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Photoelectric Minima of Some Eclipsing Binary Stars
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| Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple 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.
| Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation
We study the kinematics of 129 W UMa binaries and we discuss itsimplications on the contact binary evolution. The sample is found to beheterogeneous in the velocity space. That is, kinematically younger andolder contact binaries exist in the sample. A kinematically young (0.5Gyr) subsample (moving group) is formed by selecting the systems thatsatisfy the kinematical criteria of moving groups. After removing thepossible moving group members and the systems that are known to bemembers of open clusters, the rest of the sample is called the fieldcontact binary (FCB) group. The FCB group is further divided into fourgroups according to the orbital period ranges. Then, a correlation isfound in the sense that shorter-period less-massive systems have largervelocity dispersions than the longer-period more-massive systems.Dispersions in the velocity space indicate a 5.47-Gyr kinematical agefor the FCB group. Compared with the field chromospherically activebinaries (CABs), presumably detached binary progenitors of the contactsystems, the FCB group appears to be 1.61 Gyr older. Assuming anequilibrium in the formation and destruction of CAB and W UMa systems inthe Galaxy, this age difference is treated as an empirically deducedlifetime of the contact stage. Because the kinematical ages (3.21, 3.51,7.14 and 8.89 Gyr) of the four subgroups of the FCB group are muchlonger than the 1.61-Gyr lifetime of the contact stage, the pre-contactstages of the FCB group must dominantly be producing the largedispersions. The kinematically young (0.5 Gyr) moving group covers thesame total mass, period and spectral ranges as the FCB group. However,the very young age of this group does not leave enough room forpre-contact stages, and thus it is most likely that these systems wereformed in the beginning of the main sequence or during thepre-main-sequence contraction phase, either by a fission process or mostprobably by fast spiralling in of two components in a common envelope.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Precise CCD Times of Minima of Selected Eclipsing Binaries
We present 50 CCD minima timings for 42 eclipsing binaries obtained atOndrejov observatory during 2002-2003.
| Photoelectric Minima of Some Eclipsing Binary Stars
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| Deep, Low Mass Ratio Overcontact Binary Systems. III. CU Tauri and TV Muscae
New CCD photometric light curves in the B and V bands of the neglected WUMa-type eclipsing variable star CU Tauri are presented. The O'Connelleffect in the V light curve obtained in 2001 by Yang and Liu was aboutΔV=+0.015, but it vanished in our 2004 observations. Thevariations in the levels of both minima were seen. Our two epochs oflight minimum and others compiled from the literature were used for theperiod study. It is shown that the types of some eclipse times wereincorrect and the values of the period obtained by previousinvestigators were aliases that prevented formation of a plausible O-Ccurve. A new linear ephemeris was derived, and it is discovered that theorbital period of CU Tau shows a continuous decrease at a rate ofdP/dt=-1.81×10-6 days yr-1. The presentsymmetric light curves were solved with the 2003 version of theWilson-Devinney (W-D) code. Both our solutions and those derived by Yangand Liu reveal that CU Tau is a deep (f=50.1%+/-3.2%), low mass ratio(q=0.1770+/-0.0017) overcontact binary system.Meanwhile, the photoelectric light curves in the B, V, R, and I bands ofTV Muscae published by Hilditch and coworkers were reanalyzed with the2003 version of the W-D code. It is shown that the low mass ratio binaryturns out to be a deep overcontact system with f=74.3%+/-11.3%. A periodanalysis with all collected times of light minimum revealed acombination of a long-term period decrease(dP/dt=-2.16×10-7 days yr-1) and a possiblecyclic change with a period of 29.1 yr. The rapid long-term perioddecreases of both systems can be explained as a combination of the masstransfer from the more massive component to the less massive one and theangular momentum loss due to mass outflow from the L2 point. In thatway, the overcontact degrees of the two systems will become deeper astheir periods decrease, and finally they will evolve into a singlerapid-rotation star. However, for CU Tau, the rate of the secular perioddecrease is very large when compared with the other systems of the sametype. This suggests that the long-term period decrease may be part of along-period periodic change, which we need more data to check.
| CCD Times of Minima of Selected Eclipsing Binaries
682 CCD minima observations of 259 eclipsing binaries made mainly byauthor are presented. The observed stars were chosen mainly fromcatalogue BRKA of observing programme of BRNO-Variable Star Section ofCAS.
