Eclipse Times Research Articles

A study of nine compact triply eclipsing triples

ABSTRACTIn this work, we report the independent discovery and analysis of nine new compact triply eclipsing triple star systems found with the Transiting Exoplanet Survey Satellite (TESS) mission: TICs 47151245, 81525800, 99013269, 229785001, 276162169, 280883908, 294803663, 332521671, and 356324779. Each of these nine systems exhibits distinct third-body eclipses where the third (‘tertiary’) star occults the inner eclipsing binary (EB), or vice versa. We utilize a photodynamical analysis of the TESS photometry, archival photometric data, TESS eclipse timing variations of the EBs, available archival spectral energy distribution (SED) curves, and, in some cases, newly acquired radial velocity observations, to solve for the parameters of all three stars, as well as most of the orbital elements. From these analyses we find that the outer orbits of all nine systems are viewed nearly edge on (i.e. within ≲4°), and six of the systems are coplanar to within 5°; the others have mutual inclination angles of 20°, 41°, and possibly 179° (i.e. a retrograde outer orbit). The outer orbital periods range from 47.8 to 604 d, with eccentricities spanning 0.004–0.61. The masses of all 18 EB stars are in the range of 0.9–2.6 M⊙ and are mostly situated near the main sequence. By contrast, the masses and radii of the tertiary stars range from 1.4 to 2.8 M⊙ and 1.5 to 13 R⊙, respectively. We make use of the system parameters from these nine systems, plus those from a comparable number of compact triply eclipsing triples published previously, to gain some statistical insight into their properties.

Reaching Submillisecond Accuracy in Stellar Occultations and Artificial Satellite Tracking

In recent years, there appeared a need for astronomical observations timed with submillisecond accuracy. These include, e.g., timing stellar occultations by small, subkilometer, or fast near-Earth asteroids and tracking artificial satellites in low-Earth orbit using optical sensors. Precise astrometry of fast-moving satellites and accurate timing of stellar occultations have parallel needs, requiring a reliable time source and good knowledge of camera delays. Thus, there is a need for an external device that would enable equipment and camera testing to check if they reach the required accuracy in time. We designed, constructed, and thoroughly tested a New EXposure Timing Analyser (NEXTA), a Global Navigation Satellite System–based precise timer allowing us to reach an accuracy of 0.1 ms, which is an order of magnitude better than in previously available tools. The device is a simple strip of blinking diodes to be imaged with a camera and compare the imaged time with the internal camera time stamp. Our tests spanned a range of scientific cameras widely used for stellar occultations and ground-based satellite tracking. The results revealed high reliability of both NEXTA and most of the tested cameras but also pointed out that practically all cameras had internal time biases of various levels. NEXTA can serve the community, being easily reproducible with inexpensive components. We provide all the necessary schemes and usage instructions.

The Evolution of the Supersoft X-Ray Source WX Cen Dominated by Magnetic Wind

WX Cen is most likely one of the Galactic counterparts of compact binary supersoft X-ray sources as a member of the V Sagittae class, in which mass is transferred from a donor secondary to a massive white dwarf primary via an accretion disk. Based on the photometric observations from the TESS space telescope and AAVSO database, 218 times of light minimum were determined. By collecting all available eclipse timings of WX Cen from the literature together with those newly determined, we constructed an O−C diagram and analyzed the variations in the orbital period of the eclipsing binary. It is confirmed that the orbital period is continuously decreasing and the rate of the change in the orbital period is revised to . The mass of the donor secondary is estimated as M s ∼ 0.6 M ⊙, when the white dwarf mass is M WD ∼ 0.9 M ⊙. By considering a conservative mass transfer from the secondary to the primary, the orbital period of WX Cen should be increasing, which is opposite to the observed continuous decrease. Therefore, the decrease in the period can be plausibly explained as the result of angular momentum loss (AML) via magnetic wind from the secondary and/or from the accretion disk. The AML causes the donor secondary with a low mass to continually be filling its critical Roche lobe and transferring material to the white dwarf. In this way, the evolution of WX Cen is dominated by the magnetic wind and continuously radiating supersoft X-rays.

