Synchronization and circularization in early-type binaries on main sequence
We showed in a preceding paper based on an analysis of the observedrates of apsidal motion that synchronization in early-type eclipsingbinaries continues on the main sequence, and the observedsynchronization times, tsyn, agree with the Zahn's theory andare inconsistent with the shorter time-scale proposed by Tassoul. Itfollows from this that circularization in early-type binaries must alsoproceed in accordance with the Zahn's theory because the circularizationtimes, tcirc, in both theories are rather tightly related totsyn via relation tcirc ~?tsyn,where ? is the orbital-to-axial momentum ratio.To further investigate this problem, we compile a catalogue of 101eclipsing binaries with early-type main-sequence components(M1,2 > 1.6Msolar). We determine the ages, t,and circularization time-scales, tcirc, for all these systemsin terms of the two competing theories by comparing observational datawith modern models of stellar evolution of Claret and atmospheric modelsof Kurucz. We compute tcirc with the allowance for theevolutionary variations of the physical parameters of the componentsand, for the first time in such studies, also take into account thevariations of the orbital parameters (P, a, e) in the process ofcircularization subject to the conservation of the total angularmomentum.The results of these computations show that the mechanism of orbitalcircularization in early-type close binary systems (CBSs) suggested byTassoul is, like in the case of synchronization, inconsistent withobservational data. At the same time, the Zahn's mechanism, which isbased on the dissipation of the energy of dynamic tides in the upperlayers of the envelopes of CBSs components due to non-adiabaticity ofthese layers, agrees satisfactorily with observations.
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B.R.N.O. Times of minima
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Rapid apsidal motion in eccentric eclipsing binaries: OX Cassiopeia, PV Cassiopeia, and CO Lacertae
Aims.Double-lined eclipsing binaries are a traditional tool to test thecapability of the stellar evolutionary models. If such binaries showapsidal motion, it is also possible to check, in addition to theirabsolute dimensions, some aspects of their internal structure. In orderto perform this additional test, we monitored the times of a minimum ofthree eclipsing binaries with accurate absolute dimensions. Methods:Approximately thirty new precise times of minimum light recorded withCCD photometers were obtained for three early-type eccentric-orbiteclipsing binaries OX Cas (P = 2.49°, e = 0.041), PV Cas (1.75°,0.032), and CO Lac (1.54°, 0.029). O-C diagrams were analyzed by theLacy's method using all reliable timings found in the literature, andthe elements of apsidal motion were improved. On the other hand, stellarmodels computed for the precise observed masses of the three systemswere used as theoretical tools to compare with the observed shift in theperiastron position. Results: We confirm very short periods of apsidalmotion of approximately 38.2, 91.0, and 43.4 years for OX Cas, PV Cas,and CO Lac, respectively. The relativistic effects are negligible, beingup to 6% of the total apsidal motion rate in all systems. Thecorresponding observed apsidal motion rates are in good agreement withthe theoretical predictions, except for the case of PV Cas, whosecomponents seem to be more mass concentrated than the models predict.
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Mass-luminosity relation of intermediate-mass stars
The mass-luminosity relation (MLR) for intermediate-mass stars is basedon data on detached double-lined eclipsing binaries. However, there is anotable difference between the parameters of B0V-G0V components ofeclipsing binaries and those of single stars. Single early-type starsare rapid rotators, whereas tidal forces produce synchronous rotation inclose binaries and all such pairs are synchronized, so components ofclose binaries rotate more slowly. As is well known, stellar rotationchanges stellar evolution and the global parameters of a star.In this work we collect data on fundamental parameters of stars withmasses m > 1.5msolar. They are components of binaries withP > 15 d and consequently are not synchronized with the orbitalperiods and presumably are rapid rotators. These stars are believed toevolve similarly with single stars. Modern data on masses, absolute andbolometric luminosities, radii and temperatures of detachedmain-sequence double-lined eclipsing binary components (i.e. presumablyslow rotators) are also collected.Mass-luminosity, mass-temperature and mass-radius relations of close andwide binaries are presented, as well as their Hertzsprung-Russelldiagram. For the mass range 4.5 < m/msolar < 5.5 (lateB stars) it was found that rapid rotators exhibit slightly higherluminosities and larger radii than predicted by the standard relations,and their main sequence is shifted to the right-hand side with respectto that of the close binary components. The resulting relations forrapidly and slowly rotating A-F and early B stars are not statisticallydifferent.As our estimations show, for the given mass range the effect on theinitial mass function (IMF) is marginal, but there is no way to estimatethe degree to which the effect may be important for higher masses.Available observational data for m > 12msolar are too poorto make definite conclusions. Knowledge of the MLR should come fromdynamical mass determinations of visual binaries combined with spatiallyresolved precise photometry. Then the IMF should be revised for thatmass range.
