Semi-detached System Research Articles

Fundamental Parameters of a Binary System Consisting of a Red Dwarf and a Compact Star

TIC 157365951 has been classified as a δ Scuti type by the International Variable Star Index. Through the spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope and its light curve, we further discovered that it is a binary system. This binary system comprises a red-dwarf star and a compact star. Through the spectral energy distribution fitting, we determined the mass of the red dwarf star as M 1 = 0.31 ± 0.01M ⊙ and its radius as R 1 = 0.414 ± 0.004R ⊙. By fitting the double-peaked Hα emission, we derived the mass ratio of q = 1.76 ± 0.04, indicating a compact star mass of M 2 = 0.54 ± 0.01M ⊙. Using Phoebe to model the light curve and radial velocity curve for the detached binary system, we obtained a red dwarf star mass of M 1 = 0.29 ± 0.02M ⊙, a radius of R 1 = 0.39 ± 0.04R ⊙, and a Roche–lobe filling factor of f = 0.995 ± 0.129, which is close to the f = 1 expected for a semidetached system. The Phoebe model gives a compact star mass M 2 = 0.53 ± 0.05M ⊙. Constraining the system to be semidetached gives M 1 = 0.34 ± 0.02M ⊙, R 1 = 0.41 ± 0.01R ⊙, and M 2 = 0.62 ± 0.03M ⊙. The consistency of the models is encouraging. The value of the Roche–lobe filling factor suggests that there might be ongoing mass transfer. The compact star mass is as massive as a typical white dwarf.

INVESTIGATION ON FOUR CONTACT BINARY SYSTEMS AND A SEMI-DETACHED ONE AT THE BEGINNING OF THE CONTACT PHASE

We present B, V, Rc and Ic light curves of four contact binary systems and one semi-detached system. New observations confirm and revise the short-period (0.22–0.25d) of the systems and that all the couple of stars belong to the spectral type K. In J105924 and J164349 a third light was found while the shape of the light curves of four systems (excluding J105924) suggest the presence of inhomogeneities on the surface of one component which confirms that the systems are active. Also they are observed at low orbital inclination i∈ (41°, 62°). Temperature differences range is ΔT∈(4,640)K and mass ratios q∈(0.20, 0.75). Absolute parameters are estimated using statistical diagrams. Systems follow the general pattern of the relative subtype of W Ursae Majoris systems. The sum of the component masses of four systems is below the mass limit of 1.0 – 1.2M☉ assumed for the known contact binary stars, this tells us that they belong to the class low mass contact binaries.

An Investigation of six contact binary systems and a semi-detached one

We present a photometric analysis of six W Ursae Majoris contact binaries and one semi-detached system using multifilter CCD observations. The data were obtained with the 0.25 m Schmidt Cassegrain telescope at the observatory Stazione Astronomica Betelgeuse (SAB) in Magnago, Italy, and the 30-cm Ritchey Chretien Astrograph at the IRIDA observatory (IO) of the NAO Rozhen in Bulgaria. We applied the Wilson–Devinney code to model the light curves and derive the orbital and physical parameters of the systems. Four of the contact binaries belong to the W sub-type and two to the A sub-type, and all are in thermal contact. 2MASS J23194851+3603503 has a very low mass ratio q = 0.093 and a fill-out factor of f = 71.4%, whereas the other contact binaries have mass ratios between 0.2 and 0.38 and fill-out factors between 8% and 39%. 2MASS J04525351+6246069 is a semi-detached system with q = 0.125 and a temperature difference of 540 K between the components. We also estimated the absolute elements of all seven eclipsing binaries.

Observational mapping of the mass discrepancy in eclipsing binaries: Selection of the sample and its photometric and spectroscopic properties

