Orbital Period Variations Research Articles

Constraining the overcontact phase in massive binary evolution. III. Period stability of known B+B and O+B overcontact systems

Binary systems play a crucial role in massive star evolution. Systems composed of B-type and O-type stars are of particular interest due to their potential to lead to very energetic phenomena or the merging of exotic compact objects. We aim to determine the orbital period variations of a sample of B+B and O+B massive overcontact binaries, with the primary objectives of characterizing the evolutionary timescales of these systems and addressing the existing discrepancy between observational data and theoretical predictions derived from population synthesis models. We used Period04 to analyze archival photometric data going back a century for a sample of seven binary systems to measure their orbital periods. We then determine the period variations using a linear fit. We find that the period variation timescales of five truly overcontact binary systems align with the nuclear timescale, in agreement with previous findings for more massive overcontact binaries. Additionally, we noticed a clear distinction between the five systems that had been unambiguously classified as overcontact systems and both SV Cen and VFTS 066, which seem to be evolving on thermal timescales and might be misclassified as overcontact systems. In the case of the five overcontact binaries, our results indicate a noticeable mismatch between the observational data and the theoretical predictions derived from population synthesis models. Furthermore, our results suggest that additional physical mechanisms must be investigated to compare the observed variations more thoroughly with theoretical predictions.

KM UMa: An Active Short-period Detached Eclipsing Binary in a Hierarchical Quadruple System

Abstract The first detailed photometric and spectroscopic analysis of the G-type eclipsing binary KM UMa is presented, which indicates that the system is a short-period detached eclipsing binary. The radial velocity curves were calculated using the cross-correlation function method based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and our observations, which determined the mass ratio as q = 0.45 (±0.04). Based on the light curves from the Transiting Exoplanet Survey Satellite, other survey data, and our multiband observations, the positive and negative O’Connell effects have been detected evolving gradually and alternately over the last 20 yr, which can be explained by the presence of spots on the primary component. A superflare event was detected in the SuperWASP data on 2007 February 28, further indicating that KM UMa is a very active system. We calculated its energy to be 5 × 1034 erg by assuming it occurred on the primary star. Utilizing hundreds of medium-resolution spectra and one low-resolution spectrum, the equivalent width variations of the H α line were calculated, indicating the presence of a 5.21 (±0.67) yr magnetic activity cycle. The orbital period variations were analyzed using the O–C method, detecting a long-term decrease superimposed with a periodic variation. The amplitude of the cyclic variation is 0.01124 (±0.00004) day, with a period of 33.66 (±0.0012) yr, which exceeds the 5.21 yr activity cycle, suggesting that this is more likely attributable to the light travel time effect of a third body. Simultaneously, a visual companion has been detected based on the Gaia astrometric data, indicating that KM UMa is actually in a 2+1+1 hierarchical quadruple system.

Investigation of a W UMa-type contact binary GZ And in a physical triple system

GZ And is a variable star within the visually observed multiple-star system ADS 1693. Recent observations have yielded new light curves for GZ And, obtained using the Xinglong 85-cm telescope and the Transiting Exoplanet Survey Satellite (TESS) satellite. These light curves, along with radial velocity curves, were analyzed simultaneously to ascertain the fundamental physical parameters of GZ And’s components. The findings indicate that the primary star has a mass of M1 = 0.57 (4)M⊙, radius of R1 = 0.75 (2)R⊙, and luminosity of L1 = 0.42 (2)L⊙. The secondary star is characterized by a mass of M2 = 1.19 (9)M⊙, radius of R2 = 1.04 (3)R⊙, and luminosity of L2 = 0.63 (3)L⊙. Their orbital separation is determined to be a = 2.30 (6)R⊙. An analysis of the accumulated times of light minima reveals that GZ And is undergoing orbital period variations at a rate of dP/dt = −7.58 (7) × 10−8day ⋅ year−1, likely due to mass transfer from the more massive component to its lighter counterpart at a rate of dM2/dt = −9.06 (8) × 10−8M⊙⋅ year−1. Additionally, distance measurements for the component stars in ADS 1693, derived from Gaia DR3 astrometric data, suggest that ADS 1693A (GZ And) and ADS 1693B are gravitationally bound and likely originated from the same molecular cloud, sharing similar ages. This evidence supports the classification of GZ And as a W UMa-type contact binary within a physically associated triple system.

