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Deep, Low Mass Ratio Overcontact Binary Systems. IX. V345 Geminorum with a Bright Visual Pair
CCD photometric observations of the visual binary, V345 Geminorum,obtained from 2007 January 24 to 2009 March 22, are presented. Whencomparing the light curves in 2007 and 2008, it is found that thereappears to be an O'Connell effect in the light curves of 2008. Fromthose observations, two sets of photometric solutions were deduced usingthe 2003 version of the W-D program. The results indicated that V345 Gemis a low mass ratio overcontact binary with f = 72.9%(±3.1%). Theasymmetric light curves in 2008 may be attributed to the activity ofstarspot, whose area is up to 1.55% of the area of the more massivecomponent. The contributions of the third light to the total light areapproximately 20% in the BVR bands. The absolute physical parameters forV345 Gem were obtained first. From the log L-log M diagram of thebinary-star evolution, the primary component is an evolved star. Fromthe O-C curve for V345 Gem, it is discovered that there exists along-term period increase with a cyclic variation. The period andamplitude of the cyclic variation are P 3 =646.7(±0.7) day and A = 0fd0019(±0fd0002), which may becaused by the light-time effect via the assumed third body. If it istrue, the visual binary V345 Gem may be a quadruple star. The kind ofadditional component may remove angular momentum from the centralsystem, which may play an important role for the formation and evolutionof the binary. The secular period increases at a rate of dP/dt = +5.88× 10-8 d yr-1, indicating that the masstransfers from the less massive component to the more massive component.With mass transferring, the orbital angular momentum decreases while thespin angular momentum increases. When J spin/J orb> 1/3, this kind of deep, low mass ratio overcontact binary withsecular period increase may evolve into a rapid-rotating single star.
| BVR Observations and Period Variation of the Neglected Contact Binary V343 Orionis
BVR light curves of V343 Orionis were observed with the 85 cm telescopeat Xinglong Station of the National Astronomical Observatories of theChinese Academy of Sciences, in 2007 and 2008. Using the Wilson-Devinneyprogram, the photometric solution of V343 Ori was first deduced fromthose observations. Photometric results indicated that V343 Ori is anA-subtype W Ursae Majoris binary, whose mass ratio and overcontactdegree are q=0.253(±0.004) and f=86.9%(±2.1%),respectively. The asymmetric light curves (i.e., O'Connell effect) weremodeled by the spot model. The spot area is up to 1.21% of the area ofthe more massive component. All light minimum times for V343 Ori,spanning over 80 yr, were used in analyzing the orbital period change.From the O-C curve, there exists a long-term orbital period increase ata rate of dP/dt=+4.32×10 d yr, which may be caused by the masstransfer from the less massive component to the more massive one. Withmass transfer, the orbital angular momentum decreases while the spinangular momentum increases. When J >13J, this kind of binary (e.g.,V343 Ori), with high overcontact degree and period increase, may evolveinto a rapid-rotating single star.
| Energy transfer and its effects on the secondaries in W Ursae Majoris type contact binaries
Based on the physical parameters of 133 W Ursae Majoris (W UMa) typecontact binaries, energy transfer and its effects on the secondaries inW UMa contact binaries are investigated. Relations are given between themass ratio (q) for W UMa contact binaries and the relative energytransfer rates, i.e. U1, the ratio of the transferredluminosity to the surface luminosity of the primary, and U2,the ratio of the transferred luminosity to the nuclear luminosity of thesecondary. The theoretical curves(U1 versus q andU2 versus q) are derived based on various assumptions: thatthe two components in each W UMa system are nearly identical ineffective temperature and just fill their inner Roche lobes, and theprimaries are zero-age main-sequence stars. Although these curves canreflect the distribution of U1 and U2 versus q,some observational systems deviate significantly from these curves. Thisresults mainly from the difference in effective temperatures of thecomponents of W UMa systems. The radius and the density of the secondaryare related to the relative energy transfer rate U2: thehigher U2, the greater the expansion and the lower thedensity of the secondary in a W UMa system. In addition, it is foundthat the temperature difference of W UMa binary components is correlatedwith the relative energy transfer rate U1 and decreases withincreasing U1. This might suggest that there is a thermalcoupling between the two components in W UMa contact binaries, and thatthe classification of W UMa contact binaries into A or W types dependson the energy transfer from the primary to the secondary. Thetemperature difference of W UMa binary components is poorly correlatedwith the mass of the primary. This suggests that the properties of thecommon envelope of a W UMa contact binary might not have a significanteffect on the energy transfer between the two components.
