Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
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Precise Times of Minimum Light of Neglected Eclipsing Binaries
Not Available
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Analysis of Van Houten's Estimates of Variable Stars From Photographic Plates
Huge amount of observations from photogrphic plates made by C. J. vanHouten remained unprocessed and unpublished after his death. The datawere obtained during the first half of the 20th century. All of thestars are situated on the southern hemisphere a most of them areeclipsing binaries. These times of minima can do a great job for O-Canalysis of these objects. The aim of this paper is to introduce thisproject.
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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.
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Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
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Times of Minimum Light of Neglected Eclipsing Binaries
Not Available
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An Apparent Descriptive Method for Judging the Synchronization of Rotation of Binary Stars
The problem of the synchronous rotation of binary stars is judged byusing a synchronous parameter Q introduced in an apparent descriptivemethod. The synchronous parameter Q is defined as the ratio of therotational period to the orbital period. The author suggests severalapparent phenomenal descriptive methods for judging the synchronizationof rotation of binary stars. The first method is applicable when theorbital inclination is well-known. The synchronous parameter is definedby using the orbital inclination i and the observable rotationalvelocity (V1,2 sin i)M. The method is mainly suitable for eclipsingbinary stars. Several others are suggested for the cases when theorbital inclination i is unknown. The synchronous parameters are definedby using a1,2 sin i,m1,2 sin3 i, the mass function f (m) andsemi-amplitudes of the velocity curve, K1,2 given in catalogue ofparameters of spectroscopic binary systems and (V1,2 sin i)M. Thesemethods are suitable for spectroscopic binary stars including those thatshow eclipses and visual binary stars concurrently. The synchronousparameters for fifty-five components in thirty binary systems arecalculated by using several methods. The numerical results are listed inTables 1 and 2. The statistical results are listed in Table 3. Inaddition, several apparent descriptive methods are discussed.
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
Not Available
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Apsidal Motion in Binaries: Rotation of the Components
A sample of 51 separated binary systems with measured apsidal periodsand rotational velocities of the components is examined. The ranges ofthe angles of inclination of the equatorial planes of the components tothe orbital plane are estimated for these systems. The observed apsidalvelocities can be explained by assuming that the axes of rotation of thestars are nonorthogonal to the orbital plane in roughly 47% of thesystems (24 of the 51) and the rotation of the components is notsynchronized with the orbital motion in roughly 59% of the systems (30of 51). Nonorthogonality and nonsynchrony are defined as deviations from90° and a synchronized angular velocity, respectively, at levels of1 or more.
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Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
Not Available
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Determination of the Ages of Close Binary Stars on the Main Sequence from Evolutionary Model Stars of Claret and Gimenez
A grid of isochrones, covering a wide range of stellar ages from thezero-age main sequence to 10 billion years, is calculated in the presentwork on the basis of the model stars of Claret and Gimenez withallowance for convective overshoot and mass loss by the components. Theages of 88 eclipsing variables on the main sequence from Andersen'scatalog and 100 chromospherically active stars from Strassmeier'scatalog are calculated with a description of the method of optimuminterpolation. Comparisons with age determinations by other authors aregiven and good agreement is established.
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Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations
A list of 62 detached binaries having reliable data on the rotation ofthe line of apsides is considered. Theoretical estimates of the rate ofapsidal motion are obtained. These estimates are compared withobservational data. It is shown that cases in which the theoreticalestimate exceeds the observed value are several times more frequent thancases in which the theoretical value is lower than the observed one.This discrepancy increases when systems with more reliable observationaldata are considered.
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New results on the apsidal-motion test to stellar structure and evolution including the effects of dynamic tides
We revised the current status of the apsidal-motion test to stellarstructure and evolution. The observational sample was increased by about50% in comparison to previous studies. Classical and relativisticsystems were analyzed simultaneously and only systems with accurateabsolute dimensions were considered. New interior models incorporatingrecent opacity tables, stellar rotation, mass loss, and moderate coreovershooting were used as theoretical tools to compare the predictedwith the observed shifts of the position of the periastron. The stellarmodels were computed for the precise observed masses and the adoptedchemical compositions are consistent with the corresponding tables ofopacities to avoid the inherent problems of interpolation in mass and in(X, Z). The derived chemical composition for each individual system wasused to infer the primordial helium content as well as a law ofenrichment. The values found are in good agreement with those obtainedfrom various independent sources. For the first time, the effects ofdynamic tides are taken into account systematically to determine thecontribution of the tidal distortion to the predicted apsidal-motionrate. The deviations between the apsidal-motion rates resulting from theclassical formula and those determined by taking into account theeffects of dynamic tides are presented as a function of the level ofsynchronism. For systems close to synchronisation, dynamic tides causedeviations with respect to the classical apsidal-motion formula due tothe effects of the compressibility of the stellar fluid. For systemswith higher rotational angular velocities, additional deviations due toresonances arise when the forcing frequencies of the dynamic tides comeinto the range of the free oscillation modes of the component stars. Theresulting comparison shows a good agreement between the observed andtheoretical apsidal-motion rates. No systematic effects in the sensethat models are less mass concentrated than real stars and nocorrelations with the evolutionary status of the systems were detected.