V994 Herculis: a unique triply eclipsing sextuple star system

ABSTRACTWe report the discovery with the Transiting Exoplanet Survey Satellite (TESS) of a third set of eclipses from V994 Herculis (V994 Her, TIC 424508303), previously only known as a doubly eclipsing system. The key implication of this discovery and our analyses is that V994 Her is the second fully characterized (2+2) + 2 sextuple system, in which all three binaries eclipse. In this work, we use a combination of ground-based observations and TESS data to analyse the eclipses of binaries A and B in order to update the parameters of the inner quadruple’s orbit (with a derived period of 1062 ± 2 d). The eclipses of binary C that were detected in the TESS data were also found in older ground-based observations, as well as in more recently obtained observations. The eclipse timing variations of all three pairs were studied in order to detect the mutual perturbations of their constituent stars, as well as those of the inner pairs in the (2 + 2) core. At the longest periods they arise from apsidal motion, which may help constraining parameters of the component stars’ internal structure. We also discuss the relative proximity of the periods of binaries A and B to a 3:2 mean motion resonance. This work represents a step forward in the development of techniques to better understand and characterize multiple star systems, especially those with multiple eclipsing components.

Eclipse Timing Variations Observed in PCEB Systems

Post-common Envelope Eclipsing Binary (PCEB) systems with a white or sub-dwarf primary and a low-mass secondary are ideal systems to study Eclipse Timing Variations (ETVs) due to their relatively small total masses which make it easy to detect gravitationally bound, yet unseen, additional bodies even within planetary limits on long-period orbits. With the addition of the recent discovery of two planetary-mass bodies in the sdB + dM binary Kepler-451 system, the number of circumbinary planets in PCEBs approaches 30 now. However, some of these systems turned out to be dynamically unstable with the suggested planetary parameters. As more observations accumulate over time, there have been significant changes in both the number of suggested planets and their parameters. These necessitate a look back to the ETV analyses of these systems with new and more precise data spanning longer baselines. Within this contribution, we review the systems hosting substellar bodies suggested from the light-time effect they are claimed to be causing. We list the general problems encountered during the ETV analyses and the interpretation of the results, and comment on their possible solutions. We calculate and present the potentials of supporting evidence from astrometry, radial velocity, and transit observations as well as tests through dynamical stability analyses and magnetic activity assumptions.

Apsidal motion and absolute parameters of GV Nor and V881 Sco based on mid-resolution spectroscopy and TESS photometry

ABSTRACT The veracity of stellar evolution models and theoretical internal structure constants may be subjected to stringent tests by using physical parameters obtained from spectroscopic and photometric observations of eclipsing binary systems that exhibit apsidal motion. Two eclipsing binary stars from the southern hemisphere with no prior published spectroscopic analyses were selected for this study: GV Nor and V881 Sco. Spectroscopic observations of these two eccentric binary systems were made at the South African Astronomical Observatory (SAAO) in 2018 and 2019, and their mid-resolution spectra were obtained. The radial velocities were measured using the cross-correlation method as well as by disentangling the spectra. The rotational broadening of the disentangled spectra of the components was also determined. The absolute parameters of these two systems were obtained by analyzing the SAAO-based spectroscopic data in conjunction with photometric data from Transiting Exoplanet Survey Satellite. Apsidal motion parameters for these two eccentric binary systems were calculated by analysing eclipse timing variations. Granada and Padova evolution models indicated ages of 340 ± 35 Myr for GV Nor and 760 ± 15 Myr for V881 Sco, in agreement with the observational results. The theoretical internal structure constants estimated from the Granada models were compatible with the observational values within the error limits. However, for both systems, it was found that their circularization and synchronization timescales were shorter than their respective evolutionary ages. Therefore, the fact that the components rotate faster than their synchronized values and still have rather large eccentric orbits (e ∼ 0.11) challenges present theories of circularization and spin–orbit synchronization.