A comprehensive study of an oscillating eclipsing Algol: Y Camelopardalis

Abstract Y Camelopardalis (Y Cam) is classified as one of the oscillating eclipsing Algol (oEA) systems, which feature a $\delta$ Scuti-type pulsating component alongside mass transfer phenomena. oEA systems are invaluable for probing the evolutionary processes and internal structures of binary components, offering insights through their binary variations and oscillations. In this study, we conducted a comprehensive investigation of Y Cam utilizing high-quality photometric TESS data and high-resolution ELODIE spectra. Through our analysis, we examined the radial velocity variation, performed binary modeling, and calculated the effective temperature values of binary components. The fundamental stellar parameters, such as mass and radius, were determined with an accuracy of $\sim$2%–6%. Furthermore, we examined the orbital period variation to assess the amount of mass transfer using the available minima times of the system and three new minima times obtained from TESS light curves. Analyzing the pulsation structure of the system with the TESS data revealed the dominant pulsation period and amplitude of the pulsating component to be 0.066 d and 4.65 mmag, respectively. Notably, we observed frequency modulations with the orbital period’s frequency, along with variations in the amplitude of the highest amplitude frequency across different orbital phases. Remarkably, the amplitude reaches its peak at phases 0.5 and 1. These findings indicate a candidate for a tidally tilted pulsator. Consequently, we investigated the evolutionary status of the binary components using MESA binary evolution models, determining the age of the system to be 3.28 ± 0.09 Gyr.

Orbital Period Variation Analysis of the HS 0705+6700 Post-Common Envelope Binary

Abstract To detect additional bodies in binary systems, we performed a potent approach of orbital period variation analysis. In this work, we present 90 new mid-eclipse times of a short-period eclipsing binary system. Observations were made using two telescopes from 2014 to 2024, extending the time span of the O – C diagram to 24 years. The data obtained in the last seven years indicate significant deviations in the O – C diagram from the models obtained in previous studies. We investigated whether this variation could be explained by mechanisms such as the LTT effect or Applegate. To investigate the cyclic behaviour observed in the system with the LTT effect, we modelled the updated O – C diagram using different models including linear/quadratic terms and additional bodies. The updated O – C diagram is statistically consistent with the most plausible solutions of models that include multiple brown dwarfs close to each other. However, it has been found that the orbit of the system is unstable on short time scales. Using three different theoretical definitions, we have found that the Applegate mechanism cannot explain the variation in the orbital period except for the model containing the fifth body. Therefore, due to the complex nature of the system, further mid-eclipse time is required before any conclusions can be drawn about the existence of additional bodies.

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.

Sgr A*, M87* and OJ287 as Extreme Central Binaries of Supermassive Black Holes- -Confirmation and extension of decameter radio wave observation results through VLBI data comparison

Based on a deduced 2153±5 s orbiting period of the extreme central binary of the supermassive black hole (ECB-SMBH), at Sgr A*,that is confirmed being based on the decameter radio wave pulse observations compared with 1.3 mm wavelength very long baseline interferometry (VLBI) data from the event horizon telescope (EHT-Data), we depict moving images of Sgr A* from EHT-Data, confirming further the existence of ECB-SMBH. The results show that radio wave images of the two members of ECB-SMBH are radio-bright objects due to emissions caused by source agents accreting from a thick disk toward ECB-SMBH. We extend the confirmed concept of ECB-SMBH to the interpretation of M87*, based on two images released by Miyoshi et al. in 2022 using EHT-Data and by Lu et al. in 2023 using the 3.5 mm wavelength data from the Global Millimeter VLBI Arrays as core telescopes. For the double brilliant spots displayed in two different images of M87*, we consider them the same two objects that shift locations during the 369-day interval of the observation periods of the two images. It is concluded that M87* A and M87* B (temporarily named) are orbiting with a period of 168.8 d at velocities of (6.28±0.54)% and (16.7±1.5)% of the speed of light, respectively. For the existence of ECB-SMBH, the condition of “no gravitational wave radiation” from the SMBH is essential. Regarding the secondary BH of blazar OJ 287, we find around 58~60-year period oscillation of the orbiting period, which is recently in a shortening phase. By applying the concept of ECB-SMBH to the OJ287 primary BH, whose orbiting period is approximately 1.6 yr, we interpret that the orbital period variation of the secondary BH is not due to the radiation of gravitational waves but is caused by the orbital motions of ECB-SMBH

Orbital period change of SW Sex star TT Tri

Abstract SW Sex-type stars are the dominate population of cataclysmic variables (CVs) just above the period gap and are vital for understanding of CV evolution. We have monitored TT Tri for nearly 15 yr, and more observations yield a more reliable estimation for its orbital period variation. In this work, we present a detailed analysis about its orbital period variation. TT Tri experiences a rapid period decay with a decay rate of −5.67 × 10−11 s/s plus a period oscillation at about 9.6 years. The oscillation could be caused by the magnetic activities of the low-mass star or/and a circumbinary body, while the rapid period decrease can not be accounted for by the magnetic braking or even including an intensive disk wind. We find that mass overflow though the L3 point can take the angular momentum away effectively and that this mass overflow could account for the rapid period decay observed in TT Tri. We propose that this kind of angular momentum loss may play a crucial role in CV evolution, and further research is in progress.