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Studies of Intermediate-Mass Stellar Models Using Eclipsing Binaries
Evolutionary computations for intermediate-mass stars are analyzed usingobserved parameters for eclipsing SB2 binaries and theoreticalparameters based on evolutionary tracks. Modern observations cannot beused to distinguish between models with and without convectiveovershooting for stars in the vicinity of the main sequence.Statistically significant discrepancies between the observed andcomputed stellar parameters are associated with systematic errors inphotometric effective temperatures. After taking into account systematiceffects, the theoretical computations fit the observational datauniformly well throughout the entire mass interval studied. Empiricaland semiempirical (i.e., reduced to the ZAMS and with solar elementalabundances) formulas for the mass-luminosity, mass-effectivetemperature, and mass-radius relations are proposed.
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Age and Metallicity Estimates for Moderate-Mass Stars in Eclipsing Binaries
We estimate the ages and metallicities for the components of 43 binarysystems using a compilation of accurate observational data on eclipsingbinaries for which lines of both components are visible in theirspectra, together with two independent modern sets of stellar evolutionmodels computed for a wide range of masses and chemical abundances. Theuncertainties of the resulting values are computed, and their stabilityis demonstrated. The ages and metallicity are compared with thosederived in other studies using different methods, as well as withindependent estimates from photometric observations and observations ofclusters. These comparisons con firm the reliability of our ageestimates. The resulting metallicities depend significantly on thechoice of theoretical model. Comparison with independent estimatesfavors the estimates based on the evolutionary tracks of the Genevagroup.
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The post-Newtonian effects due to rotation of stars on the variation of orbital elements of the component in binary system
The author examined continuously the post-Newtonian effects due torotation of stars on the variation of the orbital elements for thecomponent in binary system in PPN formalism. The secular and periodicperturbation effects are both given. The results show that there existonly the periodic variations in semi-major axis and eccentricity, andexist the periodic and secular variations in longitude of periastron andmean anomaly of epoch. In addition, the author applied the obtainedresults to calculate the post-Newtonian effects of rotation to sixbinary stars (EK Cep?GT Cep?NY Cep?V448 Cyg?V1143 Cyg?V451 Oph)on thevariation of the Orbital elements of components and discussed. Thenumerical results are given in Tablel-3. It shows that thepost-Newtonian effect caused by the two rapid rotating massivecomponents is not negligible.
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Apsidal motion in eccentric eclipsing binaries: TV Ceti and V451 Ophiuchi
Several new times of minimum light recorded with photoelectric meanshave been gathered for two bright eccentric eclipsing binaries TV Cet (P= 9fd1 , e = 0.055) and V451 Oph (P = 2fd2 , e = 0.013). Analysis of allavailable eclipse timings of TV Ceti has revealed a small motion of theline of apsides of dot ω = 0.000 30 +/- 0.000 08 degcycle-1, corresponding to an apsidal period of U = 30 000 +/-8 000 years. The contribution from the general relativity effects isdominant (dot ωrel/dot ω ~ 80 % ). In thissystem, the third body on an eccentric orbit with a period of 28.5 yearsis also predicted. The more precise values for the apsidal motionelements were computed for V451 Oph, where apsidal motion with a periodof 170 +/- 5 years was confirmed. The corresponding internal structureconstants log k2 were derived. Some of the observationsreported in this paper were obtained at the South Africa AstronomicalObservatory, Sutherland, South Africa.
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Determination of the consistent and interdependent values of the basic characteristics of eclipsing variable systems components
An approximate approach for determining consistent and interdependentwith each other principal characteristics as well as the equatorialrotational velocity and the inclination angle of rotation axis of arotator to the line - of - sight for components of eclipsing variablesystems is suggested.
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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
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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.
