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The most plausible explanation of the cyclic period changes in close binaries: the case of the RS CVn-type binary WW Dra
Cyclic period changes are a fairly common phenomenon in close binarysystems and are usually explained as being caused either by the magneticactivity of one or both components or by the light travel time effect(LTTE) of a third body. We searched the orbital period changes in 182EA-type (including the 101 Algol systems used by Hall), 43 EB-type and53 EW-type binaries with known mass ratio and spectral type of thesecondary component. We reproduced and improved the diagram in Hallaccording to the new collected data. Our plots do not support theconclusion derived by Hall that cyclic period changes are restricted tobinaries having a secondary component with spectral type later than F5.The presence of period changes among systems with a secondary componentof early type indicates that magnetic activity is one, but not the only,cause of the period variation. It is discovered that cyclic periodchanges, probably resulting from the presence of a third body, are morefrequent in EW-type binaries among close systems. Therefore, the mostplausible explanation of the cyclic period changes is the LTTE throughthe presence of a third body. Using the century-long historical recordof the times of light minimum, we analysed the cyclic period change inthe Algol binary WW Dra. It is found that the orbital period of thebinary shows a ~112.2-yr cyclic variation with an amplitude of ~0.1977d.The cyclic oscillation can be attributed to the LTTE by means of a thirdbody with a mass no less than 6.43Msolar. However, nospectral lines of the third body were discovered, indicating that it maybe a candidate black hole. The third body is orbiting the binary at adistance closer than 14.4 au and may play an important role in theevolution of this system.
| B.R.N.O. Contributions #34
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| 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.
| 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.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Sektion Bedeckungsveraenderliche: Lichtkurven in allen Phasen.
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| Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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| 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.
| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| FU Orionis: A Binary Star?
By using the Adaptive Optics with a Laser for Astronomy system at the3.6 m telescope of the Calar Alto Observatory, we detected a faint redstar in the apparent vicinity of FU Ori, the prototype of the FUoroutburst stars. Independent confirmation of the detection is obtainedfrom archival Probing the Universe with EnhancedOptics/Canada-France-Hawaii Telescope images. The separation between thecompanion candidate and FU Ori is 0.50", and their brightness contrastis around 4 mag. We discuss the possible nature of the newly detectedstar based on near-infrared photometry and its proper motion relative toFU Ori. The photometric data are consistent with a nearby late-typemain-sequence star, a background giant star, and a pre-main-sequencestar. On the basis of the proper motion and the stellar surface densityin the direction toward FU Ori, we argue that the probabilities of thefirst two options are very low.
| Minima of binary stars
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| The Origin of Cyclic Period Changes in Close Binaries: The Case of the Algol Binary WW Cygni
Year- to decade-long cyclic orbital period changes have been observed inseveral classes of close binary systems, including Algol, W UrsaeMajoris, and RS Canum Venaticorum systems and the cataclysmic variables.The origin of these changes is unknown, but mass loss, apsidal motion,magnetic activity, and the presence of a third body have all beenproposed. In this paper, we use new CCD observations and thecentury-long historical record of the times of primary eclipse for WWCygni to explore the cause of these period changes. WW Cyg is an Algolbinary whose orbital period undergoes a 56 yr cyclic variation with anamplitude of ~0.02 days. We consider and reject the hypotheses of masstransfer, mass loss, apsidal motion, and the gravitational influence ofan unseen companion as the cause for these changes. A model proposed byApplegate, which invokes changes in the gravitational quadrupole momentof the convective and rotating secondary star, is the most likelyexplanation of this star's orbital period changes. This finding is basedon an examination of WW Cyg's residual O-C curve and an analysis of theperiod changes seen in 66 other Algols. Variations in the gravitationalquadrupole moment are also considered to be the most likely explanationfor the cyclic period changes observed in several different types ofbinary systems.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Das Brunner Punktesystem.
