Long-term Period Decrease Research Articles

Spectroscopic and photometric investigations of the totally eclipsing contact binary V1320 Cas

We analyzed the light curve of the total eclipse contact binary V1320 Cas, obtained reliable photometric solutions, confirmed it to be a W-type contact binary with a mass ratio of 3.404 and a contact degree of 23.9%, a cool spot is discovered on the less massive component. Orbital period analysis indicates that the period of V1320 Cas is decreasing at a rate of dPdt=1.78×10−7 day yr−1, superimposed with a cyclic modulation with a period of 1.425 yr, long-term period decrease may be caused by the combination of mass transfer and angular momentum loss, and the cyclic modulation may be caused by the third companion. Using the photometric solutions and Gaia distance, we calculated the absolute physical parameters and plotted mass-luminosity and mass–radius diagrams to analyze the evolutionary status of V1320 Cas, the more massive component is a main sequence star, while the less massive component has higher luminosity and radius than those of main sequence stars with the same mass. With the decreasing orbital period, the two components of V1320 Cas will be gradually closer, while the binary may evolve toward deep contact.

A Study of Ten Early-type Contact Binary Stars in the Small Magellanic Cloud

To study early-type binary systems in different evolutionary stages or environments, the Small Magellanic Cloud (SMC) is an ideal laboratory due to its low metallicity compared to that of the Milky Way. We conduct a study on the period changes of the close binary systems with B-type spectral classifications in the SMC using OGLE collections. Ten B-type binaries that show no significant periodic variations based on the current observational data were analyzed. Through O − C analysis, four of the ten early-type binaries show a long-term period decrease, one shows a long-term period increase, and the other five systems are ambiguous due to the limitations of the observational data. Among the period-decreasing systems, two may be mainly caused by mass transfer, while the rest may be caused by angular momentum loss. The Wilson-Devinney code (W-D method) is used to analyze their I-band photometric light curves. According to the W-D results, five early-type binaries are in the deep contact state, three are in the shallow contact state, while two are in the medium contact state, and the temperature ratios of these early-type binaries are all close to unity. The five deep contact binaries are highly unstable systems and therefore serve as important objects for the study of binary mergers. Finally, a discussion on the evolution of early-type binary stars is conducted by combining the analyses of the light curves and the periodic changes of ten early-type binaries, that implies that the majority of early-type binaries in the SMC may form contact binaries from a phase of rapid mass transfer.

The First Photometric and Spectroscopic Studies of ASASSN-V J015428.67+204247.2 and its Relation to the Population of Low Mass Ratio Contact Binaries

We performed photometric, spectroscopic and orbital period investigations of ASASSN-V J015428.67+204247.2 (hereafter, J015428) for the first time. The light curves of VRI bands were obtained. Through the analysis of Wilson–Devinney program, J015428 was found as an A-subtype medium contact binary system with a low-mass ratio (q = 0.129, f = 26.8%). The atmospheric parameters were determined in spectroscopic analysis. In the orbital period investigations, we found that the orbital period of J015428 decreases at the rate of −7.13 × 10−8 day yr−1. And the long-term orbital period decrease is possibly due to angular momentum loss (AML). The absolute parameters was calculated with the photometric solutions and Gaia distance. Through the analyses of mass–radius and mass–luminosity diagrams of 54 contact binaries with the low mass ratios (0.096 ≤ q ≤ 0.15), the evolutionary states of low mass ratio binaries were investigated. The results by analyzing the energy transfer parameter indicated that energy transfer rate was a function of mass and bolometric luminosity ratio. We estimated the initial masses and the densities of two components and the age of the binary. The analysis of the orbital angular momentum supposed that J015428 may evolved from a short-period detached binary by AML. J015428 is in a stable contact stage at present.

