Orbital Period Changes Research Articles

Period Analysis, Roche Modeling and Absolute Parameters for AU Ser, an Overcontact Binary System

CCD photometric data collected at UnderOak Observatory (UO) and Desert Bloom Observatory (DBO) in three bandpasses (B, V and I_C) produced 10 new times of minimum for AU Ser which were used to revise the linear ephemeris. These results captured in 2011 and 2018 reinforced a longstanding observation that the shape of the light curve from this W UMa binary system (P=0.386497 d) is highly variable. Significantly skewed peaks and differences at maximum light were detected during quadrature which could only be simulated during Roche modeling by positioning a hot spot on the secondary star close to the neck between both constituents. Historically this system has been variously classified as an F8, G5 and K0 system; however, this study supports more recent reports that AU Ser is best described as spectral type K1V-K2V. A fresh assessment of eclipse time residuals over the past 80 years has provided additional insight regarding cyclical changes in orbital period experienced by this interesting variable star.

Hubble Space Telescope Far-UV Spectroscopy of the Short Orbital Period Recurrent Nova CI Aql: Implications for White Dwarf Mass Evolution

Abstract An Hubble Space Telescope Cosmic Object Spectrograph Far UV spectrum (1170 Å to 1800 Å) was obtained for the short orbital period recurrent novae (T Pyxidis subclass), CI Aquilae. CI Aql is the only classical Cataclysmic variable (CV) known to have two eclipses of a sensible depth per orbit cycle and also to have pre- and post-outburst light curves that are steady enough to allow estimates of mass and orbital period changes. Our far-ultraviolet (FUV) spectral analysis with model accretion disks and non-LTE high-gravity photospheres, together with the Gaia parallax, reveal that CI Aql's FUV light is dominated by an optically thick accretion disk with an accretion rate of the order of 4 × 10−8 M ☉ yr−1. Its database of light curves, radial velocity curves, and eclipse timings is among the best for any CV. Its orbit period (P), dP/dt, and reference time are rederived via a simultaneous analysis of the three data types, giving a dimensionless post-outburst dP/dt of (−2.49 ± 0.95) × 10−10. The lack of information on the loss of orbital to rotational angular momentum leads to some uncertainty in the translation of dP/dt to the white dwarf (WD) mass change rate, dM1/dt, but within the modest range of to +7.8 × 10−8 . The estimated WD mass change through outburst for CI Aql, based on simple differencing of its pre- and post-outburst orbit period, is unchanged from the previously published . At the WD's estimated mass increase rate, it will terminate as a Type Ia supernova within 10 million years.

A Detached Eclipsing Binary with a Period Shorter than 0.2 Days in a Triple System

W UMa-type binary stars have an apparent short-period cutoff around 0.2 days. Close binaries with orbital periods shorter than this limit are very useful for understanding the formation and evolution of this type of binaries. 2MASS J11553339+3544399 (hereafter J1155) is a red-dwarf binary with a period of 0.199724 days. Multicolor (V, R, Rc, I, Ic, W) light curves (LCs) for the ultrashort-period eclipsing binary (EB) J1155 are presented and analyzed by using the Wilson-Devinney (W-D) code. We find that J1155 belongs to a rare group of detached red-dwarf EB with periods below the period limit of contact binaries (the other two are BW03 V38 and GSC 2314-0530). It has a high-mass ratio of 0.90. The primary component (the more massive and hotter star) is filling 90% of the critical Roche lobe, while the secondary one is filling about 84.8%. The masses and radii of the two components are estimated as M1 = 0.475 ± 0.035 M⊙, M2 = 0.441 ± 0.044 M⊙, R1 = 0.516 ± 0.089 R⊙, and R2 = 0.491 ± 0.105 R⊙, respectively. By analyzing all available times of light minimum, the orbital period changes of the binary system are investigated for the first time. We find that the (O − C) (observed-calculated) diagram shows a cyclic oscillation with an amplitude of 0.00326 days and a period about 9.84 years. This oscillation is explained as the light-travel time effect (LTTE) via the presence of a third body. The mass of the third component in the triple system is computed to be M3 sin (i′) ∼ 0.127 M⊙. The orbital distance between the central binary and the tertiary component is about 4.0 au. It is possible that the third body and the magnetic braking may play important roles in the formation and evolution of J1155 by drawing angular momentum from the central system.

