Eclipse Timing Variations Research Articles

On the nature of the eccentric eclipsing binary star SY Phe with a pulsating γ Dor component

ABSTRACT Spectroscopic observations of the eccentric binary system SY Phe were made at the South African Astronomical Observatory in 2019, 2020, and 2021, and its mid-resolution spectra were obtained. The radial velocities of the component stars were measured using the cross-correlation method and Fourier disentangling of the spectra. The spectral type (hence the effective temperature) of the primary star was determined from a model-atmosphere analysis. The radial velocity and Transiting Exoplanet Survey Satellite (TESS) light curves of the system were analysed, and its absolute parameters were derived. A strong (5.2 mmag) periodic signal with a frequency typical of $\gamma$ Dor stars (1.169 cycles per day) dominates the Fourier spectrum of the light curve between the eclipses. Apsidal motion parameters of SY Phe were calculated by studying eclipse timing variations. The Geneva evolution models indicate an evolutionary age of 2 Gyr and solar metallicity for the primary component; however, although the position of the secondary component in the H–R diagram matches the isochrone of 2 Gyr, it appears to have a larger radius and higher effective temperature than expected for its determined mass. Here, the secondary component has too large a radius, which is in accordance with the radius discrepancy problem that has been encountered in other studies, especially in late-type dwarfs, and has not been solved for half a century.

TIC 290061484: A Triply Eclipsing Triple System with the Shortest Known Outer Period of 24.5 Days

We have discovered a triply eclipsing triple-star system, TIC 290061484, with the shortest known outer period, P out, of only 24.5 days. This “eclipses” the previous record set by λ Tauri at 33.02 days, which held for 68 yr. The inner binary, with an orbital period of P in = 1.8 days, produces primary and secondary eclipses and exhibits prominent eclipse timing variations with the same periodicity as the outer orbit. The tertiary star eclipses, and is eclipsed by, the inner binary with pronounced asymmetric profiles. The inclinations of both orbits evolve on observable timescales such that the third-body eclipses exhibit dramatic depth variations in TESS data. A photodynamical model provides a complete solution for all orbital and physical parameters of the triple system, showing that the three stars have masses of 6.85, 6.11, and 7.90 M ⊙, radii near those corresponding to the main sequence, and T eff in the range of 21,000–23,700 K. Remarkably, the model shows that the triple is in fact a subsystem of a hierarchical 2+1+1 quadruple with a distant fourth star. The outermost star has a period of ∼3200 days and a mass comparable to the stars in the inner triple. In ∼20 Myr, all three components of the triple subsystem will merge, undergo a Type II supernova explosion, and leave a single remnant neutron star. At the time of writing, TIC 290061484 is the most compact triple system and one of the tighter known compact triples (i.e., P out/P in = 13.7).

Modelling of eclipsing binary systems with pulsating components and tertiary companions: BF Vel and RR Lep

This research paper presents a comprehensive analysis of RR Lep and BF Vel, two southern short-period, semi-detached, oscillating Algols (oEA stars) that have been shown to be triple systems. We determined the spectral types of the primary components and calculated the radial velocities from spectra observed with the Australian National University's 2.3 m telescope and Wide Field Spectrograph. The spectra of the Na I D doublet confirmed the presence of tertiary components that were apparent in the broadening function analyses. During primary eclipses chromospherical activity in their secondary components was apparent in their H$_ spectra; it was also apparent in the Na I D spectra of BF Vel with its almost complete annular eclipse. Ground-based telescopes were used for observations in several pass bands for photometric analyses. These observations were complemented by data from the Transiting Exoplanet Survey Satellite (TESS) mission, allowing us to model the light curves, followed by a detailed analysis of pulsations. Eclipse-timing variation (ETV) analyses of both systems were used to determine the most likely mechanisms modulating the orbital period. We found mass values of $M_1=2.9$ sun $ and $M_2=0.75$ M$_ sun $ for the components of RR Lep, along with $M_1=1.93$ M$_ sun $ and $M_2=0.97$ M$_ sun $ for those of BF Vel. By integrating information from photometry, spectroscopy, and ETV analysis, we found that tertiary components revolve around both systems. The primary star of RR Lep pulsates in 36 frequencies; of these, five were identified as independent modes, with the dominant one being 32.28 d$^ $. The pulsating component of BF Vel oscillates in 37 frequencies, with the frequency 46.73 d$^ $ revealed as the only independent mode. For both systems, a number of frequencies were found to be related to the orbital frequency. Their physical properties were compared with other oEA stars in mass-radius and Hertzsprung-Russell diagrams, while the pulsational properties of their delta Sct components were compared with currently known systems of this type within the orbital-pulsation period and $ g$-pulsation period diagrams.