V2769 Orionis: A new low-mass-ratio and deep-contact binary

We carried out the first multi-color light curves analysis of the eclipsing binary V2769 Ori. The photometric solution was determined by applying the Wilson–Devinney method. The results show that V2769 Ori is a deep, low-mass-ratio contact binary with a mass ratio of q=0.162(±0.003) and a contact degree of f=55(±8)%. The total eclipse characteristics of V2769 Ori imply that the photometric solution we obtained is reliable. With all available light minimum times, the O–C diagram was constructed and analyzed. The orbital period analysis reveals a long-term period decrease at a rate of dP/dt=−1.24(±0.08)×10−6dyr−1 and a periodic oscillation with a period of 8.77(±0.15) years. The secular period decrease can be explained by a combination of mass transfer between the two components and the angular momentum loss of the system. As the orbital period decrease, the shrinking of the inner and outer critical Roche lobes causes an increase in contact degree, and the binary system will finally merge into a rapidly rotating single star. Periodic oscillation may be the result of the light-travel time effect due to the presence of an unseen component.

A Single-lined Spectroscopic Binary Companion to an Active and Deep Contact Binary in a Quintuple Stellar System

Abstract V410 Aur is a known deep and low-mass-ratio contact binary with a spectroscopically tertiary component and a visual companion. However, the physical and orbital properties of the tertiary are unknown. We constructed (O − C) curve with 117 new eclipse times and those collected from the literature, which shows a cyclical variation with a period of 25.44 (±1.17) yr and a projected semimajor axis of 0.0348 (±0.0021) days while it undergoes a long-term period decrease at a rate of dP/dt = −1.58 × 10−7daysyr−1. The cyclical variation is analyzed for the light-travel time effect. The minimum mass of the third body is determined as 1.39 (±0.13) M ⊙ that is much larger than the inferred value (0.97 M ⊙) of spectroscopic investigation, which indicates that the spectroscopically tertiary is a single-lined spectroscopic binary with an unseen component. The maximum orbital semimajor axis 6.19 (±0.67) au of the third body is determined. Gaia detected a visual companion to V410 Aur at practically the same distance from the Sun nicely confirming the physical bond. These results reveal that V410 Aur contains a single-lined spectroscopic binary with a visual companion in a quintuple stellar system. TESS photometric solutions confirmed that V410 Aur is a deep overcontact binary with a fill-out factor of 73.83(88)% where the additional light contribution is about 24.80(18)%. The continuous variations of light curves are explained by the evolution of a dark spot on the more massive component. The parabolic variation in the (O − C) curve may be caused by the mass transfer from the massive component to the less massive one in the deep overcontact binary.

V0644 Ser: An Active Ultrashort Period Contact Binary Star

The photometric solutions of the ultrashort period close binary V0644 Ser based on our new complete BVRI light curves are derived by the Wilson–Devininney code. The results show that V0644 Ser is a W-type shallow contact binary, and the third light was found in the R and I bands. Compared with the light curves in 2011, the amplitude variation of the secondary maximum can be explained by the temperature change from hot to cold in the local region of the star surface caused by magnetic activity or convective instability. Combined with the Gaia parallax, the absolute parameters of this system are obtained: M 1 = 0.29(4) M ⊙, M 2 = 0.56(9) M ⊙, R 1 = 0.48(3) R ⊙, R 2 = 0.65(3) R ⊙, L 1 = 0.11(2) L ⊙, L 2 = 0.16(2) L ⊙. To study the period variation, we fitted the SuperWASP, CSS, ASAS-SN and ZTF survey timing data to obtain light minima times spanning 14 yr. Through O − C analysis, we find that the orbital period of this system has a long-term period decrease and periodic oscillation. The long-term period decrease can be explained by the mass transfer from more-massive component to less one and angular momentum loss via magnetic stellar wind. With the period decrease, this system is evolving from the present shallow contact phase to a relatively deeper stage predicted by the thermal relaxation oscillation theory. Periodic oscillation can be explained by the light-time effect of the cool third body. This third body may play an important role in the early formation and evolution of the binary system by removing angular momentum.