BSN: Photometric Light Curve Analysis of Two Contact Binary Systems LS Del and V997 Cyg

The light curve analyses and orbital period variations for two contact binary stars, LS Del and V997 Cyg, are presented in this work which was conducted in the frame of the Binary Systems of South and North project. Ground-based photometric observations were performed at two observatories in France. We used the Transiting Exoplanet Survey Satellite (TESS) data for extracting times of minima and light curve analysis of the target systems. The O − C diagram for both systems displays a parabolic trend. LS Del and V997 Cyg’s orbital periods are increasing at rates of dP/dt = 7.20 × 10−08 days yr−1 and dP/dt = 2.54 × 10−08 days yr−1, respectively. Therefore, it can be concluded that mass is being transferred from the less massive star to the more massive component with a rate of dM/dt = –1.96 × 10−7 M ⊙ yr−1 for the LS Del system, and dM/dt =–3.83 × 10−7 M ⊙ yr−1 for V997 Cyg. The parameters of a third possible object in the system are also considered. The PHysics Of Eclipsing BinariEs Python code was used to analyze the light curves. The light curve solutions needed a cold starspot due to the asymmetry in the LS Del system’s light curve maxima. The mass ratio, fill-out factor, and star temperature all indicate that both systems are contact binary types in this investigation. Two methods were applied to estimate the absolute parameters of the systems: one method relied on the parallax of Gaia DR3, and the other used a P − M relationship. The positions of the systems are also depicted on the M − L, M − R, q − L ratio, and logMtot−logJ0 diagrams. We recommend that further observations and investigations be done on the existence of a fourth body in this system.

A targeted radio pulsar survey of redback candidates with MeerKAT

ABSTRACT Redbacks are millisecond pulsar binaries with low-mass, irradiated companions. These systems have a rich phenomenology that can be used to probe binary evolution models, pulsar wind physics, and the neutron star mass distribution. A number of high-confidence redback candidates have been identified through searches for variable optical and X-ray sources within the localization regions of unidentified but pulsar-like Fermi-LAT gamma-ray sources. However, these candidates remain unconfirmed until pulsations are detected. As part of the TRAPUM project, we searched for radio pulsations from six of these redback candidates with MeerKAT. We discovered three new radio millisecond pulsars, PSRs J0838−2827, J0955−3947, and J2333−5526, confirming their redback nature. PSR J0838−2827 remained undetected for 2 yr after our discovery despite repeated observations, likely due to evaporated material absorbing the radio emission for long periods of time. While, to our knowledge, this system has not undergone a transition to an accreting state, the disappearance, likely caused by extreme eclipses, illustrates the transient nature of spider pulsars and the heavy selection bias in uncovering their radio population. Radio timing enabled the detection of gamma-ray pulsations from all three pulsars, from which we obtained 15-yr timing solutions. All of these sources exhibit complex orbital period variations consistent with gravitational quadrupole moment variations in the companion stars. These timing solutions also constrain the binary mass ratios, allowing us to narrow down the pulsar masses. We find that PSR J2333−5526 may have a neutron star mass in excess of 2 M⊙.

A sequence of Type Ib, IIb, II-L, and II-P supernovae from binary-star progenitors with varying initial separations