OBSERVATION OF AN OCCULTATION OF THE UCAC4 488-082551 STAR BY ASTEROID (76228) 2000 EH 75 ON 31 MAY 2022

Observations of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 were carried out on 31 May 2022 at Kryzhanivka observation station of Odesa I. I. Mechnykov National University (the observatory code A85). A set of instruments, which included a Schmidt telescope (the primary mirror diameter D = 271.25 mm; the corrector plate diameter D k = 223.9 mm; the focal length F = 440 mm), a GPS receiver and Videoscan-415-2001 CCD camera, was used to perform observations. The observing conditions were as follows: clear sky, the star’s altitude 49 0 south, the Moon was below the local horizon. The target star from the UCAC4 catalogue (Zacharias et al. 2013) has the following photometric parameters: m B = 14.008; m V = 12.720; m r = 12.284; m i = 11.813. The diameter of the star has not been determined. Asteroid (76228) is a Main Belt asteroid with an orbital period of 4.17178 years. It has an absolute magnitude of 14.93, the visible geometric albedo of 0.123±0.013 and diameter of 5.00±0.23 km (Masiero et al. 2011). The time of occultation predicted using ephemerides was 23:52:44±4 sec. The maximum duration of the occultation was 0.4 sec, provided that the observing site was located at the centre of the occultation track (strip). A drop in the star’s brightness observed during occultation was about 8 m . The occultation event was recorded as a sequence of GIF images with the exposure time of 0.5 sec per frame. The system clock of the computer used for the occultation recording was controlled with a GPS receiver in a fashion similar to that described in the paper by Karbovsky et al. (2017). The data processing yielded an estimate of the occultation duration of 0.46±0.04 sec. The uncertainty of the occultation start time within exposure results in the total estimate of accuracy in timing the maximum phase of occultation 23:52:44.06±0.10 sec. The chord length across the asteroid estimated by timing the occultation is L = 9.2±0.8. This chord length is close to the estimates of the asteroid diameter reported in the paper by Masiero et al. (2011).

KIC 7955301: A hierarchical triple system with eclipse timing variations and an oscillating red giant

KIC 7955301 is a hierarchical triple system with clear eclipse timing and depth variations that was discovered by the Kepler satellite during its original mission. It is composed of a non-eclipsing primary star at the bottom of the red giant branch (RGB) on a 209-day orbit with a K/G-type main-sequence (MS) inner eclipsing binary (EB), orbiting in 15.3 days. This system was noted for the large amplitude of its eclipse timing variations (ETVs, over 4 h), and the detection of clear solar-like oscillations of the red-giant (RG) component, including p-modes of degree up to l = 3 and mixed l = 1 modes. The system is a single-lined spectroscopic triple, meaning that only spectral lines from the RG are detected. We performed a dynamical model by combining the 4-year-long Kepler photometric data, ETVs, and radial-velocity data obtained with the high-resolution spectrometers ARCES, of the 3.5 m ARC telescope at Apache Point observatory, and SOPHIE, of the 1.93 m telescope at Haute-Provence Observatory. The “dynamical” mass of the RG component was determined with a 2% precision at 1.30−0.02+0.03 M⊙. We performed asteroseismic modeling based on the global seismic parameters and on the individual frequencies. Both methods provide an estimate of the mass of the RG that matches the dynamical mass within the uncertainties. Asteroseismology also revealed the rotation rate of the core (≈15 days), the envelope (∼150 days), and the inclination (∼75°) of the RG. Three different approaches led to an estimation of the age between 3.3 and 5.8 Gyr, which highlights the difficulty of determining stellar ages despite the exceptional wealth of information available for this system. On short timescales, the inner binary exhibits eclipses with varying depths during a 7.3-year long interval, and no eclipses during the consecutive 11.9 years. This is why Kepler could detect its eclipses but TESS cannot, and the future ESA PLATO mission should detect these. In the long term, the system appears to be stable and owes its evolution to the evolution of its individual components. This triple system could end its current smooth evolution by merging by the end of the RGB of the primary star because the periastron distance is ≈142 R⊙, which is close to the expected radius of the RG at the tip of the RGB.