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

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

First photometric study of a short-period detached eclipsing binary NSVS 10441882

NSVS 10441882 is a newly discovered eclipsing binary system with strong magnetic activity and an orbital period of ∼ 0.5166 days. In order to study this eclipsing binary system, we analyzed its first four-color (BVRcIc) light curves. The observed light curves were asymmetric, so we used the 2013 version of the Wilson–Devinney (W–D) program with cool star-spots to analyze these data. We discovered that NSVS 10441882 is a detached total eclipsing binary system with an orbit inclination of 85°.34 ± 0.07 and a mass ratio of q = 0.94 ± 0.03. Based on the CCD times of the light minima according to our observations and those reported previously, the orbital period changes of NSVS 10441882 were studied using the traditional O–C method for the first time. The O–C diagram of the target exhibited a cyclic oscillation with a period of 16.7 ± 0.20 years and an amplitude of 0.00349 ± 0.00029 days, probably due to the presence of an unseen third body. If we assume that the total mass of NSVS 10441882 is 1.3M⊙ (according to our calculated results for the average color index and mass ratio), then the mass of the third body is no less than 0.12 ± 0.01 M⊙. Moreover, the orbital evolution of the central system will be accelerated due to the presence of this additional component.

Analysis of Structure and Evolution of Binary System GV Leo

GV Leo is a W Ursa eclipsing binary with an orbital period of 0.266727 day. From the previous investigation of its light curve, it was found that this binary system has a continuous orbital period change. A light curve of GV Leo was analyzed using program MaxIm DL3 and its period change was also calculated. The results revealed that the orbital period of GV Leo was continuously decreased at rate of 0.004524349151 seconds per year to 0.005440856529 seconds per year and using PHOEBE software was used to compute the best system is parameters. The over contact binary system with g = 0.829, i = 69.86 degree. The temperature of primary star and secondary star were 5,020 K and 5,650 K respectively. From the analysis of physical parameters and model, it was found that GV Leo had a contact characteristic with high mass ratio. It is possible that the evolution of GV Leo would be a single star due to mass transfer of the system.

Orbital period changes of the W UMa binary YY Eri

Orbital period changes of the W UMa-type binary YY Eri are analyzed by using all photoelectric and ccd times of light minimum. The results show that its orbital period is undergoing a secular increase superposed on two cyclic oscillations. The continuous increase at the rate of may be accounted for by mass transfer from the less massive companion to the more massive one. Two periodic variations with periods of 38.6192 and 22.3573 yr may be attributed to the light-time effect of a faint third star and the cyclic magnetic activity of the system, respectively.

Non-conservative mass transfer in stellar evolution and the case of V404 Cyg/GS 2023+338

We consider donor evolution and mass transfer in the microquasar V404 Cyg/GS 2023+338. Based on X-ray observations of its two outbursts, its average mass accretion rate is substantially lower than our model mass-loss rate from its low-mass giant donor. A likely solution to this discrepancy is that a large fraction of the mass flowing from the donor leaves the binary in the form of outflows from the accretion disc around the accretor. The outflow can be parameterizes by the fractions of the mass and angular momentum leaving the system. We calculate the latter as a function of the radius of the accretion disc from which the outflow takes place. We then perform detailed evolutionary calculations for V404 Cyg. Given our estimated average accretion rate, $>$70 per cent of the mass lost from the donor has to leave the binary. The allowed solutions for the actual donor mass loss rate are parameterized by our two outflow parameters. Our results are in agreement with the observed outflows from the outer disc as well as with the variable near-Eddington accretion observed during the outbursts, compatible with outflows from the vicinity of the black hole. We then calculate the expected rate of the orbital period change. Its future measurements can constrain the presence of an outflow in V404 Cyg and its parameters.

Orbital Period Changes in WZ Sagittae

We report a long-term (1961–2017) study of the eclipse times in the dwarf nova WZ Sagittae, in an effort to learn its rate of orbital-period change. Some wiggles with a timescale of 20–50 years are apparent, and a connection with the ∼23 year interval between dwarf-nova eruptions is possible. These back-and-forth wiggles dominate the O–C diagram, and prevent a secure measurement of the steady rate of orbital-period change.

New CCD photometric investigation of the early-type overcontact binary BH Cen in the young star-forming Galactic cluster IC 2944

BH Cen is a short-period early-type binary with a period of 0.792d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A3 = 0.024 d and a period of P3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass transfer. The continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of Ṁ2 = 2.8 × 10−6M⊙ per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M⊙ at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.

On orbital period changes of two low-mass-ratio and deep-contact binaries: FN Cam and KN Per

The orbital period changes of two low-mass-ratio and deep-contact binaries, FN Cam and KN Per, are investigated by using all available times of light minimum taken from the databases and literature. It is found that the orbital periods of FN Cam and KN Per show secular increase at a rate of P˙=4.38×10−7 days year−1 and P˙=4.18×10−7 days year−1, respectively. The secular period increase suggests that FN Cam and KN Per are undergoing continuous mass transfer from the less massive secondary component to the more massive primary one. A statistical analysis of 53 low-mass-ratio and deep-contact binaries indicates that all of them should contain at least a continuous period change (secular increase/decrease or cyclic oscillation). Moreover, the rates of the secular period variations can be at a common level of P˙∼10−7 days year−1. In addition, the cyclic period oscillation has been detected for only 43% of sample stars, which indicates that it should be not popular for all low-mass-ratio and deep-contact binaries.

