Light-time Effect Research Articles

OO Leo: An Active Contact Binary with Possible Solar-like Differential Rotation

With Transiting Exoplanet Survey Satellite (TESS) high-precision photometry and Large Sky Area Multi-object Fiber Spectroscopic Telescope medium-resolution spectra, we present the first light and radial velocity curve analyses for the eclipsing binary OO Leo. The simultaneous solution suggests that OO Leo is a W-subtype contact binary with a relatively low mass ratio (1/q = 0.173) and a moderate degree of contact (f = 28.1%). The asymmetry and continuous changes observed in the TESS light curve were properly modeled by one retrograde cool spot on its secondary surface. A detailed investigation of the Hα line also confirmed that the secondary star had a high level of magnetic activity. The retrograde longitudinal motion of the spot can be explained by a solar-like differential rotation in the secondary component. The orbital period investigation revealed that OO Leo is undergoing a secular decrease and a cyclic variation in its orbital period. The secular decrease may be mainly caused by mass transfer from the more massive secondary star to the less massive primary star. The cyclic period variation can be explained by the light–time effect of an invisible third body or the cyclic magnetic activity of the secondary star. The long-lived spot migration in the longitudinal direction makes OO Leo an excellent target for investigating the differential rotations of contact binaries.

Autonomous Vision-Based Algorithm for Interplanetary Navigation

The surge of deep-space probes makes it unsustainable to navigate them with standard radiometric tracking. Autonomous interplanetary satellites represent a solution to this problem. In this work, a vision-based navigation algorithm is built by combining an orbit determination method with an image processing pipeline suitable for interplanetary transfers of autonomous platforms. To increase the computational efficiency of the algorithm, an extended Kalman filter is selected as state estimator, fed by the positions of the planets extracted from deep-space images. An enhancement of the estimation accuracy is performed by applying an optimal strategy to select the best pair of planets to track. Moreover, a novel analytical measurement model for deep-space navigation is developed providing a first-order approximation of the light-aberration and light-time effects. Algorithm performance is tested on a high-fidelity, Earth–Mars interplanetary transfer, showing the algorithm applicability for deep-space navigation.

TESS light curve modeling and period study of four eclipsing binaries

Abstract We reported the light curves and orbital period variations of four short-period eclipsing binaries in the Southern Hemisphere. From short-cadence time-series observations of the TESS, the intrinsic light changes rapidly with time. Δmmax and Δmmin exhibit random wave-like variations or quasi-periodicities. We deduced 14 sets of photometric solutions from the truncated light curves using the W-D program. The results imply that V757 Cen and BC Gru are near-contact binaries, whose one or two components almost fill the Roche lobes with $f>98{{\%}}$. Meanwhile, V535 Ara and AQ Tuc are A-subtype contact binaries. The asymmetric light curves were modelled by a cool spot assumed on a more massive component, which was used to track the stellar longitudes of starspots. Based on all available eclipsing times (ETs), including 1495 ones from TESS light curves (LCs), the orbital period variations of four binaries were analysed. The (O − C) curves are coincidentally demonstrated by the light-time effect (LITE) via the presence of the third bodies. The modulation periods approximate to 50 ∼ 60 years. In the coplanar orbit with the central binaries, the third companions’ masses are 0.105 M⊙ for V757 Cen, 0.340 M⊙ for BC Gru, 0.238 M⊙ for V535 Ara, and 0.343 M⊙ for AQ Tuc, whose systems are stable according to Harrington’s criterion. Therefore, the four short-period eclipsing binaries, V757 Cen, BC Gru, V535 Ara and AQ Tuc are hierarchical triple stellar systems.

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.

The Apparent Tidal Decay of WASP-4 b Can Be Explained by the Rømer Effect

Tidal orbital decay plays a vital role in the evolution of hot Jupiter systems. As of now, this has only been observationally confirmed for the WASP-12 system. There are a few other candidates, including WASP-4 b, but no conclusive result could be obtained for these systems as of yet. In this study, we present an analysis of new TESS data of WASP-4 b together with archival data, taking the light–time effect (LTE) induced by the second planetary companion into account as well. We make use of three different Markov chain Monte Carlo models: a circular orbit with a constant orbital period, a circular orbit with a decaying orbit, and an elliptical orbit with apsidal precession. This analysis is repeated for four cases. The first case features no LTE correction, with the remaining three cases featuring three different timing correction approaches because of the large uncertainties of the ephemeris of planet c. Comparison of these models yields no conclusive answer to the cause of WASP-4 b’s apparent transit timing variations. A broad range of values of the orbital decay and apsidal precession parameters are possible, depending on the LTE correction. However, the LTE caused by planet c can explain on its own—in full—the observed transit timing variations of planet b, with no orbital decay or apsidal precession being required at all. This work highlights the importance of continued photometric and spectroscopic monitoring of hot Jupiters.