Light and Period Variations in Two K-type Contact Binaries: HI Leo and V523 Cas

We presented a low-precision spectrum for HI Leo, Transiting Exoplanet Survey Satellite data for V523 Cas, and new photometry for both K-type contact binaries. Comparing their light curves on different observing dates, we found small intrinsic variabilities, such as variable amplitudes for HI Leo and the varying heights around the second maxima for V523 Cas. By the Wilson–Devinney Code, we deduced six photometric solutions. The dark spot of V523 Cas may appear on the surface of the more massive component on BJD 2458768, while it disappears on BJD 2458779. Our results indicate that the two binaries are W-type shallow-contact binaries (f ≤ 10%). From the eclipse timing residuals, we found that the orbital periods may continuously increase, accompanied by one to two light-time effects due to additional bodies. The modulated periods and semi-amplitudes are P 3 = 25.8(±1.0) yr and A 3 = 0.ͩ0066(6) for HI Leo, P 3 = 114.8(±2.0) yr and A 3 = 0.ͩ0448(12), P 4 = 18.89(±0.14) yr and A 4 = 0.ͩ0025(2) for V523 Cas, respectively. The orbital period secularly increases at a rate of dP/dt = 2.86(±0.11) × 10−7 day yr−1 for HI Leo and dP/dt = 3.45(±0.07) × 10−8 day yr−1 for V523 Cas, which may be attributed to mass transfer from the secondary to the primary. With mass transferring, the shallow-contact binaries, HI Leo and V523 Cas, will evolve into the broken-contact configurations.

HT Lyn and IR Lyn: Two Semi-detached-type Near-contact Binaries with Stable Orbital Period

We presented the first photometric and orbital period investigations for two near-contact binaries: HT Lyn and IR Lyn. The light-curves solutions derived from both our ground-based and various surveys’ observations suggested that HT Lyn and IR Lyn are two semi-detached-type near-contact binaries with the secondary and primary components filling the Roche lobe. Combining the eclipse timings derived from several surveys’ data and our observations with those reported in the literature, we modified the orbital periods and revealed that their orbital periods were stable for the last two decades. The absolute physical parameters were well determined by using the empirical relations and the Gaia-distance-based method. Similar to other near-contact binaries, the primary components of HT Lyn and IR Lyn are evolving at the main-sequence stage, while their less-massive secondary components show the over-sized and over-luminosity features and should be more evolved than their primary ones. Combining the stable orbital period with the semi-detached configurations, we infer that the two near-contact binaries may be just located in the critical phase and evolving from the current semi-detached phase to the detached or contact one.

Influence of chronometer error uncertainties on the Longitude of Shackleton's vessel, Endurance

AbstractIn 1915 while the Imperial Trans-Antarctic Expedition's vessel Endurance was icebound in the Weddell Sea, lunar occultation timings were carried out in order to rate the chronometers and thereby find longitude. The original observations have been re-analysed using modern lunar ephemerides and catalogues of star positions. The times derived in this way are found to differ by an average of 20 s from those obtained during the expedition using positions given from the Nautical Almanac and introduces an additional offset of the true positions to the east of those recorded in the log.

A Photometric and Spectroscopic Study of the Short-period Algol EW Boötis with a δ Sct Pulsator

In this paper, we present Transiting Exoplanet Survey Satellite (TESS) photometry and high-resolution spectra of the short-period Algol EW Boo. We obtained double-lined radial velocities (RVs) from the time-series spectra and measured the effective temperature of the primary star as T eff,1 = 8560 ± 118 K. For the orbital period study, we collected all times of minima available for over the last 30 yr. It was found that the eclipse timing variation of the system could be represented by a periodic oscillation of 17.6 ± 0.3 yr with a semiamplitude of 0.0041 ± 0.0001 day. The orbital and physical parameters were derived by simultaneously analyzing the TESS light and RV curves using the Wilson–Devinney (WD) binary star modeling code. The component masses and radii were showed over 3% precision: M 1 = 2.67 ± 0.08 M ⊙, M 2 = 0.43 ± 0.01 M ⊙, R 1 = 2.01 ± 0.02 R ⊙, and R 2 = 1.35 ± 0.01 R ⊙. Furthermore, multiple frequency analyses were performed for the light-curve residuals from the WD model. As a result, we detected 17 pressure-mode pulsations in the region of 40.15–52.37 day−1. The absolute dimensions and pulsation characteristics showed that the δ Sct pulsator was the more massive and hotter primary star of the EW Boo.

Orbital stability of proposed NY virginis exoplanets

ABSTRACT Er et al. (2021) recently proposed a two-planet solution to account for eclipse timing variations (ETVs) observed from the sdB binary NY Virginis. We tested the proposed planetary system for orbit stability using both numerical simulations and chaotic behaviour analysis. The best-fit orbits, as well as those with parameters varying by the published uncertainty range in each parameter, were unstable on a time-scale much less than the presumed lifetime of the PCEB phase (∼100 Myr). Suggesting that the proposed circumbinary companions fail to provide a complete explanation for the observed ETVs.

