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Precise Times of Minimum Light of Neglected Eclipsing Binaries
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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.
| Absolute dimensions of detached eclipsing binaries - I. The metallic-lined system WW Aurigae
WW Aurigae is a detached eclipsing binary composed of two metallic-linedA-type stars orbiting each other every 2.5 d. We have determined themasses and radii of both components to accuracies of 0.4 and 0.6 percent, respectively. From a cross-correlation analysis of high-resolutionspectra we find masses of 1.964 +/- 0.007 Msolar for theprimary star and 1.814 +/- 0.007 Msolar for the secondarystar. From an analysis of photoelectric uvby and UBV light curves wefind the radii of the stars to be 1.927 +/- 0.011 Rsolar and1.841 +/- 0.011 Rsolar, where the uncertainties have beencalculated using a Monte Carlo algorithm. Fundamental effectivetemperatures of the two stars have been derived, using the Hipparcosparallax of WW Aur and published ultraviolet, optical and infraredfluxes; these are 7960 +/- 420 and 7670 +/- 410 K. The masses, radii andeffective temperatures of WW Aur are only matched by theoreticalevolutionary models for a fractional initial metal abundance, Z, ofapproximately 0.06 and an age of roughly 90 Myr. This seems to be thehighest metal abundance inferred for a well-studied detached eclipsingbinary, but we find no evidence that it is related to the metallic-linednature of the stars. The circular orbit of WW Aur is in conflict withthe circularization time-scales of both the Tassoul and the Zahn tidaltheories and we suggest that this is due to pre-main-sequence evolutionor the presence of a circular orbit when the stars were formed.
| Aus der Sektion Bedeckungsveranderliche.
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| An Assessment of Dynamical Mass Constraints on Pre-Main-Sequence Evolutionary Tracks
We have assembled a database of stars having both masses determined frommeasured orbital dynamics and sufficient spectral and photometricinformation for their placement on a theoretical H-R diagram. Our sampleconsists of 115 low-mass (M<2.0 Msolar) stars, 27pre-main-sequence and 88 main-sequence. We use a variety of availablepre-main-sequence evolutionary calculations to test the consistency ofpredicted stellar masses with dynamically determined masses. Despitesubstantial improvements in model physics over the past decade, largesystematic discrepancies still exist between empirical and theoreticallyderived masses. For main-sequence stars, all models considered predictmasses consistent with dynamical values above 1.2 Msolar andsome models predict consistent masses at solar or slightly lower masses,but no models predict consistent masses below 0.5 Msolar,with all models systematically underpredicting such low masses by5%-20%. The failure at low masses stems from the poor match of mostmodels to the empirical main sequence below temperatures of 3800 K, atwhich molecules become the dominant source of opacity and convection isthe dominant mode of energy transport. For the pre-main-sequence samplewe find similar trends. There is generally good agreement betweenpredicted and dynamical masses above 1.2 Msolar for allmodels. Below 1.2 Msolar and down to 0.3 Msolar(the lowest mass testable), most evolutionary models systematicallyunderpredict the dynamically determined masses by 10%-30%, on average,with the Lyon group models predicting marginally consistent masses inthe mean, although with large scatter. Over all mass ranges, theusefulness of dynamical mass constraints for pre-main-sequence stars isin many cases limited by the random errors caused by poorly determinedluminosities and especially temperatures of young stars. Adopting awarmer-than-dwarf temperature scale would help reconcile the systematicpre-main-sequence offset at the lowest masses, but the case for this isnot compelling, given the similar warm offset at older ages between mostsets of tracks and the empirical main sequence. Over all age ranges, thesystematic discrepancies between track-predicted and dynamicallydetermined masses appear to be dominated by inaccuracies in thetreatment of convection and in the adopted opacities.
| Photoelectric Minima of Selected Eclipsing Binaries
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| Ein Hoch auf die Hochs Helga und Liljana.