Over the last decade, evidence has accumulated that massive stars do not typically evolve in isolation but instead follow a tumultuous journey with a companion star on their way to core collapse. While Roche-lobe overflow appears instrumental for the production of a large fraction of Type Ib and Ic supernovae (SNe), variations in the initial orbital period, $P_ init $, of massive interacting binaries may also produce a wide diversity of case B, BC, or C systems, with pre-SN stars endowed from minute to massive H-rich envelopes. Focusing here on the explosion of the primary donor star, originally 12.6\ we used radiation hydrodynamics and nonlocal thermodynamic equilibrium time-dependent radiative transfer to document the gas and radiation properties of such SNe, covering Types Ib, IIb, II-L, and II-P. Variations in init $ are the root cause of the wide diversity of our SN light curves, which present single-peak, double-peak, fast-declining, or plateau-like morphologies in the $V$ band. The different ejecta structures, expansion rates, and relative abundances (e.g., H, He, and can lead to a great deal of diversity in terms of spectral line shapes (absorption versus emission strength and width) and evolution. We emphasize that Halpha is a key tracer of these modulations, and that He is an enduring optical diagnostic for the presence of He. Our grid of simulations fares well against representative Type Ib, IIb, and II-P SNe, but interaction with circumstellar material, which is ignored in this work, is likely at the origin of the tension between our Type II-L SN models and observations (e.g., of SN\,2006Y). Remaining discrepancies in the rise time to bolometric maximum of our models call for a proper account of both small-scale and large-scale structures in core-collapse SN ejecta. Discrepant Type II-P SN models, with a high plateau brightness but small spectral line widths, can be fixed by adopting more compact red-supergiant star progenitors.

Search and characterization of third-body candidates around short-period binaries using Kepler and TESS data

ABSTRACT The study of the orbital period variation of short-period binary systems has been important to understand several physical phenomena, such as the emission of gravitational waves, angular momentum loss via magnetic braking, matter transfer between the components, apsidal motion, quadrupole moment variation, and presence of circumbinary bodies. With the advent of large space missions, e.g. Kepler and Transiting Exoplanet Survey Satellite (TESS), an enormous amount of high-precision photometric data with temporal coverage from years to decades has become available. Thus, in this work, we propose to study the orbital period variation of a sample of 253 binary that was observed by both Kepler and TESS and therefore with a temporal coverage of more than 10 yr. The main goal of this paper is the search and characterization of third bodies. Based on the periodicity analysis of the observed minus calculated (O − C) diagram of the sample, 75 of them showed periodic variation and therefore were classified as binary systems with third-body candidates, while the remaining 178 did not show periodic variations. This result is a two-fold increase in tertiary candidates around binary systems compared to the study carried out with only Kepler data. Although our estimated rate of third-body candidates (∼30 per cent) is higher than that obtained only with Kepler data (∼20 per cent), it should be taken as a lower limit.

Update on WASP-19

Tidal interaction between a star and a close-in massive exoplanet causes the planetary orbit to shrink and eventually leads to tidal disruption. Understanding orbital decay in exoplanetary systems is crucial for advancing our knowledge of planetary formation and evolution. Moreover, it sheds light on the broader question of the long-term stability of planetary orbits and the intricate interplay of gravitational forces within stellar systems. Analyzing Transiting Exoplanet Survey Satellite (TESS) data for the ultra-short period gas giant WASP-19, we aim to measure orbital period variations and constrain the stellar tidal quality parameter. For this, we fitted the TESS observations together with two WASP-19 transits observed using the Las Cumbres Observatory Global Telescope (LCOGT) and searched for orbital decay in combination with previously published transit times. As a result, we find a deviation from the constant orbital period at the 7σ level. The orbital period changes at a rate of P˙=−3.7±0.5msyear−1, which translates into a tidal quality factor of Q★′=(7±1)×105. We additionally modeled WASP-19 b’s phase curve using the new TESS photometry and obtained updated values for the planet’s eclipse depth, dayside temperature, and geometric albedo. We estimate an eclipse depth of 520±60 ppm, which is slightly higher than previous estimates and corresponds to a dayside brightness temperature of 2400±60 K and geometric albedo of 0.20±0.04.

Improved Period Variations of 32 Contact Binaries with Rapidly Decreasing Periods in the Galactic Bulge

We present detailed analyses of updated eclipse timing diagrams for 32 contact binary merger candidates in the Galactic bulge. The photometric data was obtained from 2016 to 2021 using the Korea Microlensing Telescope Network with the 1.6 m telescopes located at three southern sites (CTIO, SAAO, and SSO). The times of minimum lights were determined by applying the binary-star model to full light curves created at half-year intervals from the observations. The orbital period variations of the binary systems were analyzed using the O − C diagrams from our new timings with the others published in the literature, which are based on the OGLE observations from 2001 to 2015. As results, the orbital periods and period-decreasing rates of 32 binary systems were located to be in the ranges of 0.370 to 1.238 days and from −3.0 to −13.1 × 10−6 day yr−1, respectively. Out of these stars, 24 systems show a combination effect of a parabola and a light travel time caused by a third body, and their outer orbital periods are in the range of 9.1–26.5 yr. We propose that all of our merger candidates need additional monitoring observations to study a luminous-red nova progenitor.