Combined light curve and radial velocity analysis of the neglected contact binary S Ant

We present the first combined photometric and spectroscopic solution of the bright southern contact binary S Ant based on the Transiting Exoplanet Survey Satellite (TESS) light curve and the radial velocities from the David Dunlap Observatory survey. S Ant is a W UMa type binary in deep contact, with a mass ratio of 0.34 and a relatively massive and hot F-type primary. Beside the standard modeling of the phase-binned light curve, we also perform “seasonal modeling” where we treat each of the 83 orbital cycles present in the TESS data as a separate light curve. The resulting ensemble of solutions shows evidence of quasi-periodic migration of a long-lived, dark, polar spot. The migration is confirmed independently by eclipse time variations which display remarkably strong correlation with the spot location.

Comprehensive analysis of the eclipsing binaries V527 Dra and V2846 Cyg

ABSTRACT This is the first comprehensive study of the eclipsing binaries V527 Dra and V2846 Cyg, based on radial velocities and ground- and space-based light curves. We perform detailed modeling of these data to derive the absolute parameters and the orbital properties of the two systems. V527 Dra is found to be a semidetached, and V2846 Cyg a contact binary. Both show continual out-of-eclipse variations that can be explained by migrating dark spots of magnetic origin. We also perform the eclipse timing variation (ETV) analysis which reveals that V527 Dra has a tertiary companion whose mass (${\sim} 1 \,{\rm M}_{\odot }$) and orbital inclination (${\sim} 70^{\circ }$) are additionally constrained by radial velocities. The ETV diagram of V2846 Cyg displays a quadratic trend accompanied by a low-amplitude cyclic variation, likely due to a magnetic cycle, although further eclipse times are needed to provide a clearer explanation. Lastly, we demonstrate a correlation between the variations in spot parameters obtained via light curve modelling for individual orbital cycles and the residual ETVs, essentially confirming the assumption of magnetic activity in both systems.

Seven new triply eclipsing triple star systems

Aims. We have identified nearly a hundred close triply eclipsing hierarchical triple star systems from data taken with the space telescope TESS. These systems are noteworthy in that we can potentially determine their dynamical and astrophysical parameters with a high precision. In the present paper, we report the comprehensive study of seven new compact triply eclipsing triple star systems taken from this larger sample: TICs 133771812, 176713425, 185615681, 287756035, 321978218, 323486857, and 650024463. Methods. Most of the data for this study come from TESS observations, but two of them have Gaia measurements of their outer orbits, and we obtained supplemental radial velocity (RV) measurements for three of the systems. The eclipse timing variation curves extracted from the TESS data, the photometric light curves, the RV points, and the spectral energy distribution (SED) are combined in a complex photodynamical analysis to yield the stellar and orbital parameters of all seven systems. Results. Four of the systems are quite compact with outer periods in the range of 41–56 days. All of the systems are substantially flat, with mutual inclination angles of ≲2°. Including the systems reported in this work, we have now studied in considerable detail some 30 triply eclipsing triples with TESS, and are accumulating a meaningful census of these systems.