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| Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
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| A Census of the Young Cluster IC 348
We present a new census of the stellar and substellar members of theyoung cluster IC 348. We have obtained images at I and Z for a42'×28' field encompassing the cluster andhave combined these measurements with previous optical and near-infraredphotometry. From spectroscopy of candidate cluster members appearing inthese data, we have identified 122 new members, 15 of which havespectral types of M6.5-M9, corresponding to masses of ~0.08-0.015Msolar by recent evolutionary models. The latest census forIC 348 now contains a total of 288 members, 23 of which are later thanM6 and thus are likely to be brown dwarfs. From an extinction-limitedsample of members (AV<=4) for a16'×14' field centered on the cluster, weconstruct an initial mass function (IMF) that is unbiased in mass andnearly complete for M/Msolar>=0.03 (<~M8). Inlogarithmic units where the Salpeter slope is 1.35, the mass functionfor IC 348 rises from high masses down to a solar mass, rises moreslowly down to a maximum at 0.1-0.2 Msolar, and then declinesinto the substellar regime. In comparison, the similarly derived IMF forTaurus from Briceño et al. and Luhman et al. rises quickly to apeak near 0.8 Msolar and steadily declines to lower masses.The distinctive shapes of the IMFs in IC 348 and Taurus are reflected inthe distributions of spectral types, which peak at M5 and K7,respectively. These data provide compelling, model-independent evidencefor a significant variation of the IMF with star-forming conditions.Based on observations obtained at Keck Observatory, Steward Observatory,the MMT Observatory, and the Canada-France-Hawaii Telescope. Thispublication makes use of data products from the Two Micron All SkySurvey, which is a joint project of the University of Massachusetts andthe Infrared Processing and Analysis Center/California Institute ofTechnology, funded by the National Aeronautics and Space Administrationand the National Science Foundation.
| Bedeckungsveraenderliche mit Apsidendrehung.
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| Das Brunner Punktesystem.
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| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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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.
| 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.
| uvbyβ Photometry of Selected Eclipsing Binary Stars
New uvbyβ observations of 51 eclipsing binary stars are presented,and outside-eclipse averages for 45 of them are given. Many of thesebinaries are detached main-sequence pairs that have been discovered tobe double-lined spectroscopic binaries and appear suitable fordeterminations of accurate absolute dimensions and masses. Photometricproperties are recomputed for 14 of the binaries, for which absoluteproperties have been published previously. Intercomparisons are madewith previous photometry, when available, and notes are given for someindividual systems.
| Detached double-lined eclipsing binaries as critical tests of stellar evolution. Age and metallicity determinations from the HR diagram
Detached, double-lined spectroscopic binaries that are also eclipsingprovide the most accurate determinations of stellar mass, radius,temperature and distance-independent luminosity for each of theirindividual components, and hence constitute a stringent test ofsingle-star stellar evolution theory. We compile a large sample of 60non-interacting, well-detached systems mostly with typical errorssmaller than 2% for mass and radius and smaller than 5% for effectivetemperature, and compare them with the properties predicted by stellarevolutionary tracks from a minimization method. To assess the systematicerrors introduced by a given set of tracks, we compare the resultsobtained using three widely-used independent sets of tracks, computedwith different physical ingredients (the Geneva, Padova and Granadamodels). We also test the hypothesis that the components of thesesystems are coeval and have the same metallicity, and compare thederived ages and metallicities with the ones obtained by fitting asingle isochrone to the system. Overall, there is a good agreement amongthe different determinations, and we provide a comprehensive discussionon the sub-sample of systems which either present problems or haveestimated metallicities. Although within the errors the published trackscan fit most of the systems, a large degeneracy between age andmetallicity remains. The power of the test is thus limited because themetallicities of most of the systems are unknown. The full version ofTable 6 is only available in the electronic form athttp://www.edpsciences.org
| Vitesses radiales photoélectriques de binaires àéclipses. VI. Orbites spectroscopiques et éléments physiques de 12 étoiles doubles Photoelectric radial velocities of eclipsing binaries VI. Orbital and physical elements of 12 double stars