| B.R.N.O. Contributions #36, Times of minima
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| BAV-Results of observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| B.R.N.O. Times of minima
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| Angular momentum and mass evolution of contact binaries
Various scenarios of contact binary evolution have been proposed in thepast, giving hints of (sometimes contradictory) evolutionary sequencesconnecting A- and W-type systems. As the components of close detachedbinaries approach each other and contact binaries are formed, followingevolutionary paths transforms them into systems of two categories:A-type and W-type. The systems evolve in a similar way but underslightly different circumstances. The mass/energy transfer rate isdifferent, leading to quite different evolutionary results. Analternative scenario of evolution in contact is presented and discussed,based on the observational data of over one hundred low-temperaturecontact binaries. It results from the observed correlations amongcontact binary physical and orbital parameters. Theoretical tracks arecomputed assuming angular momentum loss from a system via stellar wind,accompanied by mass transfer from an advanced evolutionary secondary tothe main-sequence primary. A good agreement is seen between the tracksand the observed graphs. Independently of details of the evolution incontact and a relation between A- and W-type systems, the ultimate fateof contact binaries involves the coalescence of both components into asingle fast rotating star.
| High Fill-Out, Extreme Mass Ratio Overcontact Binary Systems. VIII. EM Piscium
CCD photometric observations of the newly discovered close binary, EMPiscium, obtained from 2006 December 4 to 2008 January 7, are presented.The light curves are symmetric and show complete eclipses with aneclipse duration of 54 minutes. When comparing the present light curveswith those published by González-Rojas et al., it is found thatthe depths of the two minima of the light curve have been interchanged,and the positive O'Connell effect has disappeared. The symmetric lightcurves in R and I bands were analyzed with the 2003 version of the W-Dcode. It is found that EM Piscium is a high fill-out overcontact binarysystem (f = 95.3 ± 2.7%) with an extreme mass ratio of q =0.1487, suggesting that it is on the late evolutionary stage oflate-type tidal-locked binaries. Based on the nine instances of lightminimum that we determined and those published by previousinvestigators, it is discovered that the orbital period shows a cyclicperiod variation with a period of 3.3 years, while it undergoes acontinuously rapid increase at a rate of dP/dt = +3.97 ×10-6 days year-1. The cyclic periodreveals the presence of a tertiary companion, which may play animportant role for the formation and evolution of the overcontact binaryby drawing angular momentum from the central system via Kozaioscillation or a combination of Kozai cycle and tidal friction. The highfill-out, the extreme mass ratio, and the rapid period increase maysuggest that the binary system is quickly evolving into a rapid-rotatingsingle star.
| The evolutionary status of W Ursae Majoris-type systems
Well-determined physical parameters of 130 W Ursae Majoris (W UMa)systems were collected from the literature. Based on these data, theevolutionary status and dynamical evolution of W UMa systems areinvestigated. It is found that there is no evolutionary differencebetween W- and A-type systems in the M-J diagram, which is consistentwith the results derived from the analysis of observed spectral type andof M-R and M-L diagrams of W UMa systems. M-R and M-L diagrams of W- andA-type systems indicate that a large amount of energy should betransferred from the more massive to the less massive component, so thatthey are not in thermal equilibrium and undergo thermal relaxationoscillation. Moreover, the distribution of angular momentum, togetherwith the distribution of the mass ratio, suggests that the mass ratio ofthe observed W UMa systems decreases with decreasing total mass. Thiscould be the result of the dynamical evolution of W UMa systems, whichsuffer angular momentum loss and mass loss as a result of the magneticstellar wind. Consequently, the tidal instability forces these systemstowards lower q values and finally to rapidly rotating single stars.
| Contact Binaries with Additional Components. III. A Search Using Adaptive Optics
We present results of the Canada-France-Hawaii Telescope adaptive optics(AO) search for companions of a homogeneous group of contact binarystars, as a contribution to our attempts to prove the hypothesis thatthese binaries require a third star to become as close as observed. Inaddition to directly discovering companions at separations of>=1″, we introduced a new method of AO image analysis utilizingdistortions of the AO diffraction ring pattern at separations of0.07″-1″. Very close companions, with separations in thelatter range, were discovered in the systems HV Aqr, OO Aql, CK Boo, XYLeo, BE Scl, and RZ Tau. More distant companions were detected in V402Aur, AO Cam, and V2082 Cyg. Our results provide a contribution to themounting evidence that the presence of close companions is a very commonphenomenon for very close binaries with orbital periods <1 day.Based on observations obtained at the Canada-France-Hawaii Telescope,which is operated by the National Research Council of Canada, theInstitut National des Sciences de l'Univers of the Centre National de laRecherche Scientifique of France, and the University of Hawaii.