Context. Eclipsing spectroscopic double-lined binaries are the prime source of precise and accurate measurements of masses and radii of stars. These measurements provide a stringent test for models of stellar evolution that are consistently reported to contain major shortcomings. Aims. The mass discrepancy observed for eclipsing spectroscopic double-lined binaries is one of the manifestations of the shortcomings in stellar evolution models. The problem reflects the inability of the models to accurately predict the effective temperature and surface gravity or luminosity of a star for a given mass. Our ultimate goal is to provide an observational mapping of the mass discrepancy and to propose a recipe for its solution. Methods. We initiated a spectroscopic monitoring campaign of 573 candidate eclipsing binaries classified as such based on their TESS light curves. In this work, we present a sub-sample of 83 systems for which orbital phase-resolved spectroscopy has been obtained and subsequently analysed with the methods of least-squares deconvolution and spectral disentangling. In addition, we employed TESS space-based light curves to provide photometric classification of the systems according to the type of their intrinsic variability. Results. We confirmed 69 systems as being either spectroscopic binaries or higher-order multiple systems. We classified twelve stars as single, and we found two more objects that cannot be decisively classified as intrinsically variable single or binary stars. Moreover, 20 eclipsing binaries were found to contain at least one component that exhibits stellar oscillations. Spectroscopic orbital elements were obtained with the spectral disentangling method and reported for all systems classified as either SB1 or SB2. The sample presented in this work contains both detached and semi-detached systems and covers a range in the effective temperature and mass of the star of Teff ∊ [7000,30 000] K and M ∊ [1.5, 15] M⊙, respectively. Conclusions. Based on a comparison of our own results with those published in the literature for well-studied systems, we conclude that there is an appreciable capability of the spectral disentangling method to deliver precise and accurate spectroscopic orbital elements from as few as six to eight orbital phase-resolved spectroscopic observations. Orbital solutions obtained this way are accurate enough to deliver age estimates with an accuracy of 10% or better for intermediate-mass F-type stars, an important resource for the calibration of stellar evolution models for future space-based missions, such as PLATO. Finally, despite the small size relative to the 573 systems that we will ultimately monitor spectroscopically, the sample presented in this work is already suitable to kick off observational mapping of the mass discrepancy in eclipsing binaries.

Detection of Pulsation and Additional Components in Eclipsing Binary RS Sct

The eclipsing binary star RS Sct is a semi-detached system of the β Lyrae type. This system was photometered for six nights in 2019 August, and 2020 June and August. The light and radial velocity curves were simultaneously analyzed to obtain the absolute physical and orbital parameters of the system, and the system geometry was determined. In this system, the primary component has filled its inner Roche lobe and the secondary component is close to filling it. Moreover, the change in the orbital period of this system was investigated. The presence of the third or fourth components and the mass transfer between the two components affect the orbital period of the system. In addition, the pulsation of the primary component was detected. Also, several frequencies with high signal-to-noise ratios were identified. According to the position of the primary component in the H-R diagram and the value of the obtained frequencies, this component is likely a delta-Scuti pulsator.

Six Newly Discovered Eclipsing Binary Systems in the TESS field

We present the first detailed investigation of six eclipsing binary systems in the TESS field. The TESS light curves of the targets are analyzed by determining the initial effective temperatures via SED fits. The absolute parameters are derived and the systems are compared to well-known binaries of the same type. Results show that CD-58791, CD-621257 and TYC 9356-355-1 are detached binary systems. CD-54942 and UCAC4 136-007295 are contact binaries while TYC 8508-1413-1 is a semidetached system.

Semi-detached double-lined eclipsing binaries with Gaia DR3 data

Semi-detached double-lined eclipsing binaries (SD DLEB) play an important role in our understanding of basic properties of interacting binaries. We have collected data on semi-detached systems with available light and radial velocity curve solutions, and have compiled the most comprehensive list of SD DLEB, containing astrophysical and orbital parameters. The goal of this work was to make a cross-identification of the catalogued objects with Gaia DR3 archive. We have supplied our catalogue with data from Gaia DR3 as well as multicolor photometry from SIMBAD, and make a preliminary analysis of the results.

Updated modelling and refined absolute parameters of the oscillating eclipsing binary AS Eri

ABSTRACT We present a new study of the Algol-type eclipsing binary system AS Eri based on the combination of the MOST and TESS light curves and a collection of very precise radial velocities obtained with the spectrographs HERMES operating at the Mercator telescope, La Palma, and TCES operating at the Alfred Jensch telescope, Tautenburg. The primary component is an A3 V-type pulsating, mass-accreting star. We fitted the light and velocity data with the package phoebe, and determined the best-fitting model adopting the configuration of a semi-detached system. The orbital period has been improved using a recent (O-C) analysis and the phase shift detected between both light curves to the value 2.6641496 ± 0.0000001 d. The absence of any cyclic variation in the (O-C) residuals confirms the long-term stability of the orbital period. Furthermore, we show that the models derived for each light curve separately entail small differences, e.g. in the temperature parameter Teff,2. The high quality of the new solutions is illustrated by the residuals. We obtained the following absolute component parameters: L1 = 14.125 L⊙, M1 = 2.014 M⊙, R1 = 1.733 R⊙, log g1 = 4.264, L2 = 4.345 L⊙, M2 = 0.211 M⊙, R2 = 2.19 R⊙, log g2 = 3.078 with Teff,2/Teff,1 = 0.662 ± 0.002. Although the orbital period appears to be stable on the long term, we show that the light-curve shape is affected by a years-long modulation which is most probably due to the magnetic activity of the cool companion.