| On the properties of contact binary stars
We have compiled a catalogue of light curve solutions of contact binarystars. It contains the results of 159 light curve solutions. Theproperties of contact binary stars were studied using the cataloguedata. As is well known since Lucy's (\cite{Lucy68a},b) and Mochnacki's(\cite{Mochnacki81}) studies, primary components transfer their ownenergy to the secondary star via the common envelope around the twostars. This transfer was parameterized by a transfer parameter (ratio ofthe observed and intrinsic luminosities of the primary star). We provethat this transfer parameter is a simple function of the mass andluminosity ratios. We introduced a new type of contact binary stars: Hsubtype systems which have a large mass ratio (q>0.72). These systemsshow behaviour in the luminosity ratio- transfer parameter diagram thatis very different from that of other systems and according to ourresults the energy transfer rate is less efficient in them than in othertypes of contact binary stars. We also show that different types ofcontact binaries have well defined locations on the mass ratio -luminosity ratio diagram. Several contact binary systems do not followLucy's relation (L2/L1 =(M2/M1)0.92). No strict mass ratio -luminosity ratio relation of contact binary stars exists.Tables 2 and 3 are available in electronic form athttp://www.edpsciences.org
| A CCD photometric study of the W UMa contact binary Y Sextantis
A V light curve of the W UMa contact binary Y Sex is presented inthis paper. From the observations, two times of minimum light wasdetermined and from the present times of minimum light and thosecollected from the references, the change in the orbital period of thesystem was analyzed with the method of Kalimeris et al. [A&A 282(1994) 775]. The result reveals that the orbital period of the systemoscillates with a cycle of about 50 years and an amplitude of1.1×10-6 days. The light curve was analyzed by means ofthe latest version of the Wilson-Devinney code, which was also used tocorrect photometric effects on the radial-velocity curve obtained byMcLean and Hilditch [MNRAS 203 (1983) 1]. The results suggest that Y Sex is an A-subtypecontact binary with a mass ratio of q=0.180(2). In the new photometricsolution, a positive value of the third light of the system suggeststhat the sinusoidal variation of the period could be caused by a thirdcomponent in the system. The absolute dimensions of Y Sex are found tobe: M1=1.21(18) Msolar, M2=0.22(3)Msolar, R1=1.50(2) Rsolar,R2=0.75(1) Rsolar, L1=3.00(44)Lsolar, L2=0.69(10) Lsolar, A=2.66(11)Rsolar.
| Catalogue of the field contact binary stars
A catalogue of 361 galactic contact binaries is presented. Listedcontact binaries are divided into five groups according to the type andquality of the available observations and parameters. For all systemsthe ephemeris for the primary minimum, minimum and maximum visualbrightness and equatorial coordinates are given. If available,photometric elements, (m1+m2)sin3i,spectral type, parallax and magnitude of the O'Connell effect are alsogiven. Photometric data for several systems are augmented by newobservations. The quality of the available data is assessed and systemsrequiring modern light-curve solutions are selected. Selectedstatistical properties of the collected data are discussed.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Period behavior of the W Ursae Majoris contact binary AH Tauri
New timing of minimum light determined from CCD observations of the WUMa type contact binary AH Tau is presented. From the present time ofminimum light and those collected from the literature, the changes inthe orbital period of the system are analyzed. The result reveals thatthe orbital period of AH Tau continuously decreased at a rate of (Deltap)/p=-1.4*E-11 from 1944 to 1976 and suddenly and sharplydecreased by about 0.33 s around 1976. After 1976 the orbital period ofthe system continually increased at a change rate of frac (Deltap)/p=1.5*E-10. A possible explanation of the changes in theorbital period of AH Tau is discussed. They may be the result ofcompound action of three mechanisms: the cyclical magnetic activity, themass loss and the radius swelling of the two components of the system.
