UMa-type Binaries Research Articles

Light curve modeling of the two short period eclipsing binaries ATO J009.3383 + 34.2329 and CRTS J004004.7 + 385531

In this study, we present a detailed photometric analysis of two short-period eclipsing binary systems, ATOJ009.3383 + 34.2329 and CRTSJ004004.7 + 385531. The photometric data for our analysis was obtained from the Zwicky Transient Facility (ZTF) catalogue at gri filters and the Transiting Exoplanet Survey Satellite (TESS) database. Based on our analysis, we classify both systems as W Uma-type binaries, with A-subtype. To estimate the physical and geometrical parameters of these systems, we employ the PHEOBE code. This results in two totally eclipsing systems with degree of inclination (i) of around 68 and 88 deg, respectively. The ATOJ009.3383 + 34.2329 indicates a low mass ratio (q) binary with q = 0.107, while CRTSJ004004.7 + 385531 exhibits a moderate q value of 0.545. A cool spot on the surface of the secondary star of CRTSJ004004.7 + 385531 with a 30% cooler atmosphere of the surrounding surface is detected. This is explained by magnetic activity on the surface of CRTSJ004004.7 + 385531. Our findings reveal overcontact fill-out factor f with 54 and 52% for ATOJ009.3383 + 34.2329 and CRTSJ004004.7 + 385531, respectively. In addition to the light curve modeling, we calculate new epochs and ephemeris for both binary systems. The absolute parameters for the two systems are estimated. Eventually, the systems’ evolutionary status along ZAMS and TAMS are discussed.

Comparative study of the W UMa type binaries S Ant and ε CrA

Abstract Contact binaries challenge contemporary stellar astrophysics with respect to their incidence, structure, and evolution. We explore these issues through a detailed study of two bright examples: S Ant and $\varepsilon$ CrA, that permit high-resolution spectroscopy at a relatively good S/N ratio. The availability of high-quality photometry, including data from the TESS satellite as well as Gaia parallaxes, allows us to apply the Russell paradigm to produce reliable up-to-date information on the physical properties of these binaries. As a result, models of their interactive evolution, such as the thermal relaxation oscillator scenario, can be examined. Mass transfer between the components is clearly evidenced, but the variability of the O’Connell effect over relatively short-time scales points to irregularities in the mass transfer or accretion processes. Our findings indicate that S Ant may evolve into an R CMa type Algol, while the low mass ratio of $\varepsilon$ CrA suggests a likely merger of its components in the not-too-distant future.

Time-sequence Spectroscopy of Epsilon CrA: The 518 nm Mg i Triplet Region Analyzed with Broadening Functions

Abstract High-resolution spectroscopic observations of the W UMa-type binary ϵ CrA obtained as a time-monitoring sequence on four full and four partial nights within two weeks have been used to derive orbital elements of the system and discuss the validity of the Lucy model for description of the radial-velocity data. The observations had more extensive temporal coverage and better quality than similar time-sequence observations of the contact binary AW UMa. The two binaries share several physical properties and show very similar deviations from the Lucy model: the primary component is a rapidly rotating star almost unaffected by the presence of the secondary component, while the latter is embedded in a complex gas flow and appears to have its own rotation-velocity field, in contradiction to the model. The spectroscopic mass ratio is found to be larger than the one derived from the light-curve analysis, as in many other W UMa-type binaries, but the discrepancy for ϵ CrA is relatively minor, much smaller than for AW UMa. The presence of the complex velocity flows contradicting the assumption of solid-body rotation suggests a necessity of modification to the Lucy model, possibly along the lines outlined by Stȩpień in his concept of energy transfer between the binary components.

Reanalysis of the orbital period variations of two DLMR overcontact binaries: FG Hya and GR Vir

We investigate orbital period changes of two deep, low mass ratio (DLMR) overcontact W UMa-type binaries, FG Hya and GR Vir. It is found that the orbital period of FG Hya shows a cyclic change with a period of . The cyclic oscillation may be due to a third body in an eccentric orbit, while the orbital period of GR Vir shows a periodic variation with a period of and an amplitude of A = 0.0352 d. The periodic variation of GR Vir can be interpreted as a result of either the light-time effect of an unseen third body or the magnetic activity cycle.

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 Ic 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.