BM UMa: A middle shallow contact binary at pre-transition stage of evolution from W-type to A-type

Abstract In this study, all unpublished time series photometric data of BM UMa (q ∼ 2.0, P = 0.2712 d) from available archives were re-investigated together with new data taken from the 2.4-m Thai National Telescope of the Thai National Observatory. Based on period analysis, there is a short-term variation superimposed on the long-term period decrease. The trend of period change can be fitted with a downward parabolic curve indicating a period decrease at a rate of dP/dt = −3.36(±0.02) × 10−8 d yr−1. This long-term period decrease can be explained by mass transfer from the more massive component (M2 ∼ 0.79M⊙) to the less-massive one (M1 ∼ 0.39M⊙), in combination with angular momentum loss. For photometric study, we found that the binary consists of K0 V stars and at the intermediate shallow of contact configuration with evolution of fill-out factor from 8.8% (in 2007) to 23.2% (in 2020). Those results suggest that the binary is at the pre-transition stage of evolution from W-type to A-type, agreeing with the results of statistical study of W-type contact binaries. The mass of M2 will be decreased close to or below M1 and the mass ratio will be decreased (q < 1.0). In this way, the binary will evolve into an A-type as a deeper normal over-contact system with period increase. Finally, the binary will become a merger or a rapid-rotating single star when the mass ratio meets the critical value (q < 0.094), and produce a red nova.

Photometric Study and Absolute Parameter Estimation of Six Totally Eclipsing Contact Binaries

Abstract High precision CCD observations of six totally eclipsing contact binaries were presented and analyzed. It is found that only one target is an A-type contact binary (V429 Cam), while the others are W-type contact ones. By analyzing the times of light minima, we discovered that two of them exhibit secular period increase while three manifest long-term period decrease. For V1033 Her, a cyclic variation superimposed on the long-term increase was discovered. By comparing the Gaia distances with those calculated by the absolute parameters of 173 contact binaries, we found that the Gaia distance can be applied to estimate the absolute parameters for most contact binaries. The absolute parameters of our six targets were estimated using their Gaia distances. The evolutionary status of contact binaries was studied, and we found that the A- and W-subtype contact binaries may have different formation channels. The relationship between the spectroscopic and photometric mass ratios for 101 contact binaries was presented. It was discovered that the photometric mass ratios are in good agreement with the spectroscopic ones for almost all of the totally eclipsing systems, which is corresponding to the results derived by Pribulla et al. and Terrell & Wilson.

The first photometric investigations of the G-type shallow contact binary IO Cnc

IO Cnc was classified to be a new G-type (G0) W UMa-type eclipsing binary system. Our first multicolor photometric solutions show that IO Cnc is a new W-subtype shallow contact binary with a fill-out factor of f = 16.1% and a low mass ratio of q = 3.12 (or 1/q = 0.32). During orbital period investigations, a cyclic variation and a downward parabolic variation with a rate of (−1.28 ± 0.43) × 10−7 d yr−1 was discovered in the observed–calculated (O − C) curve. The cyclic variation was analyzed by the light travel time effect (LTTE) via a potential red dwarf companion star, an orbital semi-major axis shorter than 4.88 ± 0.82 AU was obtained. Finally, we collect physical parameters of a sample of 50 G-type shallow contact binaries (f ≤ 20%), it is suggested that most of the G-type shallow contact binaries are undergoing a long-term and periodic orbital period changes, especially more systems show long-term decreases. The long-term orbital period decrease indicates that IO Cnc is in a mass transferring from the more massive component to the less massive one. With the long-term decrease of the orbital period, this shallow contact binary will evolve into a deeper contact one.

Photometric investigations on two totally eclipsing contact binaries: V342 UMa and V509 Cam

By analyzing two sets of complete BVRcIc light curves for V342 UMa and three sets of complete BVRcIc light curves for V509 Cam, we determined that the two systems are both W-subtype contact binaries and that V342 UMa manifests a shallow contact configuration, while V509 Cam exhibits a medium contact configuration. Given that both of them are totally eclipsing binaries, the physical parameters derived only by the photometric light curves are reliable. Meanwhile, the period changes of the two targets were analyzed based on all available eclipsing times. We discovered that V342 UMa shows long-term period decrease with a rate of −1.02(± 0.54) × 10−7 d yr−1 and that V509 Cam displays long-term period increase with a rate of 3.96(± 0.90) × 10−8 d yr−1. Both the conservative mass transfer and angular momentum loss via magnetic stellar winds can be used to interpret the long-term period decrease of V342 UMa. The long-term period increase of V509 Cam can be explained by mass transfer from the less massive star to the more massive one. The absolute parameters of the two binaries were estimated according to their Gaia distances and our derived photometric solution results. This method can be extended to other contact binaries without radial velocities but with reliable photometric solutions. Their evolutionary states were investigated and we found that they reveal properties that are identical to other W-subtype contact systems.