| Period Studies of Some Neglected Close Binaries: EP Andromedae, V724 Aquilae, SS Comae, AM Eridani, FZ Orionis, BY Pegasi, EQ Tauri, and NO Vulpeculae
Orbital period changes of eight neglected short-period close binaries,EP And, V724 Aql, SS Com, AM Eri, FZ Ori, BY Peg, EQ Tau, and NO Vul,are presented based on the analysis of their O-C observations. It isfound that the periods of BY Peg and EQ Tau are decreasing at rates ofdP/dt=-1.67×10-7 and -1.72×10-7 dayyr-1, respectively, while the orbital periods of SS Com andAM Eri show secular increase at rates ofdP/dt=+5.91×10-7 and +4.39×10-7 dayyr-1. Weak evidence also indicates that the orbital period ofEP And is increasing. For FZ Ori, the decrease rate of orbital period isrevised. For the other two systems, V724 Aql and NO Vul, their O-C curvecan be described by a sudden period decrease or a continuous perioddecrease; further investigation is needed. The period changes of theeight systems can be explained by mass transfer between the twocomponents and/or mass and angular momentum loss from these binaries. Astrong mass-radius relation for observed contact binaries is formedbased on the parameters given by Maceroni & Van't Veer. It is shownthat the parameters of SS Com and EQ Tau given by Brancewicz &Dworak do not agree with the mass-radius relation. This may suggest thatthe two systems are not yet in contact. In order to understand thephysical properties of these binaries, complete photoelectric or CCDlight curves and radial velocity observations are needed.
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| Possible Mass and Angular Momentum Loss in Algol-Type Binaries. III. TU Cancri, FZ Delphini, AY Geminorum, VZ Leonis, FH Orionis, IU Persei, XZ Persei, and BE Vulpeculae
Orbital period variations of eight Algol-type binaries, TU Cnc, FZ Del,AY Gem, VZ Leo, FH Ori, IU Per, XZ Per, and BE Vul, are studied based onthe analysis of the O-C observations. It is discovered that the periodsof three systems, TU Cnc, FH Ori, and IU Per, show secular decrease. ForAY Gem and XZ Per, the orbital periods can be described by a suddendecrease or by two sudden changes superposed on a secular decrease. Weakevidence also shows that the orbital periods of the other three systems,FZ Del, VZ Leo, and BE Vul, are decreasing. As in other systems proposedby Qian, the decrease in the orbital periods of these systems, combinedwith their semidetached configurations, suggests that they may beundergoing secular mass and angular momentum loss due to magneticbraking. The irregular period jumps superposed on the secular decrease(e.g., in AY Gem, FH Ori, XZ Per, and BE Vul) can be explained byvariable magnetic coupling and gravity coupling between the twocomponents. However, the present secular period decrease of thesesystems may be part of a long-period periodic change (as in TT Del),which needs further investigation.
| ROSAT all-sky survey of W Ursae Majoris stars and the problem of supersaturation
From ROSAT all-sky survey (RASS) data we obtained X-ray fluxes for 57 WUMa type contact systems. In our sample we detected three stars whichare the shortest period main sequence binaries ever found as X-raysources. For stars with (B-V)_0 < 0.6 the normalized X-ray fluxdecreases with a decreasing color index but for (B-V)_0 > 0.6 aplateau is reached, similar to the saturation level observed for single,rapidly rotating stars. The X-ray flux of W UMa stars is about 4-5 timesweaker than that of the fastest rotating single stars. Because earlytype, low activity variables have longer periods, an apparentperiod-activity relation is seen among our stars, while cool stars with(B-V)_0 > 0.6 and rotation periods between 0.23 and 0.45 days do notshow any such relation. The lower X-ray emission of the single, ultrafast rotators (UFRs) and W UMa stars is interpreted as the result of adecreased coronal filling factor. The physical mechanisms responsiblefor the decreased surface coverage differs for UFRs and W UMa systems.For UFRs we propose strong polar updrafts within a convection zone,driven by nonuniform heating from below. The updrafts should beaccompanied by large scale poleward flows near the bottom of theconvective layer and equatorward flows in the surface layers. The flowsdrag dynamo generated fields toward the poles and create a field-freeequatorial region with a width depending on the stellar rotation rate.For W UMa stars we propose that a large scale horizontal flow embracingboth stars will prevent the magnetic field from producing long-livedstructures filled with hot X-ray emitting plasma. The decreased activityof the fastest rotating UFRs increases the angular momentum loss timescale of stars in a supersaturated state. Thus the existence of a periodcutoff and a limiting mass of W UMa stars can be naturally explained.