Multi-color photometric investigation of the totally eclipsing binary NO Camelopardalis

Abstract Multi-color photometric light curves of NO Camelopardalis in V, RC, and IC bands are obtained and analyzed simultaneously using the Wilson–Devinney program. The solutions suggest that NO Cam is an A-subtype overcontact binary with a mass ratio of q = 0.439 and a contact degree of f = 55.5%. The small temperature difference (ΔT = 44 K) between its two components indicates that the system is under thermal contact. The high orbital inclination (i = 84${^{\circ}_{.}}$5) strengthens our confidence in the parameters determined from the light curves. All available times of minimum light are collected and period variations are analyzed for the first time. The O − C curve reveals that its period is increasing continuously at a rate of dP/dt = +1.46 × 10−9, which can be explained by mass transfer from the less massive component to the more massive one. After the upward parabolic variation is subtracted, the residuals suggest that there may be a cyclic variation with a period of 2.23 yr and an amplitude of A3 = 0.00153 d, which may due to the light-travel-time effect arising from the gravitational influence of a close-in tertiary component. The close-in companion reveals that early dynamic interaction among a triple system may have played a very important role in the formation of the W UMa-type binaries.

Orbital period variations of two W UMa-type binaries: UY UMa and EF Boo

The orbital period variations of two W UMa-type contact binaries, UY UMa and EF Boo, are analyzed by using all available times of light minimum. It is detected that the general trends of their (O−C) curves show an upward parabolic variation, which reveals their continuous period increases at the rates of dP/dt=2.545×10−7 days yr−1 and dP/dt=2.623×10−7 days yr−1, respectively. Meanwhile, UY UMa also shows a cyclic period variation with a small amplitude of A=0.0026 days superposed on the long-term increase. Due to their contact configurations, the secular period increases are interpreted as a result of mass transfer from the less massive component to the more massive one. The cyclic period variation of UY UMa may be interpreted in terms of either the magnetic activity or the light time effect.

A PHOTOMETRIC STUDY OF FOUR RECENTLY DISCOVERED CONTACT BINARIES: 1SWASP J064501.21+342154.9, 1SWASP J155822.10-025604.8, 1SWASP J212808.86+151622.0, AND UCAC4 436-062932

ABSTRACT We present new, high-quality multicolor observations of four recently discovered contact binaries, 1SWASP J064501.21+342154.9, 1SWASP J155822.10-025604.8, 1SWASP J212808.86+151622.0, and UCAC4 436-062932, and analyze their light curves to determine orbital and physical parameters using the modeling program of G. Djurašević. In the absence of spectroscopic observations, the effective temperatures of the brighter components are estimated from the color indices, and the mass ratios are determined with the q-search method. The analysis shows that all four systems are W UMa type binaries in shallow contact configurations, consisting of late-type main-sequence primaries and evolved secondaries with active surface regions (dark or bright spots) resulting from magnetic activity or ongoing transfer of thermal energy between the components. We compare the derived orbital and stellar parameters for these four variables with a large sample of previously analyzed W UMa stars and find that our results fit it well.

Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light variations of both stars show the O'Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney (WD) code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R1 = 1.24 ± 0.01 R⊙, R2 = 1.11 ± 0.02 R⊙, and M1 = 1.24 ± 0.02 M⊙, M2 = 0.96 ± 0.05 M⊙ and for star ID494 of R1 = 1.22±0.02R⊙, R2 = 0.81±0.01 R⊙, and M1 = 1.20±0.06 M⊙, M2 = 0.47±0.01 M⊙.

Orbital Period Investigations of Two W UMa-type Binaries: AH Aur and V728 Her

The orbital period changes of two W UMa-type binaries, AH Aur and V728 Her, are investigated based on all available times of the light minimum taken from the databases and literature. It is revealed that the orbital period of AH Aur shows a long-term decrease at a rate of days yr−1. For V728 Her, we find that the orbital period exhibits a secular increase at a rate of days yr−1. The secular period changes suggest that AH Aur and V728 Her are undergoing rapid mass transfer between the primary star and the secondary companion.