Simultaneous Photometric and Spectroscopic Analysis of V505 Lacertae, a Photospherically and Chromospherically Active Contact Binary Star

New BVR photometric and high-resolution spectroscopic observations of V505 Lac are presented with Transiting Exoplanet Survey Satellite (TESS) photometric data. The orbital period has experienced a secular decrease during the past 16 yr. A clear anticorrelation in the primary and secondary eclipse timing variation (PSETV) obtained from the TESS data is also identified. A double-lined radial velocity (RV) curve is secured, and the effective temperatures of the less- and more-massive stars (Stars 1 and 2, respectively) are measured. Using a spectral subtraction technique, excess emissions are detected in the time-series Ca ii H and K and Hα lines for Star 2. Simultaneous analysis of the light and RV curves using the Wilson–Devinney (WD) code reveals that V505 Lac is a photospherically and chromospherically active W-subtype contact binary system. The component-star masses and radii are determined to an accuracy of approximately 1%. The WD spot model is individually applied to 221 light curves segmented from the TESS data so as to derive the spot parameters of a cool spot on Star 2. The combined variations in both longitude and colatitude among the spot parameters appear to be strongly associated with those of both the anticorrelation in the PSETV and the O’Connell effect in the TESS light curves. Robust negative linear relationships between the PSETV anticorrelation size and the O’Connell effect magnitude are found for the first time. Mass–radius, mass–luminosity, and mass ratio–mass diagrams of contact binaries, along with the mass ratio frequency distribution, are presented in an attempt to elucidate the evolutionary characteristics of these systems.

Eclipse-timing study of new hierarchical triple star candidates in the northern continuous viewing zone of TESS

Aims. We compiled a list of more than 3500 eclipsing binaries located in and near the northern continuous viewing zone (NCVZ) of the TESS space telescope that have sufficient TESS photometry to search for additional hidden components in these systems. In addition to discovering their hierarchical nature, we also determined their orbital parameters and analyzed their distributions. Methods. We obtained the TESS light curves of all targets in an automated way by applying convolution-aided differential photometry on the TESS full-frame images from all available sectors up to sector 60. Using a new self-developed Python GUI, we visually confirmed all of these light curves, determined the eclipsing periods of the objects, and calculated their eclipse-timing variations (ETVs). The ETV curves were used in order to search for nonlinear variations that could be attributed to a light travel-time effect (LTTE) or dynamical perturbations caused by additional components in these systems. We preselected 351 such candidates and modeled their ETVs with the analytic formulae of pure LTTE or with a combination of LTTE and dynamical perturbations. Results. We were able to fit a model solution for the ETVs of 135 hierarchical triple candidates, 10 systems of which were known from the literature, and the remaining 125 systems are new discoveries. These systems include some more noteworthy ones, such as five tight triples that are very close to their dynamical stability limit with a period ratio lower than 20, and three newly discovered triply eclipsing triples. We point out that dynamical perturbations occur in GZ Dra, which we found to be a triple, and that the system is one of the most strongly inclined systems known in the literature, with im = 58° ±7°. We also compared the distributions of some orbital parameters from our solutions with those from a previous Kepler sample. Finally, we verified the correlations between the available parameters for systems that have Gaia non-single star orbital solutions with those from our ETV solutions.

Unveiling hidden companions in post-common-envelope binaries: A robust strategy and uncertainty exploration

Context. Some post-common-envelope binaries (PCEBs) are binary stars with short periods that exhibit significant period variations over long observational time spans. These eclipse timing variations (ETVs) are most likely to be accounted for by the presence of an unseen massive companion, potentially of planetary or substellar nature, and the light-travel time (LTT) effect. The existence of such companions challenges our current understanding of planetary formation and stellar evolution. Aims. In this study, our main objective is to describe the diversity of compatible nontransit companions around PCEBs and explore the robustness of the solutions by employing tools for uncertainty estimation. We select the controversial data of the QS Vir binary star, which previous studies have suggested hosts a planet. Methods. We employ a minimizing strategy, using genetic algorithms to explore the global parameter space followed by refinement of the solution using the simplex method. We evaluate errors through the classical Markov chain Monte Carlo (MCMC) approach and discuss the error range for parameters, considering the 1σ values obtained from the minimization. Results. Our results highlight the strong dependence of ETV models for close binaries on the dataset used, which leads to relatively loose constraints on the parameters of the unseen companion. We find that the shape of the O – C curve is influenced by the dataset employed. We propose an alternative method to evaluate errors on the orbital fits based on a grid search surrounding the best-fit values, obtaining a wider range of plausible solutions that are compatible with goodness-of-fit statistics. We also analyze how the parameter solutions are affected by the choice of the dataset, and find that this system continuously changes the compatible solutions as new data are obtained from eclipses. Conclusions. The best-fit parameters for QS Vir correspond to a low-mass stellar companion (57.71 Mjup ranging from ~40 to ~64 Mjup) on an eccentric orbit (e = 0.91−0.17+0.07) with a variety of potential periods (P = 16.69−0.42+0.47 yr.). Most solutions within 1σ exhibit regular orbits, despite their high eccentricity. Additional observations are required to accurately determine the period and other parameters of the unseen companion. In this context, we propose that a fourth body should not be modeled to fit the data, unless new observations considerably modify the computed orbital parameters. This methodology can be applied to other evolved binary stars suspected of hosting companions.