| Period changes in W UMa-type eclipsing binaries: DK Cygni, V401 Cygni, AD Phoenicis and Y Sextantis
We present a period analysis of the four well-known W UMa-type eclipsingbinaries DK Cyg (P = 0fd47 ), V401 Cyg (0fd58 ), AD Phe (0fd38 ) and YSex (0fd42 ). Several new times of minimum light, recordedphotoelectrically, have been gathered. Analysis of all available eclipsetimings of the DK Cygni and V401 Cygni has confirmed a significantincrease in period of 1.15 10-10 and 1.48 10-10day cycle-1, respectively. A simultaneous solution of the B,V and R light curves was computed for V401 Cyg using the Binary Maker2.0 synthetic lightcurve software. This solution indicates that V401 Cygis in contact with a filing factor of 46%. The period of AD Phe seems tobe constant. Period changes of Y Sex could be explain by a light-timeeffect caused by a third body in an eccentric orbit with a period of 58years. Some of the observations reported in this paper were obtained atthe South Africa Astronomical Observatory, Sutherland, South Africa.
| Orbital period studies of the two contact binaries TZ Bootis and Y Sextantis
The physical properties of the two A-type contact binaries TZ Boo and YSex are nearly the same. In the present paper, many of their publishedtimes of light minima are collected and the changes in their orbitalperiods are analyzed. It is indicated that the orbital period of TZ Booshows several alternating jumps while it undergoes a secular decrease of-11.8x10-8 days/year. Several random jumps superposed on asecular decrease (-5.5x10-8 days/year) are also found in theperiod of Y Sex. The secular decrease is usually interpreted as masstransfer from the more to the less massive components, or mass andangular momentum loss (AML) from the systems. According to the AMLtheory, on the contact stage, the orbital AML is mainly caused by themass transfer from the less to the more massive component and the massratio decreasing and orbital period gradually increasing are thecorresponding results. The extremely low mass ratio and orbital angularmomentum of the two systems show that they are evolved via AML and thepresent secular decrease in the periods may suggest that the magneticactivity in the two systems are very strong. The relation between thechanges of the orbital periods and the magnetic activity in the twosystems are discussed. We think that the interplay between the variableAML and variable magnetic coupling can explain both the jumps andsecular decrease in the orbital periods of the two systems. Table~2 andTable~4 are only available in electronic form at the CDS via anonymousftp to cdsarc.u-strabg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Are Contact Binaries Undergoing Thermal Relaxation Oscillations with Contact Discontinuity?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110..782W&db_key=AST
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| The thermal relaxation oscillation states of contact binaries
A contact system almost certainly cannot exist in a state of staticequilibrium undergoing periodic thermal relaxation oscillation (TRO). Inthis paper the TRO evidence is found by the calculation of 22 contactsystems: A-sub and W-sub types are in expanding and contracting TROstates at the velocities of 25.04 and 3.10 m/yr, respectively. It ispointed out that the W-phenomenon is phase-dependent and correspondingto the contracting TRO phase. The corrected period-color diagram impliesthat the two kind systems have the same physical structure.
| The interaction between the secondary and the common convective envelope in a contact binary
It has been suggested that a contact system almost certainly cannotexist in static equilibrium undergoing periodic thermal relaxationoscillation. The energy transfer in a common convective envelope (CCE)makes the secondary have a complex structure, so the interaction betweenthe secondary and CCE may play an important role in the structure andevolution of the contact system. The present paper tests the ThermalRelaxation Oscillation (TRO) theory and investigates this interactionwith polytropic stellar model from the observational datum of 22 contactsystems directly. It shows that the A-type systems are expanding with avelocity of 25.04 m/yr, and the W-type systems are contracting atvelocity of 3.10 m/yr by the calculations about these contact systems.Also, we calculate the ratio of energy transfer and the interactioncoefficient for them. The HS (hot secondary) model is supported by ourcalculations. These results may help to understand the TRO theory andthe W-phenomenon.
| Observations and period studies of two neglected W UMa systems - V401 Cygni and Y Sextantis
Photoelectric timings of minima, obtained at KPNO, are reported for theshort-period eclipsing variables V401 Cygni and Y Sextantis and adiscussion of period variations is given based on all the material. V401Cyg may be one of the few W UMa systems which exhibits a continuous,monotonic increase of the period. The period of Y Sex has beendecreasing since the discovery of the variable, with the decreaseoccurring almost certainly in two abrupt changes.
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