. It has a cool spot region. The secondary component has a temperature of K, which makes it a W-subtype binary (the less massive component is hotter). The inclination is only ∼67° despite its total eclipses. A q-search was conducted, which showed the 0.044 value was the best fit to the light curves. Additionally, follow-up observations were taken on 2018 May 4, which confirmed the mass ratio found from the earlier curves.

Photometric and Spectral Observations of the W UMa Stars NSVS 4161544 and 1SWASP J034501.24+493659.9. GAIA Challenges

Abstract Photometric and spectral observations of the W UMa binaries NSVS 4161544 and 1SWASP J034501.24+493659.9 with periods of around 8 hr are presented. The simultaneous light-curve and radial-velocity-curve solutions revealed that the two targets have over-contact configurations, and their components undergo partial eclipses. The derived parameters of NSVS 4161544 are: mass ratio q = 3.377, orbital inclination i = 65.00, temperatures T 1 = 6016 K and T 2 = 5726 K, masses M 1 = 0.43 and M 2 = 1.47 radii R 1 = 0.74 and R 2 = 1.28 luminosities L 1 = 0.64 and L 2 = 1.51 . The derived parameters of 1SWASP J034501.24+493659.9 are: mass ratio q = 2.378, orbital inclination i = 60.30, temperatures T 1 = 6514 K and T 2 = 6494 K, masses M 1 = 0.275 and M 2 = 0.654 radii R 1 = 0.693 and R 2 = 1.012 luminosities L 1 = 0.775 and L 2 = 1.632 . Hence, the masses of the 1SWASP J034501.24+493659.9 components are quite small for the rest global parameters, and their sum of 0.93 is slightly below the lower mass limit of 1.0–1.2 M ⊙ for the contact binaries. The calculated distance of NSVS 4161544 almost coincides with that determined by GAIA. The calculated distance of 1SWASP J034501.24+493659.9 is considerably smaller than the GAIA value that is most likely due to overestimation of the interstellar extinction to this star from the Galactic disk.

The W UMa binaries USNO-A2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac: light curve solutions and global parameters based on Gaia distances

We present photometric observations in Sloan filters g′, i′ of the eclipsing W UMa stars USNO-A2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac. The sinusoidal-like O – C diagram of V471 Cas indicates the presence of a third body with mass 0.12 M⊙ (a red dwarf) at distance 897 R⊙. The O – C diagram of V479 Lac reveals a period decrease of dP/dt = –1.69 × 10−6 d yr−1. The results of the light curve solutions are: (i) the targets are overcontact binaries with small fill-out factors; (ii) their components are F–K stars, comparable in size, whose temperature differences are below 80K; (iii) all targets undergo partial eclipses and to limit the possible mass ratios we carried out two-step q-search analysis. The target global parameters (luminosities, radii, masses) were obtained on the basis of their Gaia distances and the results of our light curve solutions. The obtained total mass of V560 Lac turns out to be smaller than the lower mass limit for presently known W UMa binaries of 1.0 – 1.2 M⊙, i.e. this target is a peculiar overcontact system.

Variable stars in M37

The CCD photometric observations of open star cluster M37 (NGC 2099) were carried out up to a limiting magnitude of V ∼ 20 in both B and V filters to search for variable stars using a 2k × 4k CCD and the 1.3 m telescope at the Vainu Bapu Observatory, Kavalur. A total of 314 stars were in the first observing run, out of which 60 were identified as variables. Eight out of the identified 60 variables are classified as W UMa binary stars. For model fitting, we used PHOEBE based on the W-D code to estimate the physical parameters of these newly detected W UMa binaries that theoretically best match the observed light curves.

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.