Evolution of Angular Momentum and Orbital Period Changes in Close Double White Dwarf Binaries

We have presented the evolution of angular momentum and orbital period changes between the component spins and the orbit in close double white dwarf binaries undergoing mass transfer through direct impact accretion over a broad range of orbital parameter space. This work improves upon similar earlier studies in a number of ways: First, we calculate self-consistently the angular momentum of the orbit at all times. This includes gravitational, tides and mass transfer effects in the orbital evolution of the component structure models, and allow the Roche lobe radius of the donor star and the rotational angular velocities of both components to vary, and account for the exchange of angular momentum between the spins of the white dwarfs and the orbit. Second, we investigate the mass transfer by modeling the ballistic motion of a point mass ejected from the center of the donor star through the inner Lagrangian point. Finally, we ensure that the angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum and orbital period changes of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum and orbital period of the orbit at the expense of the spin angular momentum of the donor and accretor. We find that our analysis yields an increase in the predicted number of stable systems compared to that in the previous studies, survive the onset of mass transfer, even if this mass transfer is initially unstable. In addition, as a consequence of the tidal coupling, systems that come into contact near the mass transfer instability boundary undergo a phase of mass transfer with their orbital period.

Further Evidence of a Brown Dwarf Orbiting the Post-Common Envelope Eclipsing Binary V470 Cam (HS 0705+6700)

Abstract Several post-common envelope binaries have slightly increasing, decreasing or oscillating orbital periods. One of several possible explanations is light travel-time changes, caused by the binary centre-of-mass being perturbed by the gravitational pull of a third body. Further studies are necessary because it is not clear how a third body could have survived subdwarf progenitor mass-loss at the tip of the Red Giant Branch, or formed subsequently. Thirty-nine primary eclipse times for V470 Cam were secured with the Philip Wetton Telescope during the period 2016 November 25th to 2017 January 27th. Available eclipse timings suggest a brown dwarf tertiary having a mass of at least 0.0236(40) M⊙, an elliptical orbit with an eccentricity of 0.376(98) and an orbital period of 11.77(67) years about the binary centreof- mass. The mass and orbit suggest a hybrid formation, in which some ejected material from the subdwarf progenitor was accreted on to a precursor tertiary component, although additional observations would be needed to confirm this interpretation and investigate other possible origins for the binary orbital period change.

Reanalysis of the orbital period variations of two DLMR overcontact binaries: FG Hya and GR Vir

We investigate orbital period changes of two deep, low mass ratio (DLMR) overcontact W UMa-type binaries, FG Hya and GR Vir. It is found that the orbital period of FG Hya shows a cyclic change with a period of . The cyclic oscillation may be due to a third body in an eccentric orbit, while the orbital period of GR Vir shows a periodic variation with a period of and an amplitude of A = 0.0352 d. The periodic variation of GR Vir can be interpreted as a result of either the light-time effect of an unseen third body or the magnetic activity cycle.

TYC 1337-1137-1 and TYC 3836-0854-1: Two Low-mass Ratio, Deep Overcontact Systems Near the End Evolutionary Stage of Contact Binaries

New high-precision CCD photometric light curves of two contact binary stars, TYC 1337-1137-1 and TYC 3836-0854-1, are displayed and analyzed by using the Wilson–Devinney (W–D) program. The light curve solutions show that both of them are low-mass ratio, deep overcontact binary systems with a mass ratio of q = 0.1716 ± 0.0010 and a high fillout factor of f = 76.0 ± 2.9% for TYC 1337-1137-1, and q = 0.1900 ± 0.0032 and f = 79.4 ± 7.9% for TYC 3836-0854-1, respectively. These results indicate that they are near the end evolutionary stage of contact binaries. The absolute parameters were calculated by using the new method of mass–radius relationship (0.238 ± 0.009 M⊙ and 1.386 ± 0.050 M⊙ for TYC 1337-1137-1, 0.228 ± 0.014 M⊙ and 1.20 ± 0.07 M⊙ for TYC 3836-0854-1, respectively). The preliminary orbital period analysis suggests that long-term period increases exist for both of them, which may be interpreted in two possible ways. A first possibility is mass transfer conservation from the less massive component to the more massive one leading to an orbital period increase. In this case, when their orbital angular momentum is less than three times the total spin angular momentum, they may evolve into a rapidly rotating single star. A second possibility is that the parabolic variation in the (O − C) diagram is only a part of a long-period cyclic change caused by a potential third body. In future, more high-precision observations of these two binaries are needed to confirm the form of orbital period changes.