Six new eccentric eclipsing systems with a third body

We present the discovery of six new triple stellar system candidates composed of an inner eccentric-orbit eclipsing binary with an apsidal motion. These stars were studied using new, precise TESS light curves and a long-term collection of older photometric ground-based data. These data were used for the monitoring of ETVs (eclipse timing variations) and to detect the slow apsidal movements along with additional periodic signals. The systems analysed were ASASSN-V J012214.37+643943.3 (orbital period 2.01156 d, eccentricity 0.15, third body with 3.3 yr period); ASASSN-V J052227.78+345257.6 (2.42673 d, 0.35, 3.2 yr); ASASSN-V J203158.98+410731.4 (2.53109 d, 0.20, 2.7 yr); ASASSN-V J230945.10+605349.3 (2.08957 d, 0.18, 2.3 yr); ASASSN-V J231028.27+590841.8 (2.41767 d, 0.43, 4.9 yr); and NSV 14698 (3.30047 d, 0.147, 0.5 yr). In the system ASASSN-V J230945.10+605349.3, we detected a second eclipsing pair (per 2.99252 d) and found adequate ETV for the pair B, proving its 2+2 bound quadruple nature. All of these detected systems deserve special attention from long-term studies for their three-body dynamics since their outer orbital periods are not too long and because some dynamical effects should be detectable during the next decades. The system NSV 14698 especially seems to be the most interesting from the dynamical point of view due to it having the shortest outer period of the systems we studied, its fast apsidal motion, and its possible orbital changes during the whole 20th century.

Eclipse timing variations of evolved eclipsing binaries: potential targets for meter-sized telescopes in the light of TESS observations

Eclipse timing variations of evolved eclipsing binaries: potential targets for meter-sized telescopes in the light of TESS observations

Investigating Period Variability Mechanisms in Eclipsing Binary Stars through Eclipsing Time Variation Analysis: A Case Study of TZ Bootis

We present an effective strategy for extensive analysis of eclipsing time variations (ETVs) using modern and sophisticated optimization methods that comprise a set of tools to investigate period variability mechanisms in eclipsing binary stars such as the light-time effect, the Applegate mechanism, and mass transfer. We implement these methods for the first time assuming that the above mechanisms can act simultaneously in the puzzling W UMa–type binary star TZ Bootis by using archival and new TESS data spanning 75 yr and reexamining the up-to-date ETVs. Preliminary analysis of the TESS data revealed for the first time the presence of a second binary in agreement with previous spectroscopic data and astrometric results from Gaia DR3. We consider the most credible scenario for the ETV: two stellar circumbinary companions of minimum masses M 3 = 0.5 M ☉ and M 4 = 0.14 M ☉ in highly eccentric orbits e 3 = 0.70 and e 4 = 0.82 with periods P 3 = 38 yr and P 4 = 20 yr along with a 24 yr magnetic activity of the secondary component and a long-term period increase (dP/dt = 1.2 × 10−8 days yr−1), interpreted as a conservative mass transfer from the secondary to the primary component at a rate of dM 1/dt = 3.7 × 10−9 days yr−1. Further spectroscopic observations, analytical modeling of the second pair, and ETV analysis of both pairs are needed to investigate the quadruple nature of the system.