| B.R.N.O. Contributions #34
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Deep, Low Mass Ratio Overcontact Binary Systems. VII. QX Andromedae in the Intermediate-Age Open Cluster NGC 752
QX Andromedae is a short-period eclipsing binary in the intermediate-ageopen cluster NGC 752. Charge-coupled device photometric observations ofthe close binary system obtained from 2004 November 13 to 2006 November18 are presented. It is confirmed that the light curves show partialeclipses, and night-to-night intrinsic variations are seen. As in thecase of AH Cancri in the old open cluster M67, the light curve of QX Andseems to change between A and W types. Both the short- and long-termlight variations suggest that QX And shows strong magnetic activity,which is in agreement with its X-ray observations. The symmetric lightcurves in B and V bands obtained the night of 2004 November 13 wereanalyzed with the new version of the W-D code. It is found that QX Andis a deep overcontact binary system with a high degree of overcontact off = 55.9% and a low mass ratio of q = 0.2327, suggesting that it is inthe late stage of overcontact evolution. Based on our 23 times of lightminimum, including four recently published eclipse times, the orbitalperiod of the eclipsing binary was revised. It was discovered that theorbital period shows a continuous period increase at a rate of dP/dt =+2.48 × 10-7 days yr-1, which can beinterpreted as a mass transfer from the less massive component to themore massive one. As the period increases, the mass ratio of the systemwill decrease. It may finally evolve into a rapid-rotating single starwhen it meets the more familiar criterion that the orbital angularmomentum is less than 3 times the total spin angular momentum. Theexistence of QX And in the late evolutionary stage of an overcontactbinary in the intermediate-age open cluster NGC 752 indicates that itmay undergo strong cluster stellar interaction. This means it had a veryshort initial orbital period and could have evolved into the presentevolutionary state within the cluster age. By comparing with theevolutionary state of TX Cnc in M44, it is estimated that the lifetimeof overcontact binaries may be no less than 1 Gyr.
| Formation and Evolution of W Ursae Majoris Contact Binaries
The origin and evolution of W UMa systems are discussed based on All SkyAutomated Survey (ASAS) data and the mean kinematic ages of foursubgroups of 97 field contact binaries (FCBs). The period distributionof eclipsing binaries discovered by ASAS suggests that a period limit totidal locking for the close binaries is about 2.24 days, so that most WUMa systems might be formed from detached binaries with periodsP<~2.24 days, and a maximum advanced time from a detached system to aW UMa is about 3.23 Gyr. Moreover, the secular evolution of the angularmomentum (AM), the system mass, and the orbital period of 97 FCBs wereinvestigated according to the mean kinematic ages, which were setaccording to AM bins. AMs, systemic masses, and orbital periods wereshown to be decreasing with kinematic age. Their first-order decreasingrates have been determined as J˙/J=1.86×10-10yr-1, M˙/M=0.95×10-10 yr-1,and P˙/P=1.24×10-10 yr-1, and theaverage amplification (A¯=dlnJ/dlnM) is derived to be 1.96. Theseare lower than those derived from detached chromospherically activebinaries (CABs). This suggests that the magnetic activity level of FCBsis indeed weaker than that of CABs. Meanwhile, the decreasing rate of AMof FCBs is found to be equal to an average value in a cycle of a cyclicmodel of contact binaries. This might suggest that the evolution of FCBsundergoes thermal relaxation oscillation (TRO) and that the coalescenceof W UMa systems is a very long process, which is also indicated by thedynamical evolution of FCBs.