YZ Phoenicis: a very short period K-type contact binary with variation of the O’Connell effect and orbital period change

Abstract YZ Phe is a very short-period contact binary (Sp. = K2 V) with an orbital period of 0.2347 d near the short period limit (0.22 d). We present the complete light curves which photometric data were obtained from the 60 cm telescope of PROMPT-8 at CTIO in Chile during 2016 June to October and 2017 August. The photometric solutions were determined by using the Wilson & Devinney code and the results reveal that YZ Phe is a W-subtype shallow contact binary ($f\sim 10\,$, q = 2.635, or 1/q = 0.379 for W subtype) with rotational motion of a large hot spot on the more massive component, showing a strong O’Connell effect with variation of maxima in photometric time series at period of 4.20 yr and stellar cycle at period of 1.28 yr. By compiling all available eclipse times, the result shows a long-term period decrease at a rate of dP/dt = −2.64(±0.02) × 10−8 d yr−1, superimposed on a cyclic variation (A3 = 0.0081 d and P3 = 40.76 yr). This variation cannot be explained by the Applegate mechanism. Thus, the cyclic change may be interpreted as the light-travel time effect via the presence of a cool third body. Based on photometric solutions, the third light was detected as $2\,$ of the total light in V and I bands. These results support the existence of a third body. The long-term period decrease can be explained by mass transfer from the more massive component ($M_2 \sim 0.74\, M_{\odot }$) to the less massive one ($M_1 \sim 0.28\, M_{\odot }$) or plus angular momentum loss (AML) via magnetic braking. With 1/q < 0.4 and long-term period decrease, all factors suggest that YZ Phe is on the AML-controlled state and its fill-out factor will increase, as well as the system evolving into a deeper normal contact binary.

Physical Properties of the Close-in Tertiary in the Southern Triple-lined System VZ Lib

Abstract VZ Lib is a southern triple-lined system. By analyzing all available times of light minima, orbital period changes are revisited in detail. We discovered that the observed–calculated (O − C) curve shows a long-term period decrease at a rate of , revealing a mass transfer from the more massive component to the less massive one. A cyclic variation covering more than three cycles was discovered, which was analyzed for the light-travel-time effect via the presence of the tertiary companion. The cyclic variation has a short period of 2.96 (±0.04) yr and a small semiamplitude of 0.0039 (±0.0004) days. The mass of the third body was determined to be M ⊙ and an orbital semimajor axis shorter than au was obtained. Orbital properties of this close-in companion should provide valuable information on the formation of close binaries and stellar dynamical interaction. New complete light curves of VZ Lib were obtained and modeled with the Wilson–Devinney code. The light curves show a small but significant O’Connell effect that was not detectable in 1981 and 2007 but in 2004, so we derived a new photometric solution with assuming spot and a third light in the system. It is found that the light-curve subtype changed from A-type to W-type, which was possibly caused by a dark spot on the massive component. Our photometric solutions are in agreement with the spectroscopic results given by previous authors.

New photometric investigation of the low-mass-ratio contact binary star V1853 Orionis

