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The Case for Third Bodies as the Cause of Period Changes in Selected Algol Systems
Many eclipsing binary star systems show long-term variations in theirorbital periods, evident in their O-C (observed minus calculated period)diagrams. With data from the Robotic Optical Transient Search Experiment(ROTSE-I) compiled in the SkyDOT database, New Mexico State University 1m data, and recent American Association of Variable Star Observers(AAVSO) data, we revisit Borkovits and Hegedüs's best-casecandidates for third-body effects in eclipsing binaries: AB And, TV Cas,XX Cep, and AK Her. We also examine the possibility of a third bodyorbiting Y Cam. Our new data support their suggestion that a third bodyis present in all systems except AK Her, as is revealed by thesinusoidal variations of the O-C residuals. Our new data suggest that athird body alone cannot explain the variations seen in the O-C residualsof AK Her. We also provide a table of 143 eclipsing binary systems thathave historical AAVSO O-C data with new values computed from the SkyDOTdatabase.
| 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.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Some Eclipsing Binary Stars
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| 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
| CCD Minima for Selected Eclipsing Binaries in 2003
Not Available
| 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.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Radio emission from Algol-type binaries. I. Results of 1992-1993 VLA survey
In this paper we report on a 5 GHz survey of 26 Algol-type binaries. Sixsystems were detected. We combine the new results with previouslypublished data to derive some radio characteristics of Algols and tocompare them with those of other active binaries. The radio detectionrate of 30 %, a factor that is somewhat smaller compared to the case ofRSCVn-type, does not seem to be due to a reduced coronal activity. Infact, Algols share many similarities with the radio behavior of RS CVnsand the 5 GHz luminosity functions of both kind of systems look quitesimilar. Among the different possibilities, the high radio variabilityand distances, which, on average, are larger than those of RS CVns, seemto be the most reasonable explanation for the apparently reducedactivity at radio wavelengths.
| A Spectroscopic Survey of Late F--K Eclipsing Binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..106..133P&db_key=AST
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
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| UBV photometry of selected eclipsing binary stars
The study reports new UBV observations of 69 eclipsing binary stars andprovides outside-eclipse averages. Revised photometric properties offive of the binaries, for which absolute properties were publishedpreviously, are computed. Comparisons are made with previous photometry,when available, and notes are given for some individual systems.
| Reversals of mass transfer in Algol binaries
The evolution through case A mass transfer is computed for close binarysystems with masses 3 and 5 solar masses and periods in the range0.7-1.6 days. It is found that, due to mass accretion, the companionstar evolves faster, and reversed mass transfer occurs. If such areversed phase starts after core hydrogen exhaustion of the gainer(A1B2), it is driven by the rapid expansion of the latter componentduring hydrogen shell burning.
| 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.
| Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
Not Available
| A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
| A study of the O'Connell effect in the light curves of eclipsing binaries
In the present consideration of O'Connell's (1951) study of the lightcurve asymmetry between outside eclipse maxima, using UBV photoelectricdata, parametric and nonparametric methods indicate significantcorrelations in at least one color between the size of the asymmetry, onthe one hand, and several additional parameters. These include: thecolor index of the asymmetry, the relative sizes of the hotter andsmaller components, and their distortion, the relative separation of thestars, and the logarithm of the period. The present study data arecharacterized by lower mean amplitudes and a much more even distributionof the asymmetry, with respect to sign, than that of O'Connell, andthere is a tendency for the brighter maximum to be redder, contrary toO'Connell's results. More than one mechanism for the O'Connell effect issuggested.
| 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).
| 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.
| Mass loss and mass transfer in ALGOLS - A check on some current theoretical views
Abstract image available at:http://adsabs.harvard.edu/abs/1980A&A....83..217M
| A catalogue of parameters for eclipsing binaries
Not Available
| A catalogue of modern lightcurve synthesis photometric solutions of close binary systems
Not Available
| Revised photometric elements of seven R CMa systems
Photometric light curves of seven R CMa binaries are analyzed by usingWood's (1972) WINK computer model in order to obtain homogeneousphotometric elements to combine with spectroscopic results. The systemsstudied are R CMa, S Equ, RW Gem, AL Gem, T LMi, XZ Sgr, and S Vel. AnH-R diagram, a mass-luminosity relation, and a mass-radius relation areplotted for these seven systems, and mass ratios are derived from thephotometric solutions. The results indicate that all the systems exceptS Vel can be considered normal sd systems and that the R CMa-typeclassification may be retained only for S Vel, whose anomalies are basedon very doubtful spectroscopic elements. Some properties of theindividual systems are briefly reviewed. It is concluded that there isno strong evidence to support the existence of a homogeneous group of RCMa systems.
| Absolute dimensions for 32 previously suspected sd-d and R CMa-type eclipsing binaries
Not Available
| MK classifications of some Northern Hemisphere binary systems
Not Available
| Strömgren four-colour observations of Northern Hemisphere binary systems
Not Available
| The radiative interaction and evolution of medium- and low-mass binaries.
Abstract image available at:http://adsabs.harvard.edu/abs/1973AJ.....78..410K
| The light variation and orbital elements of RW Coronae Borealis.
Abstract image available at:http://adsabs.harvard.edu/abs/1972AJ.....77..239B
| Beobachtungsergebnisse der Berliner Arbeitsgemeinschaft für veränderliche Sterne e. V. (BAV)
Not Available
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Osservazione e dati astrometrici
| Costellazione: | Gemelli |
| Ascensione retta: | 06h57m38.56s |
| Declinazione: | +20°53'32.5" |
| Magnitudine apparente: | 9.895 |
| Moto proprio RA: | 1.4 |
| Moto proprio Dec: | -12.3 |
| B-T magnitude: | 10.377 |
| V-T magnitude: | 9.935 |
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