Visual Minima Timings of Eclipsing Binaries Observed in the Years 1992 - 1996
The paper contains a list of 283 new times of minima and 77 revisedtimes of minima for 63 eclipsing binaries derived by the author fromhis visual observations.
|
Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
|
165. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
Not Available
|
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.
|
Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.
Not Available
|
Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
|
Photoelectric Minima of Some Eclipsing Binary Stars
We present 70 minima times of 35 eclipsing binaries.
|
Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
Not Available
|
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 Minimum Times of Some Eclipsing Binary Stars
We present 20 minima times of 8 eclipsing binaries.
|
Up-to-date UBV light and O-C curves analyses of the eclipsing binary V477 Cygni
New and complete UBV light curves and times of minimum are presented forthe Algol-type eclipsing binary V477 Cygni (Sp. A3 V+F5 V, mv=8.5, P=2.347 days). The binary orbit of the system is highly eccentricand the system shows an apsidal motion. Using the Wilson-Devinneymethod, two photometric models, without (MODEL A) and with (MODEL B)third-body light contribution to the total light of the system, areobtained. Period analysis also gives some slender evidence for theunseen third-body in the system with the orbital period of about 157years. In the MODEL A approximation the apsidal motion period isobtained to be 371 years while it is about 434 years in the MODEL Bapproximation. The photometric mass ratio (q ~ 0.75) is in goodagreement with the spectroscopic value given by Popper(\cite{Popper1968}). The masses we obtained are 1.80+/-0.10Msun and 1.35+/-0.08 Msun and the radii are1.60+/-0.03 Rsun and 1.42+/-0.03 Rsun for theprimary and secondary components, respectively. Absolute dimensions havebeen compared with the models using a moderate amount of convectiveovershooting and mass loss given by Claret & Giménez(\cite{Claret1991}). In the log M - log R diagram both components arelocated above but close to the ZAMS. It is possible to say from the logTe - log L diagram that the secondary component is justcoming to the main sequence while the primary is slightly evolved fromthe ZAMS. The theoretical evolutionary models give an age of6.4*E8 yrs for the system.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.73.128.5) or via http:/ /cdsweb.u-strasbg.fr /cgi-bin/qcat?J/A+A/409/959
|
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.
|
New Times of Minima of Eclipsing Binary Systems
We present 58 photoelectric minima observations of 19 eclipsingbinaries.
|
Zur qualitat der visuellen Beobachtung kurzperiodisch Veranderlicher.
Not Available
|
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
|
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.
|
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.
|
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.
|
149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
Not Available
|
Bedeckungsveraenderliche mit Apsidendrehung.
Not Available
|
Das Brunner Punktesystem.
Not Available
|
Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
|
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.
|
Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
|
Times of Minima of Eclipsing Binaries
Not Available
|
The Change in the Inclination Angle of the Noneclipsing Binary SS Lacertae: Future Eclipses
Eclipses in the 14.4 day-period double-lined binary SS Lac were observedphotographically and visually early in the twentieth century but stoppedsome 50 or 60 yr ago. This has been explained by the presence of adistant third star in the system, which has now been detectedspectroscopically, with a period of 679 days. The plane of the orbit ofthe binary is changing relative to the line of sight in response toperturbations from this third object. A recent analysis by Milone et al.of all photometric material available for the system, including aremeasurement of original Harvard plates, has confirmed earlier reportsof changes in the depth of the eclipses as a function of time, which aredue to the third star. In this paper we discuss our detailed analysis ofthe eclipse amplitude measurements and extract from them information onthe change in the inclination angle of the binary over the last century.Our use of a much improved ephemeris for the system by Torres &Stefanik was found to be crucial, and it prompted us to redetermine allthe amplitudes from the historical data at our disposal, including theHarvard material used by Milone et al. Systematically lower measurementson the branches of the minima were properly accounted for, and we madeuse of both a linear approximation to the time variation of theinclination angle and a more realistic model based on the theory ofthree-body interactions (``regression of the nodes'' effect). The nodalcycle is found to be ~600 yr, within which two eclipse ``seasons''occur, each lasting about 100 yr. The noneclipsing status of the systemis expected to continue until the beginning of the twenty-third century.
|
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
|
Photoelectric Minima of Selected Eclipsing Binaries and New Elements for Several Stars
Not Available
|
Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
|
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.
|