Photodynamical Modeling of the Compact, Multiply Eclipsing Systems KIC 5255552, KIC 7668648, KIC 10319590, and EPIC 220204960

We present photodynamical models of four eclipsing binary systems that show strong evidence of being members of higher-order multiple systems via their strong eclipse timing variations and/or via the presence of extra eclipse events. Three of these systems are from the main Kepler mission, and the other is from the K2 mission. We provide some ground-based radial velocities measurements for the three Kepler systems and make use of recent light curves from the TESS mission. Our sample consists of two 2 + 1 systems and two 2 + 2 systems. The first 2 + 1 system, KIC 7668648, consists of an eclipsing binary (Pbin = 27.8 days) with late-type stars (M1=0.8403±0.0090M⊙, R1=1.0066±0.0036R⊙ and M2=0.8000±0.0085M⊙, R2=0.8779±0.0032R⊙) with a low-mass star (M3=0.2750±0.0029M⊙, R3=0.2874±0.0010R⊙) on a roughly coplanar outer orbit (P3=208 days). There are several eclipse events involving the third star that allow for the precise determination of the system parameters. The second 2 + 1 system, KIC 10319590, consists of a binary (Pbin=21.3 days) with late-type stars (M1=1.108±0.043M⊙, R1=1.590±0.019R⊙ and M2=0.743±0.023M⊙, R2=0.7180±0.0086R⊙) that stopped eclipsing about a third of the way into the nominal Kepler mission. We show here that the third star in this system is a Sun-like star (M3=1.049±0.038M⊙, R3=1.39±0.11R⊙) on an inclined outer orbit (P3=456 days). In this case, there are no extra eclipse events. We present the first comprehensive solution for KIC 5255552 and demonstrate that it is a 2 + 2 system consisting of an eclipsing binary (Pbin,1=32.5 days) with late-type stars (M1=0.950±0.018M⊙, R1=0.9284±0.0063R⊙ and M2=0.745±0.014M⊙, R2=0.6891±0.0051R⊙) paired with a non-eclipsing binary (Pbin,2=33.7 days) with somewhat lower-mass stars (M3=0.483±0.010M⊙, R3=0.4640±0.0036R⊙ and M4=0.507±0.010M⊙, R4=0.4749±0.0031R⊙). The two binaries, which have nearly coplanar orbits, orbit their common barycenter on a roughly aligned outer orbit (Pout=878 days). There are extra eclipse events involving the component stars of the non-eclipsing binary, which leads to relatively small uncertainties in the system parameters. The second 2 + 2 system, EPIC 220204960, consists of a pair of eclipsing binaries (Pbin,2=13.3 days, Pbin,2=14.4 days) that both consist of two low-mass stars (M1=0.54M⊙, R1=0.46R⊙, M2=0.46M⊙, R2=0.37R⊙ and M3=0.38M⊙, R3=0.40R⊙, M4=0.38M⊙, R4=0.37R⊙) that orbit their common barycenter on a poorly determined outer orbit. Because of the relatively short time span of the observations (≈80 days for the photometry and ≈70 days for the radial velocity measurements), the masses and radii of the four stars in EPIC 220204960 can only be determined with accuracies of ≈10% and ≈5%, respectively. We show that the most likely period of the outer orbit is 957 days, with a 1σ range of 595 to 1674 days. We can only place weak constraints on the mutual inclinations of the orbital planes, and additional radial velocity measurements and/or additional eclipse observations would allow for much tighter constraints on the properties of the outer orbit.