TIME SEQUENCE SPECTROSCOPY OF AW UMa. THE 518 nm Mg I TRIPLET REGION ANALYZED WITH BROADENING FUNCTIONS

High resolution spectroscopic observations of AW UMa, obtained on three consecutive nights with the median time resolution of 2.1 minutes, have been analyzed using the Broadening Functions method in the spectral window Doppler images of the system reveal the presence of vigorous mass motions within the binary system; their presence puts into question the solid-body rotation assumption of the contact binary model. AW UMa appears to be a very tight, semi-detached binary; the mass transfer takes place from the more massive to the less massive component. The primary, a fast-rotating star with V sin i = 181.4+\-2.5 km s^-1, is covered by inhomogeneities: very slowly drifting spots and a dense network of ripples more closely participating in its rotation. The spectral lines of the primary show an additional broadening component (called the "pedestal") which originates either in the equatorial regions which rotate faster than the rest of the star by about 50 km s^-1 or in an external disk-like structure. The secondary component appears to be smaller than predicted by the contact model. The radial velocity field around the secondary is dominated by accretion of matter transferred from (and possibly partly returned to) the primary component. The parameters of the binary are: A sin i = 2.73 +/- 0.11 R_odot and M_1 sin^3 i = 1.29 +/- 0.15 M_odot, M_2 sin^3 i = 0.128 +/- 0.016 M_odot. The mass ratio q_rm sp = M_2/M_1 = 0.099 +/- 0.003, while still the most uncertain among the spectroscopic elements, is substantially different from the previous numerous and mutually consistent photometric investigations which were based on the contact model. It should be studied why photometry and spectroscopy give so very discrepant results and whether AW UMa is an unusual object or that only very high-quality spectroscopy can reveal the true nature of W UMa-type binaries.

PHOTOMETRIC ANALYSIS OF OVERCONTACT BINARIES AK HER, HI DRA, V1128 TAU, AND V2612 OPH

We analyze new, high quality multicolor light curves of four overcontact binaries: AK Her, HI Dra, V1128 Tau and V2612 Oph, and determine their orbital and physical parameters using the modeling program of G. Djurasevic and recently published results of radial velocity studies. The achieved precision in absolute masses is between 10 and 20%, and in absolute radii between 5 and 10%. All four systems are W UMa type binaries with bright or dark spots indicative of mass and energy transfer or surface activity. We estimate the distances and the ages of the systems using the luminosities computed through our analysis, and perform an O-C study for V1128 Tau, which reveals a complex period variation that can be interpreted in terms of mass loss/exchange and either the presence of the third body, or the magnetic activity on one of the components. We conclude that further observations of these systems are needed to deepen our understanding of their nature and variability.

Photometric and polarimetric studies of three W UMa-type binaries: FZ Ori, V407 Peg and LP UMa

We present analyses of new optical photometric observations of three W UMa-type contact binaries FZ Ori, V407 Peg and LP UMa. Results from the first polarimetric observations of the FZ Ori and V407 Peg are also presented. The periods of FZ Ori, V407 Peg and LP UMa are derived to be 0.399986, 0.636884 and 0.309898 d, respectively. The O−C analyses indicate that the orbital periods of FZ Ori and LP UMa have increased with the rate of 2.28×10−8 and 1.25×10−6 d yr−1, respectively and which is explained by transfer of mass between the components. In addition to the secularly increasing rate of orbital period, it was found that the period of FZ Ori has varied in sinusoidal way with oscillation period of ∼30.1 yr. The period of oscillations are most likely to be explained by the light-time effect due to the presence of a tertiary companion. Small asymmetries have been seen around the primary and secondary maxima of light curves of all three systems, which is probably due to the presence of cool/hot spots on the components. The light curves of all three systems are analysed by using Wilson-Devinney code (WD) and the fundamental parameters of these systems have been derived. The present analyses show that FZ Ori is a W-subtype, and V407 Peg and LP UMa are A-subtype of the W UMa-type contact binary systems. The polarimetric observations in B, V, R and I bands, yield average values of polarization to be 0.26±0.03, 0.22±0.02, 0.22±0.03 and 0.22±0.05 per cent for FZ Ori and 0.21±0.02, 0.29±0.03, 0.31±0.01 and 0.31±0.04 per cent for V407 Peg, respectively.

SX Aurigae: A close binary at the early stage of contact phase

This study presents analysis of new multi-band light curves of β Lyrae-type eclipsing binary SX Aur. Radial velocities of both components of the system were collected from the literature and simultaneous light curve solutions made to determine the properties of the system and absolute elements of its components. The derived masses and radii of the components are M1=11.3±0.2M⊙, M2=6.9±0.1M⊙, R1=5.32±0.02R⊙ and R2=4.23±0.03R⊙, while the distance of the system is estimated at 1220±75pc. It was found that SX Aur is a shallow-contact binary and thus may be in the stage between β Lyrae and W UMa-type binaries. From O–C based period analysis of SX Aur, it is seen that the period of the system increases at a rate of 0.0055syr−1. The most plausible physical mechanism for this period variation is non-conservative mass transfer from the secondary to the primary component at a rate of 3.13×10−7M⊙yr−1.