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.

Orbital Period Variations of the Eclipsing Binaries RX Ari and V449 Oph

The variations in the orbital period of the eclipsing binaries RX Ari and V449 Oph have been analyzed. It has been shown that the variations in the period of RX Ari can be represented by a superposition of a secular period increase and two cyclic variations. The secular increase in the period can be explained by the exchange of matter between the components. Cyclic variations in the period may be due to the presence of two additional bodies in the system, or only one additional body in combination with the magnetic activity of the main component. The variations in the orbital period of V449 Oph can be represented with almost equal accuracy either as a superposition of two cyclic variations, or as a superposition of a secular period increase and two cyclic variations. The obtained parameters of the light-time effects and magnetic quantities lead to the conclusion that it is preferable to use linear elements to represent the variations in the orbital period of V449 Oph. In this case, one of the cyclic variations can be a consequence of the light-time effect, and the second one can be a consequence of the magnetic activity of the secondary component. Both types of variations can also be a consequence of the magnetic activity of the secondary component.

Synthetic Light Curve Design for Pulsating Binary Stars to Compare the Efficiency in the Detection of Periodicities

B supergiant stars pulsate in regular and quasi-regular oscillations resulting in intricate light variations that might conceal their binary nature. To discuss possible observational bias in a light curve, we performed a simulation design of a binary star affected by sinusoidal functions emulating pulsation phenomena. The Period04 tool and the WaveletComp package of R were used for this purpose. Thirty-two models were analysed based on a combination of two values on each of the k = 6 variables, such as multiple pulsations, the amplitude of the pulsation, the pulsation frequency, the beating phenomenon, the light-time effect, and regular or quasi-regular periods. These synthetic models, unlike others, consider an ARMA (1, 1) statistical noise, irregular sampling, and a gap of about 4 days. Comparing Morlet wavelet with Fourier methods, we observed that the orbital period and its harmonics were well detected in most cases. Although the Fourier method provided more accurate period detection, the wavelet analysis found it more times. Periods seen with the wavelet method have a shift due to the slightly irregular time scale used. The pulsation period hitting rate depends on the wave amplitude and frequency with respect to eclipse depth and orbital period. None of the methods was able to distinguish accurate periods leading to a beating phenomenon when they were longer than the orbital period, resulting, in both cases, in an intermediate value. When the beating period was shorter, the Fourier analysis found it in all cases except for unsolved quasi-regular periods. Overall, the Morlet wavelet analysis performance was lower than the Fourier analysis. Considering the strengths and disadvantages found in these methods, we recommend using at least two diagnosis tools for a detailed time series data analysis to obtain confident results. Moreover, a fine-tuning of trial periods by applying phase diagrams would be helpful for recovering accurate values. The combined analysis could reduce observational bias in searching binaries using photometric techniques.

The Exo-Jupiter Candidate FL Lyr b in Data of Kepler and TESS Space Missions

We study the light-time effect in the eclipsing binary system FL Lyr using data of the Kepler and TESS space missions. We demonstrate that the system contains a candidate exo-Jupiter FL Lyr b, its probable orbital period being about 22 years.

PHOTOMETRIC ANALYSIS OF ECLIPSING BINARIES: VY UMI, RU UMI AND GSC 04364-00648

We present the photometric analysis of BVR and TESS light curves of three eclipsing binaries, together with their period changes considering archival data and new minima times from our and TESS observations. For the first time we detected wave-like variations with low-amplitude in O − C residua of RU UMi, which can be interpreted as a consequence of the light-time effect caused by the 3rd component with period 7370 days. The period increase detected in the VY UMi system corresponds to mass transfer from the secondary to the primary component. For the GSC 04364-00648 binary system we find quadratic changes on the O − C diagram, which correspond to a period decrease. We cannot make assumptions about their nature, mainly due to short time of observation and uneven coverage of O − C diagram. We also determined the absolute parameter of their components using the photometric solution and GAIA distances.

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.

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.