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| A HIPPARCOS Census of the Nearby OB Associations
A comprehensive census of the stellar content of the OB associationswithin 1 kpc from the Sun is presented, based on Hipparcos positions,proper motions, and parallaxes. It is a key part of a long-term projectto study the formation, structure, and evolution of nearby young stellargroups and related star-forming regions. OB associations are unbound``moving groups,'' which can be detected kinematically because of theirsmall internal velocity dispersion. The nearby associations have a largeextent on the sky, which traditionally has limited astrometricmembership determination to bright stars (V<~6 mag), with spectraltypes earlier than ~B5. The Hipparcos measurements allow a majorimprovement in this situation. Moving groups are identified in theHipparcos Catalog by combining de Bruijne's refurbished convergent pointmethod with the ``Spaghetti method'' of Hoogerwerf & Aguilar.Astrometric members are listed for 12 young stellar groups, out to adistance of ~650 pc. These are the three subgroups Upper Scorpius, UpperCentaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as VelOB2, Tr 10, Col 121, Per OB2, alpha Persei (Per OB3), Cas-Tau, Lac OB1,Cep OB2, and a new group in Cepheus, designated as Cep OB6. Theselection procedure corrects the list of previously known astrometricand photometric B- and A-type members in these groups and identifiesmany new members, including a significant number of F stars, as well asevolved stars, e.g., the Wolf-Rayet stars gamma^2 Vel (WR 11) in Vel OB2and EZ CMa (WR 6) in Col 121, and the classical Cepheid delta Cep in CepOB6. Membership probabilities are given for all selected stars. MonteCarlo simulations are used to estimate the expected number of interloperfield stars. In the nearest associations, notably in Sco OB2, thelater-type members include T Tauri objects and other stars in the finalpre-main-sequence phase. This provides a firm link between the classicalhigh-mass stellar content and ongoing low-mass star formation. Detailedstudies of these 12 groups, and their relation to the surroundinginterstellar medium, will be presented elsewhere. Astrometric evidencefor moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, CamOB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive.OB associations do exist in many of these regions, but they are eitherat distances beyond ~500 pc where the Hipparcos parallaxes are oflimited use, or they have unfavorable kinematics, so that the groupproper motion does not distinguish it from the field stars in theGalactic disk. The mean distances of the well-established groups aresystematically smaller than the pre-Hipparcos photometric estimates.While part of this may be caused by the improved membership lists, arecalibration of the upper main sequence in the Hertzsprung-Russelldiagram may be called for. The mean motions display a systematicpattern, which is discussed in relation to the Gould Belt. Six of the 12detected moving groups do not appear in the classical list of nearby OBassociations. This is sometimes caused by the absence of O stars, but inother cases a previously known open cluster turns out to be (part of) anextended OB association. The number of unbound young stellar groups inthe solar neighborhood may be significantly larger than thoughtpreviously.
| 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.
| Statistical study of semi-detached and near-contact semi-detached binaries
A statistical study was made of 107 semidetached with combined lightcurve solutions. An empirical period-dependent mass-radius relation wasderived, thereby revealing the impossibility of having evolvedsemidetached systems with very short periods. Statistically, thenear-contact semidetached systems have the common properties of nearlyequal mass densities of the components, larger mass-ratios, shorterperiods and smaller specific angular momenta, and their A- F-typesecondaries generally have greater densities than the secondaries ofclassical Algol systems of the same spectral types. A detaileddiscussion is also made in this paper on the evolution of near-contactsemidetached binaries.
| Absolute parameters of stars in semidetached eclipsing binary systems
A number of questions concerning the absolute parameters of stars insemidetached binary systems are addressed. Consideration is given to:similarities between Algol-type binaries and unevolved detached binarieswith respect to the mass-luminosity law; and the single-line classicalAlgol candidates with known mass functions and photometric solutions formass ratio. It is shown that the validity of the mass luminosity-lawcannot be verified for individual Algol-type binaries though it doeshold well on average; and (2), the existence of a definite class ofsd-binaries not containing a proportion of significantly undersize typesis apparent. The conclusions are found to be in general agreement withthe observations of Hall and Neff (1979).
| A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
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| Loss of orbital angular momentum and period changes in ALGOLS
Initial values of orbital period have been computed for 50 Algolbinaries using previously published relations and then compared withobservational data. The calculations assumed an initial mass ratio of1.2, which is the average mass ratio for unevolved binaries. Thecomputed orbital period ratios are compared with the observed trend ofperiod variation in Algol-type binaries. It is concluded that theagreement between theory and observational data is much better when anonconservative approach to evolution is adopted.