The detached binary IR cassiopeiae

The first radial velocity curves for IR Cas have been obtained. Combined with new light curve data, simultaneous Roche-based light curve analyses have been carried out using the 2003 version of the Wilson-Devinney code. New values for the masses, radii, and luminosities have been obtained: M1 = 1.40 (4) M ʘ, M 2 = 1.20 (3) M ʘ, R1 = 1.75 (2) Rʘ, R2 = 1.62 (2) Rʘ, L1 = 5.11 (9) L ʘ, and L 2 = 2.56 (16) L ʘ. Comparison with the results from the photometric only analysis of Li et al. (2014) reveal remarkable agreement; however, they concluded a semi-detached system, whereas this paper concludes that this is a detached system. Reference to the plotted log L vs log T data of Yakut and Eggleton (2005) suggests that both stars are evolved.

Photometric study of semi-detached eclipsing binary TW Cas based on TESS photometry

TW Cas is an eclipsing binary that contains B-type and solar-like components with an orbital period of 1.42832665 d and mass ratio of 0.4873. The semi-detached configuration makes it a key goal for understanding Algol-type eclipsing binaries evolution. However, the physical parameters and evolutionary state of TW Cas are still unknown. W–D differential correction program was employed to give orbital parameters and configuration and extend our knowledge of TW Cas evolution. We present light curves and 64 eclipsing times observed by Transiting Exoplanet Survey Satellite (TESS) telescope. Photometric analyses of the TESS light curve suggest that TW Cas is a semi-detached system where the less massive component is filling its critical Roche lobe, and a large dark spot is found on the polar of the less massive one. By using all light minima times, it is detected that the O−C curve shows an upward parabolic change while a cyclic oscillation is superimposed with an amplitude of 0.024585 days and a period of 113.41 yr. The upward parabolic change may indicate a long-term increase of the orbital period at a rate of 1.41 ×10−7 days yr−1, which reveals a rapid mass transfer between the components. The cyclic oscillation might result from the light-travel-time effect owing to the presence of a third body. The semi-detached configuration that less mass component fills its Roche lobe, together with the long-term increase of orbital period and the presence of a large dark spot on the less massive component indicates that TW Ca is at a critical stage of evolution after a mass ratio inversion.

A black hole detected in the young massive LMC cluster NGC 1850

ABSTRACT We report on the detection of a black hole (NGC 1850 BH1) in the ∼100-Myr-old massive cluster NGC 1850 in the Large Magellanic Cloud. It is in a binary system with a main-sequence turn-off star (4.9 ± 0.4 M⊙), which is starting to fill its Roche lobe and is becoming distorted. Using 17 epochs of Very Large Telescope/Multi-Unit Spectroscopic Explorer observations, we detected radial velocity variations exceeding 300 km s−1 associated with the target star, linked to the ellipsoidal variations measured by the fourth phase of the Optical Gravitational Lensing Experiment in the optical bands. Under the assumption of a semidetached system, the simultaneous modelling of radial velocity and light curves constrains the orbital inclination of the binary to 38° ± 2°, resulting in a true mass of the unseen companion of $11.1_{-2.4}^{+2.1}\,{\rm M}_{\odot }$. This represents the first direct dynamical detection of a black hole in a young massive cluster, opening up the possibility of studying the initial mass function and the early dynamical evolution of such compact objects in high-density environments.

A photometric study of two neglected eclipsing binaries

We present the first BVR photometry, period variation and photometric light curve analysis of two poorly studied eclipsing binaries, V1321 Cyg and CR Tau. Observations were carried out from November 2017 to January 2020 at the observatory of Uzhhorod National University. Period variations were studied using all available early published as well as our minima times. We used the newly developed ELISa code for the light curve analysis and determination of photometric parameters for both systems. We found that V1321 Cyg is a close detached eclipsing system with a low photometric mass ratio of q = 0.28 which suggests that the binary is a post-mass transfer system. No significant period changes in this system are detected. CR Tau is, on the other hand, a semi-detached system where the secondary component almost fills its Roche lobe. We detected a long-term period increase at a rate of 1.49 × 10−7 d yr−1, which supports mass transfer from the lower mass secondary component to the more massive primary.