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Absolute Dimensions of the Unevolved B-Type Eclipsing Binary GG Orionis
We present photometric observations in B and V, as well as spectroscopicobservations of the detached, eccentric 6.6 day double-lined eclipsingbinary GG Ori, a member of the Orion OB1 association. Absolutedimensions of the components, which are virtually identical, aredetermined to high accuracy (better than 1% in the masses and betterthan 2% in the radii) for the purpose of testing various aspects oftheoretical modeling. We obtain MA=2.342+/-0.016Msolar and RA=1.852+/-0.025 Rsolar forthe primary, and MB=2.338+/-0.017 Msolar andRB=1.830+/-0.025 Rsolar for the secondary. Theeffective temperature of both stars is 9950+/-200 K, corresponding to aspectral type of B9.5. GG Ori is very close to the zero-age mainsequence, and comparison with current stellar evolution models givesages of 65-82 Myr or 7.7 Myr, depending on whether the system isconsidered to be burning hydrogen on the main sequence or still in thefinal stages of pre-main-sequence contraction. Good agreement is foundin both scenarios for a composition close to solar. We have detectedapsidal motion in the binary at a rate of ω=0.00061d+/-0.00025dcycle-1, corresponding to an apsidal period ofU=10,700+/-4500 yr. A substantial fraction of this (~70%) is due to thecontribution from general relativity, and our measurement is entirelyconsistent with theory. The eccentric orbit of GG Ori is well explainedby tidal evolution models, but both theory and our measurements of therotational velocity of the components are as yet inconclusive as towhether the stars are synchronized with the orbital motion. Some of theobservations reported here were obtained with the Multiple MirrorTelescope, a joint facility of the Smithsonian Institution and theUniversity of Arizona.
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Chemical composition of eclipsing binaries: a new approach to the helium-to-metal enrichment ratio
The chemical enrichment law Y(Z) is studied by using detacheddouble-lined eclipsing binaries with accurate absolute dimensions andeffective temperatures. A sample of 50 suitable systems was collectedfrom the literature, and their effective temperatures were carefullyre-determined. The chemical composition of each of the systems wasobtained by comparison with stellar evolutionary models, under theassumption that they should fit an isochrone to the observed propertiesof the components. Evolutionary models covering a wide grid in Z and Ywere adopted for our study. An algorithm was developed for searching thebest-fitting chemical composition (and the age) for the systems, basedon the minimization of a χ2 function. The errors (andbiases) of these parameters were estimated by means of Monte Carlosimulations, with special care put on the correlations existing betweenthe errors of both components. In order to check the physicalconsistency of the results, we compared our metallicity values withempirical determinations, obtaining excellent coherence. Theindependently derived Z and Y values yielded a determination of thechemical enrichment law via weighted linear least-squares fit. Our valueof the slope, ΔY/ΔZ=2.2+/-0.8, is in good agreement withrecent results, but it has a smaller formal error and it is free ofsystematic effects. Linear extrapolation of the enrichment law to zerometals leads to an estimation of the primordial helium abundance ofYp=0.225+/-0.013, possibly affected by systematics in theeffective temperature determination.
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Estimating the ages of eclipsing variable DM-stars on the basis of the evolutionary star models by Maeder and Meynet
A set of isochrones covering a wide range of star ages from5\cdot106 to 1010 yr was built on the basis of thestellar models by A. Maeder and G. Meynet with overshooting and massloss for Population I stars with abundances (X, Y, Z) = 0.70, 0.28,0.02. The isochrones were used to compute the ages of 88 eclipsingvariable stars from the catalog by Andersen which lie on the mainsequence. The influence of initial data errors on the rezultes wasinvestigated. The ages derived are in good agreement with the results ofother authors.
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Do the physical properties of Ap binaries depend on their orbital elements?
We reveal sufficient evidence that the physical characteristics of Apstars are related to binarity. The Ap star peculiarity [represented bythe Δ(V1-G) value and magnetic field strength] diminishes witheccentricity, and it may also increase with orbital period(Porb). This pattern, however, does not hold for largeorbital periods. A striking gap that occurs in the orbital perioddistribution of Ap binaries at 160-600d might well mark a discontinuityin the above-mentioned behaviour. There is also an interestingindication that the Ap star eccentricities are relatively lower thanthose of corresponding B9-A2 normal binaries for Porb>10d.All this gives serious support to the pioneering idea of Abt &Snowden concerning a possible interplay between the magnetism of Apstars and their binarity. Nevertheless, we argue instead in favour ofanother mechanism, namely that it is binarity that affects magnetism andnot the opposite, and suggest the presence of a newmagnetohydrodynamical mechanism induced by the stellar companion andstretching to surprisingly large Porb.
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Apsidal Motion in Double Stars. I. Catalog
A catalog of 128 double stars with measured periods of apsidal motion iscompiled. Besides the apsidal periods, the orbital elements of binariesand physical parameters of components (masses, radii, effectivetemperatures, surface gravities) are given. The agreement of the apsidalperiods found by various authors is discussed.