| CCD Minima for Selected Eclipsing Binaries in 2007
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| Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation
Orbital angular momentum (OAM, Jo), systemic mass (M) andorbital period (P) distributions of chromospherically active binaries(CAB) and W Ursae Majoris (W UMa) systems were investigated. Thediagrams of and logJo-logM were formed from 119 CAB and 102 WUMa stars. The logJo-logM diagram is found to be mostmeaningful in demonstrating dynamical evolution of binary star orbits. Aslightly curved borderline (contact border) separating the detached andthe contact systems was discovered on the logJo-logM diagram.Since the orbital size (a) and period (P) of binaries are determined bytheir current Jo, M and mass ratio, q, the rates of OAM loss(dlogJo/dt) and mass loss (dlogM/dt) are primary parametersto determine the direction and the speed of the dynamical evolution. Adetached system becomes a contact system if its own dynamical evolutionenables it to pass the contact border on the logJo-logMdiagram. The evolution of q for a mass-losing detached system is unknownunless the mass-loss rate for each component is known. Assuming q isconstant in the first approximation and using the mean decreasing ratesof Jo and M from the kinematical ages of CAB stars, it hasbeen predicted that 11, 23 and 39 per cent of current CAB stars wouldtransform to W UMa systems if their nuclear evolution permits them tolive 2, 4 and 6 Gyr, respectively.
| The dynamical stability of W Ursae Majoris-type systems
Theoretical study indicates that a contact binary system would mergeinto a rapidly rotating single star due to tidal instability when thespin angular momentum of the system is more than a third of its orbitalangular momentum. Assuming that W Ursae Majoris (W UMa) contact binarysystems rigorously comply with the Roche geometry and the dynamicalstability limit is at a contact degree of about 70 per cent, we obtainthat W UMa systems might suffer Darwin's instability when their massratios are in a region of about 0.076-0.078 and merge into thefast-rotating stars. This suggests that the W UMa systems with massratio q <= 0.076 cannot be observed. Meanwhile, we find that theobserved W UMa systems with a mass ratio of about 0.077, correspondingto a contact degree of about 86 per cent would suffer tidal instabilityand merge into the single fast-rotating stars. This suggests that thedynamical stability limit for the observed W UMa systems is higher thanthe theoretical value, implying that the observed systems have probablysuffered the loss of angular momentum due to gravitational waveradiation (GR) or magnetic stellar wind (MSW).
| Variation in the orbital period of W UMa-type contact systems
The secular variation in the orbital period Porb is studiedas a function of the mass ratio q of the components in a sample of 73contact systems of class W UMa constructed from a survey of current(1991–2003) published photometric and spectroscopic data. Almostall the W UMa-systems (>93% of this sample) are found to have avariation in their orbital periods Porb which alternates insign independently of their division into A-and Wsubclasses. Astatistical study of this sample in terms of the observedcharacteristics dPorb/dt and q showed that on the average thenumbers of increases (35 systems) and decreases (33 systems) in theperiods are the same, which indicates the existence of flows directedalternately from one component to the other and illustrates the cyclicalcharacter of the thermal oscillations. An analysis of the behavior ofdPorb/dt as a function of the mass interval of the primarycomponent yields a more accurate value for the mass ratio, q ≈ 0.4÷ 0.45 at which contact binaries are separated into A-andW-subclasses. No correlations were observed between the fill-out factorfor the outer contact configuration, the total mass of the contactsystem, and the mass ratio of the components, on one hand, and the signof the secular variation in the period. The physical properties andevolutionary features of these systems are discussed.
| Deep, Low Mass Ratio Overcontact Binary Systems. VI. AH Cancri in the Old Open Cluster M67
CCD photometric light curves in the B and V bands obtained in 2001 andin the V band obtained in 2002 of AH Cnc in the old open cluster M67 arepresented. It is shown that AH Cnc is a total-eclipsing binary and itslight curves correspond to a typical A type according to Binnendijk'sclassification. The variations of the light curve around the primaryminimum and second maximum were found. Our nine epochs of light minimummonitored from 2001 to 2005, including others collected from theliterature, were used to create the first study of the period changes ofthe binary system. A cyclic oscillation with a period of 36.5 yr and anamplitude of 0.0237 days was discovered to be superposed on a continuousperiod increase (dP/dt=3.99×10-7 days yr-1).Weak evidence indicates that there exists another small-amplitude periodoscillation (A4=0.0035 days, P4=7.75 yr). Thesymmetric light curves in the B and V bands obtained in 2001 wereanalyzed with the 2003 version of the Wilson-Devinney code. It isconfirmed that AH Cnc is a deep overcontact binary system with a highdegree of overcontact f=58.5%+/-4.5% and a low mass ratio ofq=0.1682+/-0.0012. The existence of the third light and the cyclicperiod oscillation both may suggest that AH Cnc is a triple systemcontaining an unseen third body. The tertiary component may have playedan important role in the origin of the overcontact binary star byremoving angular momentum from the central system, which would cause itto have a short initial orbital period and thus evolve into anovercontact configuration by angular momentum loss. The long-term periodincrease can be interpreted as a mass transfer from the less massivecomponent to the more massive one. As the orbital period increases, thedecrease of the mass ratio will cause it finally to evolve into a singlerapid-rotating star when the system meets the more familiar criterionthat the orbital angular momentum be less than 3 times the total spinangular momentum. Therefore, AH Cnc may be a progenitor of the bluestraggler stars in M67.