| Statistics of categorized eclipsing binary systems Lightcurve shapes, periods, and spectral types
The statistics of the light curve morphologies, eclipse depths, orbitalperiods, and spectral types of about 1000 eclipsing binary systems areexamined, after attempting to subdivide these binaries into variousbasic evolutionary categories. The applicability of statisticalcriteria, based on light curve morphologies and eclipse depths, for thecategorization of eclipsing binaries has been found more limited thanpreviously believed. In particular, EW-type light curves turn out to begood indicators of contact systems (though not conversely), while EA-and EB-type light curves have little physical significance. Moreover,the study reveals a strong deficit of short-period noncontact systems inthe whole spectral range, together with an underabundance of early-typecontact binaries (compared with the number of late-type contact pairs).Interestingly, the distribution of evolved Algol-type systems isshifted, on average, to periods longer than those of unevolved detachedsystems in the OB and early A spectral range (and to shorter periods inthe F spectral range).
| Mass transfer in close binary systems - Original and remnant masses
Masses of numerous Algol binaries (and a few Wolf-Rayet systems) arecompared with new theoretical predictions in which the effect ofovershooting in stellar interiors is considered. The comparison appearsto confirm that usual mass-transfer computations cannot satisfactorilyaccount for the observed masses of the post-mass exchange remnants. Itis suggested that the incongruities which hinder a quantitativeevaluation of the amount of mass loss from close binaries may be relatedto the possible occurrence of complicated interactive processes,including phases of contact configurations, which might drasticallymodify the outcome of mass-transfer processes.
| General properties of Algol binaries
Theoretical computations on close binary evolution have made it possibleto obtain a general understanding of the evolutionary scenario of Algolvariables in terms of mass exchange. The present investigation has theobjective to draw attention to some important discrepancies between theobservational data of Algol variables and the relevant theoreticalresults. A compilation of the observed properties of 101 Algol variablesis presented. This term is used to denote binaries related to theclassical Algol variables from the evolutionary point of view. Attentionis given to the statistical properties of the binaries of the selectedsample, taking into account a comparison of the binaries with similaravailable statistical analyses of a large sample of eclipsing andspectroscopic binaries. An order-of-magnitude estimate is provided ofthe amount of mass ejected into the interstellar space by Algol binariesas a result of nonconservative mass-transfer processes.
| Some aspects of mass loss and mass transfer in Algol variables
Algol variables are examined to clarify evolutionary implications, andcheck the validity of simple models of nonconservative mass transfer.Properties of Algol variables, including the distribution of mass,radii, mass ratios, and orbital periods, are compared with statisticalanalyses of eclipsing and spectroscopic binaries. Results indicate thatas the total mass of the Algol system increases, the orbital perioddecreases, the mass ratio increases, and the secondary components becomeless prominent. Initial values of orbital periods and total mass areestimated and calculated according to conservative assumptions, althoughthe evolutionary status of 20 percent of the Algol variables could notbe accounted for using these calculations. Relatively large mass andangular momentum loss is found in several Algol variables, and case Bmass exchange is so strongly favored for variables of relatively lowmass, that no candidate for products of case A mass transfer exists.Case A is found to predominate for variables of higher total mass,although not as strongly as expected, and thus a large deficit of case Aremnant systems is observed.
| Revised Photometric Elements of Seven Sd-Systems
Abstract image available at:http://adsabs.harvard.edu/abs/1981A&AS...43..251G
| Evolution in semi-detached binary systems
The evolutionary process of semidetached binary systems is considered onthe basis of nonconservation of orbital angular momentum. Initialperiods for 54 Algol-type binaries are calculated using relations givenby Chaubey (1979) and assuming an initial mass ratio of 1.2 (the averagemass ratio for unevolved binaries). It is found that the semidetachedbinary systems follow Type B evolution.
| A catalogue of parameters for eclipsing binaries
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| Photoelectrically-Neglected Eclipsing Binaries
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Observation and Astrometry data
| Constellation: | Cepheus |
| Right ascension: | 23h52m32.93s |
| Declination: | +68°56'01.6" |
| Apparent magnitude: | 9.946 |
| Proper motion RA: | 1.3 |
| Proper motion Dec: | -10 |
| B-T magnitude: | 10.531 |
| V-T magnitude: | 9.995 |
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