Observational Detection of Higher-Order Secular Perturbations in Tight Hierarchical Triple Stars

In this work, we search for observational evidence of higher-order secular perturbations in three eclipsing binaries. These are slightly eccentric binaries, and they form the inner pairs of tight, compact, hierarchical triple star systems. Simultaneously, we analyze the high-precision satellite (Kepler and TESS) light curves; eclipse timing variations; combined spectral energy distributions (through catalog passband magnitudes); and, where available, radial velocities of KICs 9714358, 5771589, and TIC 219885468. Besides the determination of the robust astrophysical and dynamical properties of the three systems, we find evidence that the observed unusual eclipse timing variations of KIC 9714358 are a direct consequence of the octupole-order secular eccentricity perturbations forced by unusual, resonant behavior between the lines of the apsides of the inner and outer orbital ellipses. We also show that, despite its evident cyclic eclipse depth variations, KIC 5771589 is an almost perfectly coplanar system (to within 0.3∘), and we explain the rapid eclipse depth variations with the grazing nature of the eclipses. Finally, we find that the inner pair of TIC 219885468 consists of two twin stars; hence, in this triple there are no octupole-order three-body perturbations. Moreover, we show that this triple is also coplanar on the same level as the former one, but due to its deep eclipses, it does not exhibit eclipse depth variations. We intend to follow this work up with further analyses and a quantitative comparison of the theoretical and the observed perturbations.

KIC 9028474: A Long-period Eclipsing Binary on a Highly Eccentric Orbit

We present a comprehensive analysis of a very long-period (124.93669 days) eclipsing binary KIC 9028474, which is composed of F9V+G1V components on a highly eccentric (e = 0.82029) orbit. Masses and radii of the primary and the secondary components are M 1 = 1.18 ± 0.04 M ⊙, M 2 = 1.04 ± 0.03 M ⊙, R 1 = 1.52 ± 0.02 R ⊙, and R 2 = 1.11 ± 0.01 R ⊙, respectively. Eclipse time variations show the presence of apsidal motion, which in turn shows the existence of a third body in a relatively close orbit. Simultaneous analysis of infrared spectra and space photometry reveals that the primary component is about to leave the main sequence, indicating an age of 5.2 ± 0.8 Gyr for the system. Theoretical evaluation of the observed eccentricity indicates that the components of KIC 9028474 will end their whole life much before the orbital circularization is achieved. Given the limited resolution of the spectra, we can only place an upper limit on the rotational velocities of each star, thus a theoretical evaluation of the synchronization of the components.

Solaris photometric survey: Search for circumbinary companions using eclipse timing variations

ABSTRACT Eclipse timing variations (ETVs) have been a successful tool for detecting circumbinary companions to eclipsing binaries (EBs). While TESS and Kepler have been prolific for ETV searches, they sometimes can be limited by time and sky coverage, a limitation that can be addressed by specialized ground-based ETV surveys. We present the initial results from the Solaris photometric survey, which uses four 0.5-m robotic telescopes in the Southern hemisphere to look for circumbinary companions. We present the method of light-curve extraction, detrending, and EB modelling using observations from the Solaris network. Using these light curves, we extract precise eclipse timings for seven EBs and look for companions using a Lomb–Scargle periodogram search. We find two possible periodic signals for the target GSC 08814–01026. With the system having strong activity, we check for the feasibility of orbital solutions at these two periods. We find that the 245 ± 1 d period is due to an M dwarf-mass companion. This makes GSC 08814–01026 a candidate compact hierarchical triple system. The other periodic signal at 146 ± 1 d is an artefact of stellar activity.

101 eclipsing quadruple star candidates discovered in TESS full frame images

ABSTRACT We present our second catalogue of quadruple star candidates, containing 101 systems discovered in TESS Full-Frame Image data. The targets were initially detected as eclipsing binary stars with the help of supervised machine learning methods applied to sectors (Sectors 1 through 54). A dedicated team of citizen scientists subsequently identified through visual inspection two sets of eclipses following two different periods. All 101 systems presented here pass comprehensive photocenter motion tests confirming that both sets of eclipses originate from the target star. Some of the systems exhibit prominent eclipse time variations suggesting dynamical interactions between the two component binary stars. One target is an eclipsing quintuple candidate with a (2 + 1) + 2 hierarchical configuration, such that the (2 + 1) subsystem produces eclipses on the triple orbit as well. Another has recently been confirmed as the second shortest period quadruple reported to date. This catalogue provides ephemerides, eclipse depths and durations, sample statistics, and highlights potentially interesting targets for future studies.