| V781 Tauri: a W Ursae Majoris binary with decreasing period
We analyze light curves of the W UMa type eclipsing binary V781 Taurifrom three epochs and radial velocity curves from two epochssimultaneously, including previously unpublished B and V data. Theoverall time span is from 1983 to 2000 and the solution is donecoherently in time (not phase) with five light curves and two sets ofprimary and secondary velocity curves. Minor systematic differencesamong the individual light curves are not large enough to undermine thevalue of a coherent solution that represents 18 years of observations.Times of minima confirm a period of 0.34491d and the general solutionfinds a small period change, dP/P, of(5.08±{04})×10-11 that represents recentbehavior. The eclipse timings cover the last half-century and find dP/Pabout four times smaller, corresponding to a period change time scale,P/(dP/dt) of about 6 million years. The system is over-contact with afilling factor of 0.205. The solution produces a temperature differenceof about 260 K between the components, an inclination of 65.9dg, and amass ratio M_2/M_1=2.47. Separate solutions of the several light curvesthat incorporate dark spots find parameters that differ little fromcurve to curve. Absolute masses, luminosities, radii and the distanceare derived, with luminosities and distance based on star 1 being oftype G0V. The orbital angular momentum is compared with those of other WUMa type binaries and is normal. The star to star mass flow that one caninfer from dP/dt is opposite to that expected from TRO (ThermalRelaxation Oscillator) theory, but pertains to a time span that is veryshort compared to the time scale of TRO oscillations.
| New CCD Times of Minima of Eclipsing Binary Systems
We present a total of 208 CCD timings for 103 eclipsing binaries.
| BO Canum Venaticorum and SS Comae Berenices: A Photometric Study of AW UMa-Type Binaries
BO CVn and SS Com are two short-period W UMa-type binary stars withspectral types earlier than F5. In the present paper new CCD photometriclight curves in B, V, and R bands of BO CVn and the first complete lightcurve in V band of SS Com are presented. The light curves of the twobinaries are symmetric, and no variations of the light curves were foundfor both systems that are quite unlike those of cooler overcontactbinaries. These observational properties may suggest weak photosphericdark spot activity in the two systems during the observational timeintervals. Photometric solutions of the two W UMa-type binaries werederived by using the 2003 version of the Wilson-Devinney (W-D) method.The new solutions suggest that they are overcontact binary stars withdegrees of overcontact of f=40.6% for BO CVn and f=49.6% for SS Com. Ournew times of light minimum confirmed the long-time period increases ofthe two systems, and the rates of continuous period increase wererevised. The long-time period increases, the orbital periods, thedegrees of overcontact, and the mass ratios all suggest that they are onan evolutionary stage of mass transfer from the less massive componentto the more massive one, and SS Com will reach the present evolutionarystate of BO CVn. The slow evolution toward extreme mass ratio will causethem finally to coalesce to single stars. Therefore, both of them are AWUMa-type near-coalescent overcontact binary systems.
| A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
| Times of Minima for Neglected Eclipsing Binaries in 2005
Times of minima obtained at Rolling Hills Observatory during 2005 for anumber of neglected eclipsing binaries are presented.
| Precise CCD Times of Minima of Selected Eclipsing Binaries
We present 135 precise CCD minima timings for 93 eclipsing binariesobtained at Ondrejov observatory during 2003-2004.