Utilizing a Global Network of Telescopes to Update the Ephemeris for the Highly Eccentric Planet HD 80606 b and to Ensure the Efficient Scheduling of JWST

The transiting planet HD 80606 b undergoes a 1000 fold increase in insolation during its 111 days orbit due to it being highly eccentric (e = 0.93). The planet’s effective temperature increases from 400 to over 1400 K in a few hours as it makes a rapid passage to within 0.03 au of its host star during periapsis. Spectroscopic observations during the eclipse (which is conveniently oriented a few hours before periapsis) of HD 80606 b with the James Webb Space Telescope (JWST) are poised to exploit this highly variable environment to study a wide variety of atmospheric properties, including composition, chemical and dynamical timescales, and large scale atmospheric motions. Critical to planning and interpreting these observations is an accurate knowledge of the planet’s orbit. We report on observations of two full-transit events: 2020 February 7 as observed by the TESS spacecraft and 2021 December 7–8 as observed with a worldwide network of small telescopes. We also report new radial velocity observations which, when analyzed with a coupled model to the transits, greatly improves the planet’s orbital ephemeris. Our new orbit solution reduces the uncertainty in the transit and eclipse timing of the JWST era from tens of minutes to a few minutes. When combined with the planned JWST observations, this new precision may be adequate to look for non-Keplerian effects in the orbit of HD 80606 b.

Variability of eclipse timing: the case of V471 Tauri

ABSTRACT The post-common envelope binary V471 Tauri has been an object of interest for decades. V471 Tau shows various phenomena due to its evolutionary state and unique properties, e.g. its magnetic accretion and eclipse timing variation (ETV). Previous authors explained the ETVs by different sometimes contradictory theories. In this paper, we present and analyse the variability of the eclipse timing of this star. We observed V471 Tauri over the last 10 yr and covered the second cycle of its period variation. Based on our analysis of the presented data, we assess the possible existence of a brown dwarf in this system and derive its orbital parameters. We compare the results of our dynamical modelling to the solution predicted by Applegate-mechanism theories, which have been developed in recent studies. We found that the observed ETV cannot be explained only by the presence of additional components to the binary.

TIC 114936199: A Quadruple Star System with a 12 Day Outer-orbit Eclipse

We report the discovery with TESS of a remarkable quadruple star system with a 2+1+1 configuration. The two unique characteristics of this system are that (i) the inner eclipsing binary (stars Aa and Ab) eclipses the star in the outermost orbit (star C), and (ii) these outer fourth-body eclipses last for ∼12 days, the longest of any such system known. The three orbital periods are ∼3.3 days, ∼51 days, and ∼2100 days. The extremely long duration of the outer eclipses is due to the fact that star B slows binary A down on the sky relative to star C. We combine TESS photometric data, ground-based photometric observations, eclipse timing points, radial velocity measurements, the composite spectral energy distribution, and stellar isochrones in a spectrophotodynamical analysis to deduce all of the basic properties of the four stars (mass, radius, T eff, and age), as well as the orbital parameters for all three orbits. The four masses are M Aa = 0.382 M ⊙, M Ab = 0.300 M ⊙, M B = 0.540 M ⊙, and M C = 0.615 M ⊙, with a typical uncertainty of 0.015 M ⊙.

Eclipse Timings of the LMXB XTE J1710−281 : discovery of a third orbital period glitch

ABSTRACT We present an updated measurement of orbital period evolution of LMXB XTE J1710−281 by using eclipse timing technique. Using data obtained with XMM-Newton, Suzaku, RXTE, Chandra, and AstroSat observatories, we report 21 new measurements of X-ray mid-eclipse times. We have discovered a third orbital period glitch in XTE J1710−281 with an F-test false alarm probability of ∼0.7 per cent for occurrence of the third glitch and report detection of four distinct epochs of orbital period in this system. This work presents a more robust estimation of occurrence of the second orbital period glitch. However, the epoch of occurrence of the third glitch is poorly constrained, between MJD 55726 and 56402. We have put lower limits of 1.48, 0.97, and 0.45 ms, on sudden changes in orbital period between the successive epochs. We discuss the implications of our findings in context of magnetic nature of the companion star and possible scattering events with circumbinary objects around this binary system.