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Metallicity-dependent effective temperature determination for eclipsing binaries from synthetic UVBY Strömgren photometry
Strömgren synthetic photometry from an empirically calibrated gridof stellar atmosphere models has been used to derive the effectivetemperature of each component of double lined spectroscopic (SB2)eclipsing binaries. For this purpose, we have selected a sub-sample of20 SB2s for which (b-y), m_1, and c_1 individual indices are available.This new determination of effective temperature has been performed in ahomogeneous way for all these stars. As the effective temperaturedetermination is related to the assumed metallicity, we exploresimultaneous solutions in the ({{T_eff}},{[Fe/H]})-plane and present ourresults as confidence regions computed to match the observed values ofsurface gravity, (b-y), m_1, and c_1, taking into account interstellarreddening. These confidence regions show that previous estimates of{{T_eff}} are often too optimistic, and that {[Fe/H]} should not beneglected in such determinations. Comparisons with Ribas et al. (1998)using Hipparcos parallaxes are also presented for 8 binaries of ourworking sample, showing good agreement with the most reliableparallaxes. This point gives a significant weight to the validity of theBaSeL models for synthetic photometry applications.
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Orbital circularization in detached binaries with early-type primaries
Extending our previous study, the present paper reports on thediscussion of the orbital circularization in 37 detached binaries withearly-type primaries. From comparison of the theoretical predictionswith the orbital eccentricities of our binary systems, we find thatZahn's circularization theories are substantially consistent with theobserved data for overwhelming majority of our samples. However, we alsonote that three binaries of whom both components are asynchronizedrotators possess circular orbits. How to understand the circularism ofthe three systems remains a problem not only to Zahn's theories, but toall other present circularization mechanisms.We think that studies onthe circularization of pre-main-sequence binary systems could providesome clues for the problem.
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The apsidal motion test of stellar structure in relativistic systems.
We have compared observational data of apsidal motion rates forrelativistic eclipsing binaries with theoretical predictions based onstellar theoretical models. Ten double-lined eclipsing binaries withhigh quality light curves and radial velocities were selected. Theanalysis of the data available indicate that the predictions by theGeneral Relativity and the new stellar models are able to explain theshift in the periastron position. The two versions of thenon-symmetrical theory of gravitation were also investigated. The earlyversion of this theory (Moffat, 1984ApJ...287L..77M) is not supportedwhen contrasted with recent observational data since it predicts tooslow apsidal motion rates. The more recent version (Moffat,1989PhRvD..39..474M) presents several problems in its formulation, liketoo many degrees of freedom and some parameters for which there is nosevere physical constraint. Moreover, such a theory is not able topredict a priori the apsidal motion rates.
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Photometric versus empirical surface gravities of eclipsing binaries.
Systematic differences in photometric stellar surface gravitydetermination are studied by means of the comparison with empiricalvalues derived from detached double-lined eclipsing binaries.Photometric gravities were computed using Moon & Dworetsky(1985MNRAS.217..305M) grids based on Kurucz (1979ApJS...40....1K)atmosphere models, and empirical gravities were taken from Andersen(1991A&ARv...3...91A). Individual Stroemgren colours and βindices of each component of the binary system have to be taken intoaccount to correctly analyze the observed differences. A compilation ofdata on a sample containing 30 detached double-lined eclipsing binarieswith accurate (=~1-2%) determination of mass and radius and availableuvbyHbeta_ photometric data is also presented. Correction ofthe differences in terms of T_eff_ and logg for the range11000K
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Absolute dimensions of eclipsing binaries. XXI. V906 Scorpii: a triple system member of M 7.
We present an analysis based on new uvby light curves and spectroscopicdata of the detached triple-lined B-type eclipsing binary V906 Sco. Theuvby light curves are analysed with an extended version of theWilson-Devinney program. The spectroscopic CCD observations are analysedwith both the Sterne and the Lehmann-Filhes methods. We conclude fromthe combined analysis that the triple system V906 Sco is a member of theopen cluster M 7 and that its B-type eclipsing components are still onthe main sequence, at an age of (2.4+/-0.3)x10^8^yrs, already close tothe TAMS (especially the more massive one). The system is older than thetime for circularization of the orbit, and the small eccentricity isprobably caused by the third component, which, however, is unlikely tobe the main responsible for the apsidal motion, probably more influencedby tidal and rotational deformation. We determine absolute dimensions ofhigh precision (errors <2%): M_A_=3.25+/-0.07, R_A_=3.52+/-0.04,M_B_=3.38+/-0.07 and R_B_=4.52+/-0.04, in solar units. The system isdetached, with both components in synchronous rotation, and thereforerepresentative for normal stars.
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INHABITED SKY