Spectroscopic orbits of the 12 eclipsing binary systems, TW And, CD And,RS Ari, RU Cnc, TW Cnc, UU Cnc, V788 Cyg, AW Her, MM Her, RV Lib, EW Oriand ZZ UMa are obtained from Coravel and Elodie radial velocitymeasurements. We obtain a first orbit for CD And, RS Ari, TW Cnc, andV788 Cyg. For the systems TW And, RU Cnc, UU Cnc, AW Her, MM Her, RVLib, EW Ori and ZZ UMa, the new spectroscopic orbits are either betteror of quality comparable to that previously published. The physicalproperties of these systems were estimated with the photometricparameters from available data except CD And, TW Cnc, UU Cnc, V788 Cygand RV Lib for which we found a model compatible with the observations.The systems RU Cnc, AW Her, MM Her and RV Lib belong to RS CVn group. Ingeneral these systems were difficult to observe with Coravel, on the onehand because the stars are relatively weak and on the other hand becauseof nature of the components giving peaks of correlation with weakcontrast. La plupart des observations ont étéeffectuées àl'Observatoire de Haute-Provence (CNRS).Based, in part, on observations collected at the European SouthernObservatory, la Silla, Chile. La Table 1 est disponible seulement sousforme électronique au CDS via ftp à cdsarc.u-strasbg.fr(130.79.128.5) ou viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/387/850
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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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.
| Binary Masses as a Test for Pre-Main-Sequence Tracks
Observations of binaries have traditionally provided the means forascertaining stellar masses. Here we use the published data on eightpre-main-sequence pairs to gauge the accuracy of our own, recentlycalculated, evolutionary tracks. We consider both eclipsing,double-lined spectroscopic binaries, which provide the mass of each starseparately, and noneclipsing, double-lined systems, which yield only theratio. We also analyze the visual, quadruple system GG Tau, for whichthe sum of the two component masses follows from observations of thecircumbinary disk. In almost all cases, our theoretically derived massesor mass ratios are in good agreement with the empirical values. For twobinaries (NTTS 162814-2427 and P1540), the observational results arestill too uncertain for a proper comparison. We also find that thederived contraction ages within each pre-main-sequence pair are nearlyequal. This result extends earlier findings regarding visual pairs andindicates that the components of all binaries form in proximity, perhapswithin the same dense cloud core. Finally, our study reveals that theTrapezium star BM Ori is very young since both the star itself and itscompanion have contraction ages less than 105 yr.
| 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.
| 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.
| Further critical tests of stellar evolution by means of double-lined eclipsing binaries
The most accurately measured stellar masses and radii come fromdetached, double-lined eclipsing binaries, as compiled by Andersen. Wepresent a detailed quantitative comparison of these fundamental datawith evolution models for single stars computed with our evolution code,both with and without the effects of enhanced mixing or overshootingbeyond the convective cores. We use the same prescription forovershooting that Schroder, Pols & Eggleton found to reproduce theproperties of zeta Aurigae binaries. For about 80 per cent of the 49binary systems in the sample, both sets of models provide a good fit toboth stars at a single age and metallicity within the observationaluncertainties. We discuss possible causes for the discrepancies in theother systems. For only one system, AI Hya, do the enhanced-mixingmodels provide a significantly better fit to the data. For two others(WX Cep and TZ For) the fit to the enhanced-mixing models is alsobetter. None of the other systems can individually distinguish betweenthe models with and without enhanced mixing. However, the number ofsystems in a post-main-sequence phase is in much better agreement withthe enhanced-mixing models. This test provides supportive evidence forextended mixing in main-sequence stars in the range 2-3Msolar.
| Eccentric Eclipsing Binary Stars as Test of General Relativity: the Case of EW Orionis
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| Eclipse Monitoring of Eccentric Binary Systems
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| 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 Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
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Observation and Astrometry data
| Constellation: | Orion |
| Right ascension: | 05h20m09.15s |
| Declination: | +02°02'40.0" |
| Apparent magnitude: | 9.79 |
| Proper motion RA: | -4.2 |
| Proper motion Dec: | 7.2 |
| B-T magnitude: | 10.625 |
| V-T magnitude: | 9.859 |
Catalogs and designations:
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