Is There a Substellar Object Orbiting the Solar-like Stable Contact Binary V2284 Cyg?

V2284 Cyg is a neglected W UMa-type binary star for photometric investigations. Monitored by the Kepler Space Telescope from 2009 to 2013, its light curves are continuously stable, suggesting that both components are inactive during this time interval. Based on the short-cadence observations, we determined the photometric solutions by using the 2013 version of the Wilson-Devinney code. These parameters reveal that V2284 Cyg is a W-type system with a degree of contact factor of f = 39.23% and a mass ratio of q = 2.90. Meanwhile, hundreds of times of minimum light were obtained and applied to analyze the orbital period changes. In the O-C diagram, a small-amplitude cyclic oscillation (A3 = 0.00030 days and T3 = 2.06 years) superimposed on a secular decreasing was found. The continuous decreasing may be a result from the mass transfer from the more massive component to the less massive one. With the long-term decreasing of the orbital period, this binary will evolve into a deeper contact system. Because the light curve is stable, the cyclic variation is plausibly explained as the light-travel time effect (LTTE) due to the presence of an additional body. The mass of the companion is . If the orbital plane inclination is a random distribution, it is a brown dwarf with 66.7% probability. Therefore, the companion of V2284 Cyg is possibly the first candidate of the brown dwarf orbiting around contact binary, where both component are sharing a common convective envelope.

Photometric study and period analysis of the W UM-type binary system QW Gem

New multi-color photometric observations of the previously unstudied contact binary QW Gem are presented. Completely covered BV RI band light curves were obtained, including four new times of light minima. The light curves were simultaneously analyzed with the 2013 version of the Wilson-Devinney method, assuming a third light. The photometric solutions confirm that QW Gem is a W-type W UMa system with a fill-out factor of . The absolute parameters of the components were determined to be , , , , and . The orbital period change of QW Gem was investigated by the method using all available data. The results show that this binary system could have undergone a continuous orbital period decrease during the past two decades at a rate of about . In addition, a small-amplitude oscillation was detected to be superimposed on a long-term decrease.

Photometric study and orbital period analysis of the W UMa type contact binary VZ Psc

VZ Psc is a W-type contact binary system with a short period of 0.26125897 days. B, V, Rc and Ic light curves of the eclipsing binary system were obtained by using the 1.0 m reflecting telescope at Weihai Observatory of Shandong University. By collecting 136 times of minimum light, we studied the orbital period change of VZ Psc. A sinusoidal variation was discovered in the O−C diagram, and the amplitude of 0.d0023 and the period of 17.7 year were obtained. This can be caused by Applegate mechanism or light-time effect. Both the mechanisms are suited according to our investigation, but we prefer the latter that the light-time effect due to the presence of a third body results in the cyclic variation. By using the W-D program, we analyzed the four color light curves. Because of the asymmetric light curves and the possible third body, we used the spot mode of W-D program with and without L3. We found that a hot spot on the primary component with the third light leads to the best result. A very high filling factor of 94.4% ± 2.8% and orbit inclination of 53.2° were obtained.

The first photometric investigation and orbital period variation analysis of the W UMa type binary IK Bootis

Abstract With new CCD observations of the W UMa type binary IK Boo, we present the first investigation of photometric parameters and orbital period change. The BVRc light curve fit shows that IK Boo is a W-type contact system with a mass ratio of q = 1.146 and a shallow contact with a fill-out factor of f = 2.22%. The orbital period decrease was found to be a rate of −3.28 × 10−7 d yr−1, corresponding to a mass transfer from the more massive to the less massive component with a rate of −2.83 × 10−6 M⊙ yr−1. The inner and outer critical Roche lobes will contract and cause the contact degree to increase. Therefore, IK Boo may evolve into a deeper contact system. Furthermore, a possible cyclic variation was found with a period of 9.74 yr, which could be explained by the light-travel time effect due to the existence of a third companion in the system.

Cyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMa

Abstract DV UMa is an eclipsing dwarf nova with an orbital period of ∼2.06 hr, which lies just at the bottom edge of the period gap. To detect its orbital period changes, we present 12 new mid-eclipse times by using our CCD photometric data and archival data. The latest version of the O–C diagram, combined with the published mid-eclipse times in quiescence, and spanning ∼30 years, was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of years and an amplitude of s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object, because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as . If the third body is in the orbital plane (i.e., ) of the eclipsing pair, this would indicate it is a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of ∼8.6 au in an eccentric orbit (e = 0.44).