Towards a consistent model of the hot quadruple system HD 93206 = QZ Carinæ

Aims.HD 93206 is a massive early-type stellar system composed of components resolved by direct imaging (Ab, Ad, B, C, D) and a compact subsystem (Aa1, Aa2, Ac1, Ac2). Its geometry was already determined on the basis of extensive photometric, spectroscopic, and interferometric observations. However, the fundamental absolute parameters are still not known precisely enough.Methods.We use an advancedN-body model to account for all mutual gravitational perturbations among the four close components, and all observational data types, including astrometry, radial velocities, eclipse timing variations, squared visibilities, closure phases, triple products, normalized spectra, and spectral energy distribution (SED). The model has 38 free parameters, grouped into three sets of orbital elements, component masses, and their basic radiative properties (T, logg,vrot).Results.We revised the fundamental parameters of QZ Car as follows. For a model with the nominal extinction coefficientRV ≡ AV/E(B − V) = 3.1, the best-fit masses arem1 = 26.1 MS,m2 = 32.3 MS,m3 = 70.3 MS, andm4 = 8.8 MS, with uncertainties of the order of 2 MS, and the system distanced = (2800 ± 100) pc. In an alternative model, where we increased the weights of the radial velocity (RV) and transit timing variation (VTT) observations and relaxed the SED constraints, because extinction can be anomalous withRV ∼ 3.4, the distance is smaller:d = (2450 ± 100) pc. This corresponds to the distance of the Collinder 228 cluster. Independently, this is confirmed by dereddening the SED, which is only then consistent with the early-type classification (O9.7Ib for Aa1, O8III for Ac1). Future modelling should also account for an accretion disk around the Ac2 component.

CoRoT-TESS eclipsing binaries with light-travel-time effect

ABSTRACT Identifying long-period eclipsing binaries with space-based photometry is still a challenge even in the century of space telescopes due to the relatively short observation sequences and short lifetime of these missions. The Transiting Exoplanet Survey Satellite (TESS) space telescope is an appropriate tool to supplement previous space-based observations. In this paper, we report the first results of the eclipse timing variation (ETV) analyses of eclipsing binaries (EBs) measured by CoRoT and TESS space telescopes. Among the 1428 EB candidates we found four new potential triple candidates, for which ETV was analysed and fitted by the well-known light-travel-time effect (LTTE). One of them shows significant phase shift in its folded light curve which required extra care. In this paper, we also present some other systems showing significant ETV signals that could be explained by mass transfer or apsidal motion.

The recurrent nova U Scorpii from the 2010.1 to 2022.4 eruptions; the missed eruption of 2016.78 ± 0.10 and the critical complex period changes

ABSTRACT U Sco is a recurrent nova with 11 observed eruptions, most recently in 2010.1 and 2022.4. I report on my program (running since 1989) of measuring eclipse times and brightnesses of U Sco in quiescence, from 2010 to 2022. The orbital period suddenly increased by +22.4 ± 1.0 parts-per-million across the 2010.1 eruption. This period change is greater than the near-zero period change (+3.9 ± 6.1 parts-per-million) across the 1999.2 eruption. This period change cannot come from any of the usual mechanisms, whereas the one remaining possibility is that the period changes are dominated by the little-known mechanism of the nova ejecting asymmetric shells. From 2010.1 to 2016.78, the O − C curve showed a steady period change that was large, with $\dot{P}$ = (−21.0 ± 3.2) × 10−9. This is greatly higher than the steady period changes in the two previous inter-eruption intervals (−3.2 ± 1.9 and −1.1 ± 1.1 × 10−9). This large, variable, and negative $\dot{P}$ apparently comes from magnetic braking of the companion star’s rotation. Starting in 2016.9 ± 0.6, the O − C curve showed a strong kink that is a unique characteristic of the sudden period change (+35.4 ± 7.1 parts-per-million) across a nova event. The brightness in quiescence after 2010.4 shows that the white dwarf accreted the trigger mass for the next nova event in the year 2017.1 ± 0.6. Photometric records show the only possible time for the eruption to peak (such that its total duration of 60 d was undetectable by any observation) is during a 75-d interval inside the 2016 solar gap, thus constraining the missed eruption to 2016.78 ± 0.10.