Four-color charge-coupled device (CCD) light curves in the B, V, Rc and Ic bands of the total-eclipsing binary system V1853 Orionis (V1853 Ori) are presented. By comparing our light curves with those published by previous investigators, it is determined that the O’Connell effect on the light curves has disappeared. By analyzing those multi-color light curves with the Wilson-Devinney code (W-D code), it is discovered that V1853 Ori is an A-type intermediate-contact binary with a degree of contact factor of f = 33.3%(3.7%) and a mass ratio of q = 0.1896(0.0013). Combining our 10 newly determined times of light minima together with others published in the literature, the period changes of the system are investigated. We found that the general trend of the observed minus calculated (O – C) curve shows a downward parabolic variation that corresponds to a long-term decrease in the orbital period with a rate of dP/dt = −1.96(0.46) × 10−7 d yr−1. The long-term period decrease could be explained by mass transfer from the more-massive component to the less-massive one. By combining our photometric solutions with data from Gaia DR2, absolute parameters were derived as M1 = 1.20 M⊙, M2 = 0.23 M⊙, R1 = 1.36 R⊙ and R2 = 0.66 R⊙. The long-term period decrease and intermediate-contact configuration suggest that V1853 Ori will evolve into a high fill-out overcontact binary.

The first photometric investigation and period study of two W UMa-type binary systems: EF CVn and EH CVn

Abstract By analyzing the V, Rc, and Ic light curves of the two neglected W UMa-type binaries EF CVn and EH CVn using the Wilson–Devinney code, we have discovered that EF CVn is a median contact binary while EH CVn is a shallow contact binary, and they are both W-subtype binary systems. The mass ratio and fillout factor of EF CVn are q = 3.493 ± 0.063 and f = 32.0% ± 12.9%, respectively. Those of EH CVn are q = 3.331 ± 0.052 and f = 19.2% ± 10.9%, respectively. The addition of a dark spot on the secondary star is used to interpret the asymmetric light curves of EF CVn. An orbital period analysis of EF CVn indicates that there is a cyclic oscillation with an amplitude of 0.0064 d and a period of 15.65 yr, accompanied by a continuous increase at a rate of dp/dt = 4.52 × 10−7 d yr−1. The periodic oscillation can reasonably be explained by the light travel-time effect of an additional component. The secular increase is probably generated by conservative mass transfer from the primary star to the secondary star. Meanwhile, an analysis of the orbital period of EH CVn was also performed. A long-term period decrease at a rate of dp/dt = −5.20 × 10−8 d yr−1 was discovered; this is possibly interpreted as caused by mass transfer from the more massive component to the less massive component.

Magnetic Activity and Period Variation Studies of the Short-period Eclipsing Binaries. II. V1101 Her, AD Phe, and NSV 455 (J011636.15–394955.7)

In this paper, we present new BVRI light curves of short-period contact eclipsing binaries V1101 Her and AD Phe from our observations carried out from 2014 to 2015 using the SARA KP and SARA CT telescopes. There is an eclipsing binary located at α(2000) = 01h16m3615 and δ(2000) = −39°49'557 in the field of view of AD Phe. We derived an updated ephemeris and found there a cyclic variation overlaying a continuous period increase (V1101 Her) and decrease (AD Phe). This kind of cyclic variation may be attributed to the light time effect via the presence of the third body or magnetic activity cycle. The orbital period increase suggests that V1101 Her is undergoing a mass-transfer from the primary to the secondary component (dM1/dt = 2.64(±0.11) × 10−6 M⊙ yr−1) with the third body (P3 = 13.9(±1.9) years), or 2.81(±0.07) × 10−6 M⊙ yr−1 for an increase andmagnetic cycle (12.4(±0.5) years). The long-term period decrease suggests that AD Phe is undergoing a mass-transfer from the secondary component to the primary component at a rate of −8.04(±0.09) × 10−8 M⊙ yr−1 for a period decrease and the third body (P3 = 56.2(±0.8) years), or −7.11(±0.04) × 10−8 M⊙ yr−1 for a decrease and magnetic cycle (50.3(±0.5) years). We determined their orbital and geometrical parameters. For AD Phe, we simultaneously analyzed our BVRI light curves and the spectroscopic observations obtained by Duerbeck & Rucinski. The spectral type of V1101 Her was classified as G0 ± 2V by LAMOST stellar spectra survey. The asymmetry of the R-band light curve of AD Phe obtained by McFarlane & Hilditch in 1987 is explained by a cool spot on the primary component.

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= −3.0×10−7d/yr, corresponding to a time scale 8.6×105yr. 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.