Correction to: Investigation on the orbital period variations of NN Ser: implications for the hypothetical planets, the Applegate mechanism, and the orbital stability

Correction to: Investigation on the orbital period variations of NN Ser: implications for the hypothetical planets, the Applegate mechanism, and the orbital stability

Investigation on transit observations of the WASP-10 and WASP-11 systems

In the study, we present the results of new transit observations of two hot Jupiter WASP-10 b and WASP-11 b using the T100 telescope in Turkey. By analyzing the new transit light curves with the MCMC method through EXOFASTv2, we updated the physical parameters of two hot-Jupiter systems. The updated parameters are in agreement with the previously determined values within the uncertainties except eccentricity and impact factor. Starspot activity, noticed in previous studies, was not clearly detectable due to our highly scattering transit light curves of both systems. We determined an updated linear ephemeris and orbital period for the two systems by combining our new mid-transit times with the ones in the literature. There is no significant evidence for the orbital period variation of the systems in the most-updated O−C diagram. In addition, we could not find any strong signals for both two systems in the period analysis.

Investigation on the orbital period variations of NN Ser: implications for the hypothetical planets, the Applegate mechanism, and the orbital stability

ABSTRACT We present 36 new mid-eclipse times obtained between 2017 and 2023 using the T100 telescope in Turkey, extending the time span of the O − C diagram to 25 yr. Once again, these new observations show significant deviations from previous published models that were able to explain the observed variations of the binary period. We investigate two plausible explanations for this variability: the light travel time (LTT) effect due to the presence of one or two invisible low-mass (planetary) companion(s) in distant circumbinary orbits; other mechanisms, like e.g. the Applegate mechanism, associated with the magnetic cycles of the M-dwarf component of the WD + dM binary. Through Markov Chain Monte Carlo analyses, we demonstrate that the observed O − C variability can be explained by the presence of a planet with a minimum mass of ∼9.5MJ. This circumbinary planet orbits around the binary system with a period of about 19.5 yr, maintaining a stable orbit for a timeline of 10 Myr. By adding a weak LTT signal from a secondary hypothetical planet we achieve statistically better results. However, the orbits of the bodies in a two-planet system remain stable only for a small range of the parameter space. The energy required to power the Applegate and other Applegate-like mechanisms is too high to explain the period variations observed. Thus, on the one hand there is substantial evidence supporting the existence of a planet in the NN Ser system, but on the other hand there are also compelling indications that cast doubt on the existence of a second hypothetical planet.

Period Change Analysis of a W UMa-type Binary: V417 Aquilae

Light curve analysis investigated the orbital period variations of the short period, overcontact eclipsing binary system, and V417 Aquilae (V417 Aql). The system was observed using a 0.70-meter telescope with a CCD photometric system using B and V filters at the Regional Observatory for the Public, Songkhla, Thailand, on 2 July 2021 UT. The light curve constructed by the photometric method for each filter was analyzed to find the period change of the system. It is found that the V417 Aql system is undergoing a long-term decrease of rate 0.00251 seconds/year. The reduction in the period showed that the distance between the stars was decreased according to Angular Momentum Loss (AML) theory. V417 Aql residuals tend to be periodic, indicating there might be a third body in the system. The calculation shows that the third body’s distance, period, and mass function are about 1.97 AU, 47.7 years, and 0.19Mʘ, respectively.

Orbital Period Variations in HT Cas: Evidence for Additional Angular Momentum Loss and a High-eccentricity Giant Planet

We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, combined with historical timings, spanning ∼42 yr, we detect a secular decrease in the orbital period at a rate of and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of M 3 ≃ 14M Jup that is moving on a highly eccentric orbit (e = 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.

Light Curve Analysis of the AP Dor Binary System using Ground-based and TESS Observations

The short-period eclipsing binary AP Dor’s first in-depth and multiband photometric solutions are presented. We made use of our eight nights of ground-based opportunity at a southern hemisphere observatory, and twelve sectors of TESS observations. We extracted eight and 1322 minima from our observations and TESS, respectively. We suggest a new linear ephemeris based on the trend of orbital period variations using the Markov chain Monte Carlo (MCMC) approach. The PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the MCMC approach were utilized for the light curve analysis. This system did not require a starspot for the light curve solutions. We calculated the absolute parameters of the system by applying the Gaia DR3 parallax method. The orbital angular momentum (J 0) of AP Dor indicates that this system is located in a region corresponding to contact binaries. According to our results, this system is an overcontact binary system with a mass ratio of 0.584, a fillout factor of 48%, and an inclination of 53°. The positions of component stars in the AP Dor system on the Hertzsprung–Russell diagram are found.