| A ROSAT Survey of Contact Binary Stars
Contact binary stars are common variable stars that are all believed toemit relatively large fluxes of X-rays. In this work we combine a largenew sample of contact binary stars derived from the ROTSE-I telescopewith X-ray data from the ROSAT All Sky Survey (RASS) to estimate theX-ray volume emissivity of contact binary stars in the Galaxy. Weobtained X-ray fluxes for 140 contact binaries from the RASS, as well astwo additional stars observed by the XMM-Newton observatory. From thesedata we confirm the emission of X-rays from all contact binary systems,with typical luminosities of approximately 1.0×1030ergs s-1. Combining calculated luminosities with an estimatedcontact binary space density, we find that contact binaries do not havestrong enough X-ray emission to account for a significant portion of theGalactic X-ray background.
| A Catalog of 1022 Bright Contact Binary Stars
In this work we describe a large new sample of contact binary starsextracted in a uniform manner from sky patrol data taken by the ROTSE-Itelescope. Extensive ROTSE-I light-curve data are combined with J-, H-,and K-band near-infrared data taken from the Two Micron All Sky Surveyto add color information. Contact binary candidates are selected usingthe observed period-color relation. Candidates are confirmed by visualexamination of the light curves. To enhance the utility of this catalog,we derive a new J-H period-color-luminosity relation and use this toestimate distances for the entire catalog. From these distance estimateswe derive an estimated contact binary space density of(1.7+/-0.6)×10-5 pc-3.
| Photometric Investigations of Three Short-Period Binary Systems: GSC 0763-0572, RR Centauri, and ɛ Coronae Australis
CCD photometric observations of the short-period eclipsing binary GSC0763-0572 were carried out in the B and V bands at Yunnan Observatory inChina. Three light minimum times were determined from the observationsand the orbital period of this system was revised. Photometric solutionsfor three W UMa-type stars (i.e., GSC 0763-0572, RR Cen, and ɛCrA) were deduced by the 2003 version of the Wilson-Devinney code withand without third lights. All three systems are found to be A-typeeclipsing binaries with low mass ratios. Combining with theradial-velocity curves for RR Cen (King, Hilditch 1984, MNRAS, 209, 645)and ɛ CrA (Goecking, Duerbeck 1993, A&A, 278, 463), theabsolute parameters for those two binaries were redetermined. Based onall minimum times of RR Cen, it is found that the orbital period shows along-term increase superimposed on a cyclic variation. The secularchange with a rate of dP/dt = +1.21 × 10-7 dyr-1 may suggest that RR Cen is undergoing mass transfer fromthe secondary component to the primary one with dm/dt = +3.12×10-8Modot yr-1. The cyclicoscillation with a period of 65.1(±0.4)yr and an amplitude of0.0124(±0.0007) d may be explained by the presence of a thirdbody, which can be identified by the revised photometric solution. It isbelieved that if the orbital period increases for those systems is true,this kind of binary may evolve into a rapid-rotating single star.
| Deep, Low Mass Ratio Overcontact Binary Systems. IV. V410 Aurigae and XY Bootis
The complete charge-coupled device (CCD) light curves in the V, R, and Ibands for the eclipsing binary V410 Aur were observed at the YunnanObservatory in China. Four new light minimum times of V410 Aur werederived from new observations. The photometric solution for V410 Aur wasobtained for the first time, while the orbital elements for XY Boo(observed by Binnendijk in 1971) were reanalyzed by using the latestWilson-Devinney code. The third light contributions to the total lightsof the two binaries are obtained. The results reveal that both systemsare A-subtype W UMa binaries with low mass ratios and deep degrees ofovercontact (i.e., qph=0.1428 and f=52.4% for V410 Aur, andqph=0.1855 and f=55.9% for XY Boo). The photometric massratios of the two binaries are very consistent with the spectroscopicmass ratios. By combining the spectroscopic elements with ourphotometric solutions, the absolute photometric parameters for V410 Aurand XY Boo are (re)determined. Analyzing the orbital periods of the twobinaries, it is discovered that their orbital periods show continuousperiod increases, suggesting that the systems are undergoing masstransfer from the less massive component to the more massive one throughthe inner Lagrangian point L1. This kind of binary, with alow mass ratio, a deep degree of overcontact, and a continuous periodincrease, may coalesce into a rapidly rotating single star due to tidalinstability.
| 164. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
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Observation and Astrometry data
| Constellation: | Βοώτης |
| Right ascension: | 13h49m11.57s |
| Declination: | +20°11'24.6" |
| Apparent magnitude: | 10.543 |
| Proper motion RA: | -22 |
| Proper motion Dec: | 29 |
| B-T magnitude: | 10.759 |
| V-T magnitude: | 10.561 |
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