On the origin of W UMa type contact binaries – a new method for computation of initial masses

W UMa type binaries have two defining characteristics. These are (i) the effective temperatures of both components are very similar, and (ii) the secondary (currently less massive) component is overluminous for its current mass. We consider the latter to be an indication of its mass before the mass-transfer event. For these stars we define a mass difference ($\delta M$) between the mass determined from its luminosity and the present mass determined from fitting the binary orbit. We compare the observed values of the mass difference to stellar models with mass loss. The range of initial secondary masses that we find for observed W UMa type binaries is 1.3-2.6 M$_{\odot}$. We discover that the A- and the W-subtype contact binaries have different ranges of initial secondary masses. Binary systems with an initial mass higher than $1.8 \pm 0.1$ M$_{\odot}$ become A-subtype while systems with initial masses lower than this become W-subtype. Only 6 per cent of systems violate this behavior. We also obtain the initial masses of the primaries using the following constraint for the reciprocal of initial mass ratio: $0 < 1/q_i < 1$. The range of initial masses we find for the primaries is 0.2-1.5 M$_{\odot}$, except for two systems. Finally in comparing our models to observed systems we find evidence that the mass transfer process is not conservative. We find that only 34 per cent of the mass from the secondary is transferred to the primary. The remainder is lost from the system.

BVRI photometric and polarimetric studies of W UMa type eclipsing binary FO Hydra

We present analysis of optical photometric and polarimetric observations of contact binary system FO Hydra (FO Hya). The computed period of the system is 0.469556±0.000003days. An O–C curve analysis indicates an increase in its period by 5.77×10−8dayyr−1. The photometric light curves are analyzed using Wilson–Devinney code (WD). The present analysis shows that FO Hya is a B-subtype of W UMa type contact binary. The radii and mass of primary and secondary components are found, respectively, to be R1=1.62±0.03 R⊙ and R2=0.91±0.02 R⊙, and M1=1.31±0.07M⊙ and M2=0.31±0.11M⊙. The light curve shape shows small asymmetries around the primary and secondary maxima. This may be due to the presence of dark spots on the components. The polarimetric observations yield average values of its polarization to be 0.18±0.03, 0.15±0.03, 0.17±0.02 and 0.15±0.02% in B, V, R and I bands, respectively. These values are appreciably lower than the typical polarization of W UMa type binaries. We have discussed the possible sources of the observed polarization but in order to arrive at definitive answer to this more phase locked observations are needed.

The Broadening Functions Technique

AbstractEssential assumptions and features of the Broadening Function (BF) technique are presented. A distinction between BF determination and the BF concept and utilization is made. The BF's can be determined in various ways. The approach based on linear deconvolution involving stellar templates, as used during the DDO program (1999 – 2008) is described, but the LSD technique would also give excellent results. The BF concept to prove and/or verify photometric light-curve solutions has so far been very limited to only a few W UMa-type binaries, with AW UMa giving particularly unexpected results.

Photometric study of eclipsing binaries in the Large Magellanic Cloud — I. W UMa type binaries in the Large Magellanic Cloud

Eclipsing binaries are among the most important sources of information on stellar parameters like radii, masses, luminosities, etc. We present the analysis of six W UMa systems discovered in the Large Magellanic Cloud using the Wilson-Devinney method.

Photometric study of W UMa type binaries in the intermediate open cluster NGC 7789

The light curve solutions of two W UMa binary systems in the intermediate open cluster NGC 7789 are presented in this paper. These variables were observed using the 2 m telescope of the IUCAA-Girawali Observatory. The V passband photometric solutions of the two W UMa binaries were obtained using the latest version of the W–D program. The result shows that both systems are H-subtype W UMa binaries with high mass ratios.

Photometric study of W UMa type binaries in the old open cluster Berkeley 39

The study of W UMa binary systems gives a wealth of information about their nature as well as their parent bodies (if any), like clusters. In this paper, we present the I passband photometric solutions of four W UMa binaries in the open cluster Berkeley 39 using the latest version of the W–D program. The result shows that two binary systems are W-subtype W UMa binary systems and the other two systems are H-subtype W UMa binary systems. No third body has been found in any of the four systems. We found a correlation between the period and mass-ratio as well as temperature and mass-ratio for the respective variables, which is similar to the relationship between mass ratio and total mass of the contact binaries as shown by van't Veer and Li et al.