Chromospheric activity and period variations of the contact binary EE Cet from TESS

From the 100-day TESS observations, we comprehensively studied the variations of the light curve and orbital period for EE Cet. It is found that an 83.2-day oscillation occurs in the differences between two light maxima, which identifies the existence of chromospheric activity. Using the 2016-version Wilson–Devinney code, we obtained three sets of photometric solutions from TIC1432, TIC2449 and TIC2495. Results imply a dark spot immigrating from longitude 217.9(±2.2)∘ in BJD 2459449 into longitude 61.6(±0.7)∘ in BJD 2459495. From the eclipse timing residuals (i.e., observed minus computed), the orbital period of EE Cet may be undergoing a long-term period increase with a periodic variation. The 15.95-yr periodic oscillation with A=0.0038(1) d may result from the light-time effect due to the third body. Meanwhile, the orbital period increases at a rate of dP/dt=1.74(±0.02)×10−7dyr−1, which may result from the conserved mass transfer from the less massive component to the more massive one. With mass transferring, EE Cet will evolve into the broken-contact configuration, as predicted by the TRO theory.

44 Boo – A unified integrated light curve analysis

Radial velocity (RV) data from Lu et al. (2001) were combined with light curve (LC) data from the Transiting Exoplanet Survey Satellite (TESS) in an integrated Wilson-Devinney analysis to yield fundamental parameters. Obtained were masses M 1 = 0.526 (5), M ʘ, and M 2 = 1.063 (7) M ʘ, stellar radii R1 = 0.65 (2) Rʘ, and R2 = 0.90 (1) Rʘ, and luminosities L1 = 0.40 (4) Lʘ and L2 = 0.62 (5) Lʘ. These are in reasonable agreement with the values from Hill et al. (1989). Additional analyses were carried out also using the same RV data but substituting, in turn, the LC datasets of Binnendijk (1955), Duerbeck (1978), Robb and Milone (1982) and Genet et al. (1982). While the four Earthbound LC datasets were of much lower precision than the satellite data, they still yielded reasonable agreement in the final parameters. Additionally, they yielded some insight as to the behaviour of the dark spot (on star 1) over some 75 years. The B and V light curve data of Duerbeck (1978) suggested that the unresolved companion is hot. An updated period study originally presented in Nelson et al. (2014) but now with a Light Time Effect (LiTE) fit is presented. Fifteen new times of minimum from the TESS data were added, requiring only a modest refinement of the LiTE parameters. The intrinsic rate of period change (that is, with the LiTE component removed) is dP/dt = 1.80 (20) x 10−7 seconds/year. If dP/dt can be attributed to conservative mass exchange, the rate would be dM1/dt = -2.33 (26) x 10−7 Mʘ/year. When the fundamental parameters for each star were added to the Log L vs Log T plot for EW-type binaries from Yakut and Eggleton (2005), the results suggested that star 1 of the W-type binary is under-luminous, while the cooler but larger secondary is somewhat evolved. Both are in a marginal contact, typical of W-type eclipsing binaries.

Light-Time Effect in the Orbital Period Variations of the Eclipsing Binaries TT Del, EU Hya, and SV Tau

Light-Time Effect in the Orbital Period Variations of the Eclipsing Binaries TT Del, EU Hya, and SV Tau

Orbital Period Changes of Selected Two Semi-Deteached Binaries

Since the data obtained from satellite data are very sensitive, the minima times of the target systems have obtained from Kepler (K2) and TESS observations. A total of 14 minima times were obtained from Kepler (K2) data for the AF Gem system and 11 minima times in two different sectors from the TESS data for the RY Gem system. In this study, orbital period behaviors of semi-detached binaries (SDBs) AF Gem and RY Gem systems have investigated, together with minima times obtained from literature and satellite data. It has been observed that the orbital periods of AF Gem and RY Gem decrease. The period change rates of AF Gem and RY Gem systems are determined as -4.1×10-8 and -6.5×10-6 day/ year. The magnetic activity of the cooler components of the systems may be the reason for the periods decrease, and therefore the mass loss rates of the systems have calculated. For AF Gem and RY Gem, mass loss rate was found to be -4.4×10-8 M⊙/year and -8.2×10-7 M⊙/year, respectively. In the O-C graph of AF Gem, sinüsoidal variations also exist. Sinusoidal change may be demonstrated as being the result of a light time effect (LITE) via a tertiary body around the eclipsing pair. The minimum mass of probable third star around AF Gem has found to be 0.24 M⊙.