Rapid mass transfer between the twin components in the hierarchical triple system GK Cep

ABSTRACT GK Cep is an eclipsing binary that contains two A-type components with an orbital period of 0.936 d. The high mass ratio and the contact or near-contact configuration make it a key target to understand binary evolution. However, the physical properties and evolutionary state are still unknown. Here we present the UV light curve obtained by using the lunar-based ultraviolet telescope (LUT) and several eclipse times obtained with the Sino-Thai 70-cm telescope and the 1.0-m telescope at Yunnan Observatories. Analysis of the LUT light curve suggests that GK Cep is a near-contact semidetached system where the slightly less massive component is the hotter one that is filling the critical Roche lobe. Meanwhile, a hotspot is found on the neck of the more massive but cooler component. By using all available times for the light minimum, it is detected that the O–C curve shows a cyclic oscillation while it undergoes an upward parabolic change. The increase of the orbital period, the high mass ratio, the semidetached configuration with a lobe-filling less massive component, and the presence of a hotspot on the more massive component all suggest that GK Cep is in a key evolutionary state just after the shortest-period evolutionary stage during the rapid mass transfer. The cyclic change in the O–C curve reveals that GK Cep contains a solar-type stellar companion in a triply hierarchical system that is in agreement with the spectroscopic result. The third body contributes about 2.6 per cent to the total light of the triple system.

Flaring and Spot Activities on the Semi-detached Binary System KIC 06852488

Abstract The continuous and unbroken time-series photometry data of Kepler and the Transiting Exoplanet Survey Satellite (TESS) provide a good opportunity to study the continuous variations in the light curve of binary stars. This paper reports the discoveries of the correlation between the two maxima on the light curve of KIC 06852488 and the correlation between the O’Connell effect and the O − C curve. The Max I and Max II vary with a same cycle length of ∼2000 days and a 180° phase difference, and the variation of the Max II coincides with the O − C curve of the primary light minima. After analyzing the Kepler and TESS light curves, it is detected that this binary is a semi-detached system with a mass ratio of 0.4622(±0.0036). The secondary component is filling its critical Roche lobe, while the primary component is only filling 12.25(±0.10)% of the lobe volume that contributes more than 85% luminosity of the total system. The variation of the O’Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component. It is found that their positions are symmetrical with the inner Lagrange L1 point. After subtracting the binary brightness changes, six optical flares are detected that come from the cool secondary. We calculated the energy of flares and found that all of the flares are superflares. Both the flares and an evolving dark spot on the lobe-filling secondary component make the system a very interesting source to investigate the effects of binary interaction on the magnetic activities.

The Tarantula Massive Binary Monitoring

Context. Accurate stellar parameters of individual objects in binary systems are essential to constrain the effects of binarity on stellar evolution. These parameters serve as a prerequisite to probing existing and future theoretical evolutionary models. Aims. We aim to derive the atmospheric parameters of the 31 double-lined spectroscopic binaries in the Tarantula Massive Binary Monitoring sample. This sample, composed of detached, semi-detached and contact systems with at least one of the components classified as an O-type star, is an excellent test-bed to study how binarity can impact our knowledge of the evolution of massive stars. Methods. In the present paper, 32 epochs of FLAMES/GIRAFFE spectra are analysed by using spectral disentangling to construct the individual spectra of 62 components. We then apply the CMFGEN atmosphere code to determine their stellar parameters and their helium, carbon, and nitrogen surface abundances. Results. Among the 31 systems that we study in the present paper, we identify between 48 and 77% of them as detached, likely pre-interacting systems, 16% as semi-detached systems, and between 5 and 35% as systems in or close to contact phase. Based on the properties of their components, we show that the effects of tides on chemical mixing are limited. Components on longer-period orbits show higher nitrogen enrichment at their surface than those on shorter-period orbits, in contrast to expectations of rotational or tidal mixing, implying that other mechanisms play a role in this process. For semi-detached systems, components that fill their Roche lobe are mass donors. They exhibit higher nitrogen content at their surface and rotate more slowly than their companions. By accreting new material, their companions spin faster and are likely rejuvenated. Their locations in the N − v sin i diagram tend to show that binary products are good candidates to populate the two groups of stars (slowly rotating, nitrogen-enriched objects and rapidly rotating non-enriched objects) that cannot be reproduced through single-star population synthesis. Finally, we find no peculiar surface abundances for the components in (over-)contact systems, as has been suggested by evolutionary models for tidal mixing. Conclusions. This sample, consisting of 31 massive binary systems, is the largest sample of binaries composed of at least one O-type star to be studied in such a homogeneous way by applying spectral disentangling and atmosphere modelling. The study of these objects gives us strong observational constraints to test theoretical binary evolutionary tracks.