Period studies and photometric models for two EB-type binaries EU Hya and AW Vul

New photometry for two Algol-type binaries, EU Hya (P = 0.7782 d) and AW Vul (P = 0.8065 d), was carried out using the 60-cm telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, photometric elements were derived from the multi-color light curves. The modeled results indicate that the two systems are near-contact binaries, whose secondary components fill their Roche lobes. The fill-out factors of the primaries are fp = 81.2 (±0.2)% for EU Hya and fp = 82.4 (±0.3)% for AW Vul. Period analysis implies that there exists a downward parabola with a light-time orbit from the (O – C) curve. This kind of periodic oscillation may be attributed to the light-time orbit effect of a third companion. The long-term period decrease may be caused by mass and angular momentum loss. When the orbital period decreases, the fill-out factor of fp will increase. Our results indicate that the primaries will also eventually fill their Roche lobes. EU Hya and AW Vul may possibly evolve from semi-detached binaries into contact ones.

OO Aquilae: a solar-type contact binary with intrinsic light curve changes

New multi-color photometry of the solar-type contact binary OO Aql was obtained in 2012 and 2013, using the 60 cm telescope at Xinglong Station of the National Astronomical Observatories, Chinese Academy of Sciences. From two sets of light curves LC1 and LC2, photometric models were performed by using the 2003 version of the Wilson-Devinney code. The overcontact factor of the binary system was determined to be f = 37.0(±0.5)%. The intrinsic variability of this binary occurs in light maxima and minima, which could result from a possible third component and magnetic activity of the late type components. Based on all available light minimum times, the orbital period may change in a complicated mode, i.e., sudden period jumps or continuous period variations. The period of OO Aql may possibly undergo a secular period decrease with a rate of dP/dt = −3.63(±0.30) × 10−8 d yr−1, superimposed by two possible cyclic variations in the O – C curve. The long-term period decrease may be interpreted as conserved mass transfer from the more massive component to the less massive one. The 21.5-yr oscillation may be attributed to cyclic magnetic activity, and the 69.3-yr one may result from the light-time effect of an unseen tertiary body.

Period change investigation of the low mass ratio contact binary BO Ari

A photometric study and period change analysis for the A-type low mass ratio contact binary BO Ari is presented. The BVR light curves were fitted by using the Wilson–Devinney method. The photometric solution yields a low mass ratio of q = 0.1754(±0.0016) with a contact degree of f = 27.72%(±2.37%). We found a long-term orbital period decrease at a rate of dPdt=−3.49×10−7 d yr−1. This result indicates that the system is undergoing mass transfer from the primary component to the secondary with a mass transfer rate of m˙1m1 = −7.77×10−8 yr−1. With the period decrease, the inner and outer critical Roche surfaces will tighten and cause the degree of contact to increase. Therefore, BO Ari may evolve into a deeper contact system.

Starspot activity and period change in RT CrB

Abstract The light curves of RT CrB in the B and V bands observed by İbanoğlu et al. (1985, Ap&SS, 112, 133), and in the V band and the radial velocity curves observed by Sabby and Lacy (2003, AJ, 125, 1448), are analyzed using the Wilson–Devinney code. The results show that the distortions in the light curve observed by Sabby and Lacy (2003) can be fitted by two spots, a hot spot on the primary component and a cool spot on the secondary star. The temperature ratios of the spotted region to the photosphere, Ts/Tph, are 1.181(±0.053) and 0.803(±0.057) respectively. Combining the radial velocity curves with the light curves, our analysis gives reliable, accurate estimates of the physical parameters of the system, M1 = 1.35(±0.01)M⊙ and R1 = 2.88(±0.05)R⊙ for the primary (hotter) component, M2 = 1.36(±0.01)M⊙ and R2 = 2.92(±0.04)R⊙ for the secondary (cooler) component. In addition, the orbital period variations of RT CrB are investigated based on all available times of light minima collected from literature and databases. We find that the orbital period exhibits a possible long-term period decrease with a rate of dP/dt = −3.11 × 10−7 d yr−1, suggesting that RT CrB is undergoing an angular momentum loss via magnetic braking.