New evidence about HW Vir’s circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling

ABSTRACT The post common-envelope eclipsing binary HW Virginis (HW Vir) has had many circumbinary companions proposed based on eclipse timing variations. Each proposed solution has lacked in predictability and orbital stability, leaving the origin of the eclipse timing variations an active area of research. Leveraging the catalogue of Hipparcos and Gaia proper motion anomalies, we show there is slight evidence for a circumbinary companion orbiting HW Vir. We place an upper limit in mass for such a companion which excludes some previously claimed companions. We also apply this method to V471 Tauri and confirm the non-detection of a previously claimed brown dwarf. We adapt the kima nested sampling code to analyse eclipse timing variations and re-analyse archival data on HW Vir, varying the order of the ephemeris that we fit for and the amount of the data that we use. Although signals are clearly present, we find two signals around 2500 and 4000-d periods that are not coherent between different chunks of the data, so are likely to not be of planetary origin. We analyse the whole data set and find the best solution to contain four signals. Of these four we argue the outermost is the most compatible with astrometry and thus the most likely to be of planetary nature. We posit the other three pseudo-periodic signals are caused by physical processes on the white dwarf. The eventual release of the full Gaia epoch astrometry is a promising way to confirm whether circumbinary planets exist around HW Vir (and other similar systems), and explore white dwarf physics.

Four new compact triply eclipsing triples found with Gaia and TESS

ABSTRACT This paper presents a comprehensive analysis of four triply eclipsing triple star systems, namely TIC 88206187, TIC 14839347, TIC 298714297, and TIC 66893949. The four systems with third-body eclipses were found in the TESS light curves from among a sample of ∼400 matches between known eclipsing binaries and the Gaia DR3 Non-Single Star solution data base. We combined photometric light curves, eclipse timing variations, archival spectral energy distributions, and theoretical evolution tracks in a robust photodynamical analysis to determine the orbital and system parameters. The triples have outer periods of 52.9 d, 85.5 d, 117 d, and 471 d, respectively. All dozen stars have masses ≲ 2.6 M⊙. The systems are quite flat with mutual inclination angles between the inner and outer orbital planes that are all ≲ 4°. The outer mass ratios (q ≡ M3/Mbin) range from 0.39 to 0.76, consistent with our earlier collection of compact triply eclipsing triples. TIC 88206187 exhibits a fractional radius of the outer tertiary component (rB ≡ RB/aout) exceeding 0.1 (only the third such system known), and we consider its future evolution. Finally, we compare our photodynamical analysis results and the orbital parameters given in the Gaia DR3 NSS solutions, indicating decent agreement, but with the photodynamical results being more accurate.

Testing the planetary hypothesis of NY Virginis: anticipated change in the eclipse timing trend within the next five years

ABSTRACT Regarding the recent debate about the potential circumbinary exoplanets around NY Virginis (NY Vir), we analysed mid-eclipse timings of NY Vir using archival photometric data as well as our own observations and the ones from TESS. For this purpose, we first modelled the available eclipse light curves of the binary system to determine the masses of the stars. Then, we measured mid-eclipse times by fitting the light-curve model cycle-to-cycle to the light curves from TESS and our observations. By fitting a Newtonian eclipse timing model to the data, which takes both the light-time effect and potential mutual gravitational interactions into account, we derived orbital parameters and masses of the potential circumbinary planets assuming both eccentric and circular orbits. The models without a quadratic term that can model any possible secular trend, converged to comparable results. Dynamical stability tests show that our Newtonian timing solution corresponds to stable orbital configurations for two circumbinary planets with masses ∼2.3 and ∼4.0 MJup in orbits with very low eccentricity. Our analyses show that the addition of quadratic term for modelling the eclipse timing variation may induce the planetary orbits to be eccentric, hence more likely to be unstable. According to our findings, an upward trend in the eclipse timings followed by a downward one within the next five years is expected due to binary motion induced by circumbinary planets.