The Tarantula Massive Binary Monitoring

Context. A high fraction of massive stars are found to be binaries but only a few of them are reported as photometrically variable. By studying the populations of double-lined spectroscopic binaries in the 30 Doradus region, we found a subset of them that have photometry from the OGLE project and that display variations in their light curves related to orbital motions. Aims. The goal of this study is to determine the dynamical masses and radii of the 26 binary components in order to investigate the mass-discrepancy problem and to provide an empirical mass-luminosity relation for the Large Magellanic Cloud (LMC). Methods. We use the PHOEBE programme to perform a systematic analysis of the OGLE V and I light curves obtained for 13 binary systems in the 30 Doradus region. We adopt the effective temperatures, and orbital parameters derived previously to obtain the inclinations of the systems and the parameters of the individual components. Results. Three systems display eclipses in their light curves, while the others only display ellipsoidal variations. We classify two systems as over-contact, five as semi-detached, and four as detached. The two remaining systems have uncertain configurations due to large uncertainties on their inclinations. The fact that systems display ellipsoidal variations has a significant impact on the inclination errors. From the dynamical masses, luminosities, and radii, we provide LMC-based empirical mass-luminosity and mass-radius relations, and we compare them to other relations given for the Galaxy, the LMC, and the Small Magellanic Cloud. These relations differ for different mass ranges, but do not seem to depend on the metallicity regimes. We also compare the dynamical, spectroscopic, and evolutionary masses of the stars in our sample. While the dynamical and spectroscopic masses agree with each other, the evolutionary masses are systematically higher, at least for stars in semi-detached systems. This suggests that the mass discrepancy can be partly explained by past or ongoing interactions between the stars.

Frequent Flare Events on the Short-period M-type Eclipsing Binary BX Tri

We present long-term, multicolor photometric monitoring and spectroscopic observations of the short-period M-type eclipsing binary BX Tri. Six flare events were recorded over four years from 2014 to 2017. Three of them were detected on one night within an orbital cycle. The strongest one was identified on 2014 December 23. With the amplitudes ΔB = 0.48 mag, ΔV = 0.28 mag, ΔR = 0.10 mag, and ΔI = 0.02 mag, the total energy due to the flare event was measured to be 4.08 (±0.24) × 1034 erg, exceeding the superflare level (1034). Based on the observations, the evolutionary status of the binary system and the long-term orbital period changes were analyzed. It reveals that BX Tri is probably a semidetached system with the primary component filling its Roche lobe. The extremely high occurrence of flare events in the binary could be related to rapid mass transfer between the components.

Physical properties of three short period close binaries: KIC 2715417, KIC 6050116 and KIC 6287172**Discovered by the Kepler Space Telescope

We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass (which approximates the Johnson V-band). Our three systems are KIC 2715417, KIC 6050116 and KIC 6287172. The first system, KIC 2715417, is considered a semi-detached system with the secondary component filling its Roche lobe. The second system, KIC 6050116, is an overcontact system, while the third system, KIC 6287172, belongs to ellipsoidal variables as deduced from the Roche lobe geometry. For photometric analysis, we used the PHOEBE software package, which is based on the Wilson-Devinney code. Due to lack of spectroscopic data, the photometric mass ratios are determined from the analyses of light curves using the q-search method. The absolute parameters are determined using three different methods (Harmanec, Maceroni & Van’tVeer and Gazeas & Niarchos).

Starspots in contact and semi-detached binary systems

AbstractWe investigated the statistical properties of both cool and hot starspots in eclipsing binary stars. The starspot and binary parameters for contact and semi-detached systems were collected from literature, determined on the basis of synthetic light-curve analysis. We examined associations between these parameters. It was found that the cool spots in W-type binaries show properties similar to those of sunspots and starspots generated by dynamos, which differs from those of the cool spots in A-type binaries.The properties of hotspots also differ between the W- and A-type samples. From the physical properties of A- and W-type binaries, we infer that mass transfer is a dominant process for forming the hotspots in A-type binaries, and that both mass transfer and magnetic activity can contribute to the formation of the hotspots in W-type binaries. Our results also indicate that the hotspot size in the A-type sample is correlated with the temperature of spotted stars, orbital period, mass ratio, and fill-out factor.

Turbulence in the Accretion Disks in Semi-Detached Binary Systems with Various Component-Mass Ratios

Results of three-dimensional gas-dynamical numerical simulations of the structure of matter flows in semi-detached binary systems with various component-mass ratios are considered. The main elements of the flows in the models studied are described. The characteristics of density waves inside the accretion disk for various component-mass ratios are considered. The influence of the precessional density wave on the development of instability in the accretion disks and the characteristics of developing turbulence are analyzed. Values of the Shakura–Syunyaev coefficient α for the simulated systems are calculated.