Onboard Orbit Determination for Deep-Space CubeSats

In this work, an orbit determination algorithm suitable for CubeSats onboard implementation is developed, which simulates optical autonomous navigation accomplished by a stand-alone platform. An extended Kalman filter featuring line-of-sight acquisitions of planets is selected as the state estimator, and its performances are tested on a Raspberry Pi, whose characteristics are comparable to a miniaturized onboard computer. An improvement of the solution accuracy is performed by correcting the planetary light-time and aberration effects as well as by exploiting the optimal beacons selection strategy to acquire the external observations. Moreover, the numerical precision of the estimator is improved through the implementation of factorization techniques and nondimensionalization strategies. The results are presented for a sample Earth–Mars transfer, where the time slot for the navigation campaign involves 2 h every 10 days. At final time, the probe position and velocity are estimated with a accuracy of 360 km and 0.04 m/s, respectively.

V0644 Ser: An Active Ultrashort Period Contact Binary Star

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

First photometric and orbital period investigations of four W UMa-type eclipse binaries

AbstractWe presented the first photometric and orbital period investigations for four W Ursae Majoris-type binaries: V473 And, V805 And, LQ Com, and EG CVn. The photometric solutions suggested that V805 And and LQ Com are two total-eclipse contact binaries, while V473 And and EG CVn are partial-eclipse ones. V473 And and LQ Com belong to the A-subtype contact binaries, while V805 And and EG CVn belong to the W subtype. The O’Connell effects found in the light curves of V805 And, LQ Com, and EG CVn can be interpreted as a result of a cool spot on the surface of their less massive and hotter primary components. Based on two different methods, the absolute physical parameters were properly determined. Combining the eclipse timings derived from our observations and survey’s data with those collected from literature, we investigated their orbital period variations. The results show that the orbital periods of V473 And, V805 And, and EG CVn are undergoing a secular decrease/increase superposed a periodic variation, while LQ Com exhibits a possible cyclic period variation with a small amplitude. The secular period changes are caused mainly by the mass transfer between two components, while the cyclic period oscillations may be interpreted as the results of either the light-time effect due to the third body or the cyclic magnetic activity. Finally, we made a statistical investigation for nearly 200 contact binaries with reliable physical parameters. The statistical results suggested that the W-subtype systems are more evolved than the A-subtype ones. Furthermore, the evolutionary direction of A-subtype into W-subtype systems is also discussed. The opposite evolutionary direction seems to be unlikely because it requires an increase of the total mass, the orbital angular momentum, and the temperature differences between two components of a binary system.

Pharmacokinetics and tissue distribution characteristics of the novel photosensitizer 32-(4-methoxyphenyl)-152-aspartyl-chlorin e6

二氢卟吩类衍生物32-(4-甲氧基苯基)-152-天冬氨酸-二氢卟吩e6(DYSP-C34)是从程海湖螺旋藻中提取并合成的新型光敏剂。研究DYSP-C34在生物体内的药代动力学及组织分布过程对光动力疗法(PDT)的有效性和安全性至关重要。该文运用高效液相色谱-紫外(HPLC-UV)检测技术,建立了大鼠血浆中DYSP-C34的检测方法。采用沉淀蛋白-液液萃取法处理血浆和组织样品,采用Unitary C18色谱柱(250 mm×4.6 mm, 5 μm)分离,流动相为甲醇-5 mmol/L四丁基磷酸氢铵缓冲盐溶液(70:30, v/v),流速为1.0 mL/min,进样量为20 μL,检测波长为400 nm,柱温为40 ℃。实验结果表明,大鼠血浆药物质量浓度在1~200 μg/mL范围内线性良好,判定系数(r2)为0.9941。在低、中、高(8、40、120 μg/mL)3个添加水平下的提取回收率分别为74.39%、69.71%和65.89%,日内和日间相对标准偏差(RSD)均在5%以内。运用此方法测定静脉注射DYSP-C34(16 mg/kg)后大鼠血浆中以及荷瘤小鼠组织中的药物浓度,采用DAS 2.0计算出药物半衰期t1/2z为6.98 h,药-时曲线下面积AUC(0-∞)为1025.01 h·mg/L,平均驻留时间MRT(0-∞)为9.19 h。DYSP-C34在荷瘤小鼠体内的分布结果显示,DYSP-C34可以在肿瘤组织中蓄积,并具有一定的滞留作用。综上,该文建立了大鼠血浆中DYSP-C34的HPLC-UV测定方法,并进行了方法学验证,此方法简便、快速,结果准确。阐明了DYSP-C34在静脉给药方式下大鼠体内药代动力学和荷瘤小鼠组织中的分布特征,对临床合理用药和药效学研究具有重要意义。