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Determination of the axial rotation rate using apsidal motion for early-type eclipsing binaries
Because the modern theory of stellar structure and evolution has a soundobservational basis, we can consider that the apsidal parametersk2 computed in terms of this theory correctly reflect theradial density distribution in stars of different masses and spectraltypes. This allows us to address the problem of apsidal motion in closebinary systems in a new way. Unlike the traditional approach, in thispaper we use the observed apsidal periods Uobs to estimatethe angular axial velocities of components, ωr, atfixed model values of k2. We use this approach to analyse theobservational data for 28 eclipsing systems with known Uobsand early-type primaries (M >= 1.6 Msolar or Te>= 6000 K). We measure the age of the system in units of thesynchronization time, t/tsyn.Our analysis yielded the following results. (i) There is a clearcorrelation between ωr/ωsyn andt/tsyn: the younger a star, the higher the angular velocityof its axial rotation in units of ωsyn, the angularvelocity at pseudo-synchronization. This correlation is more significantand obvious if the synchronization time, tsyn, is computed interms of the Zahn theory. (ii) This observational fact implies that thesynchronization of early-type components in close binary systemscontinues on the main sequence. The synchronization times for the innerlayers of the components (i.e. those that are responsible for apsidalmotion) are about 1.6 and 3.1 dex longer than those predicted by thetheories of Zahn and Tassoul, respectively. The average initial angularvelocities (for the zero-age main sequence) are equal toω0/ωsyn ~ 2.0. The dependence of theparameter E2 on stellar mass probably needs to be refined inthe Zahn theory. (iii) Some components of the eclipsing systems of thesample studied show radially differential axial rotation. This isconsistent with the Zahn theory, which predicts that the synchronizationstarts at the surface, where radiative damping of dynamical tidesoccurs, and develops toward the interior. Therefore, one would expectthe inner parts of young double early-type stars to rotate faster thanthe outer parts.
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166. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
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A new catalogue of eclipsing binary stars with eccentric orbits
A new catalogue of eclipsing binary stars with eccentric orbits ispresented. The catalogue lists the physical parameters (includingapsidal motion parameters) of 124 eclipsing binaries with eccentricorbits. In addition, the catalogue also contains a list of 150 candidatesystems, about which not much is known at present.Full version of the catalogue is available online (see the SupplementaryMaterial section at the end of this paper) and in electronic form at theCDS via http://cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/MNRAS/(vol)/ (page)E-mail: ibulut@comu.edu.tr
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Effect of tidal evolution in determining the ages of eclipsing-variable early main sequence close binary systems
New Claret evolutionary model-tracks, constructed for the first time forstudying close binary systems (CBS) including tidal evolution constants,are used to determine the age of 112 eclipsing-variable stars in theSvechnikov-Perevozkina catalog by the method of isochrones. There issome interest in comparing the calculated ages with previous estimatesobtained for these same close binary systems using evolutionarymodeltracks for individual stars taking their mass loss into account. Acorrelation of the ages of the principal and secondary components isnoted, which is most marked for massive close binaries with principalcomponents having masses M1 ? 3 M?. Arejuvenating effect is found to occur for the systems studied here ascalculated on the new tracks; it is most distinct for low-mass closebinaries with a total mass M1 + M2 ? 3.5M? and is predicted theoretically in terms of magneticbraking. The calculated broadband grid of isochrones, from zero-agemain-sequence (ZAMS) to the age of the galaxy, can be used forestimating the ages of close binaries from other catalogs. Ages aregiven for the 112 eclipsing-variable close binaries with detachedcomponents lying within the main sequence.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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165. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
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Apsidal Motion of CO Lacertae
The importance of eclipsing binaries study for determination of orbitalparameters and internal stellar structure due to observed times ofminima is presented. The summary of apsidal motion theory is introduced.It is also presented the method for determination of apsidal motionparameters developed by Lacy in 1992. Iterative numerical methods areused to solve the transcendental equations to arbitrarily highprecision. We use a Levenberg-Marquardt method to obtain simultaneouslythe optimum values of fitted parameters and their mean errors. As anexample, this method is used to analyze the apsidal motion of CO Lac.The orbital parameters, as well as the internal structure constant, aredetermined and improved from the recent photoelectric observed times ofminima. It is also presented the time evolution of k2 to obtain the ageof CO Lac system and it's illustrated by means of position both of thecomponents in H-R diagram.
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Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
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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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Die 37. Tagung in BRNO.
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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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Sektion Bedeckungsveraenderliche: Lichtkurven in allen Phasen.
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Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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Close binary stars in ob-association regions i. preliminary investigation
We performed a sample of O- and B-eclipsing binary stars inOB-association regions and obtained the preliminary list of 147 binariesin 45 OB-association regions. We tried to elucidate the question whether(or not) the close binaries belong to corresponding OB-associations,from the commonness of their proper motions, radial velocities anddistances. Based on the completeness of the data,the binaries aredevided into three groups and the scheme for calculation of degree ofbelonging of stars to OB-associations is developed. Necessary data arenot available for nine systems and they are given in a specific table.For 12 cases, the binaries project onto the regions of two associations.We show that 33 (22.3%) close binary stars are members, 65 (43.9%) areprobable members and 39 (26.4%) are less probable members of theOB-associations. We find that 11 binaries belong to the Galaxybackground. The comparison of the distributions of orbital periods forthe binaries in OB-associations and for O-, B-binaries of the Galaxybackground shows their considerable differences in the vicinity of thetwo-day period.
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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.
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Photoelectric Minima of Selected Eclipsing Binaries
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Photoelectric Minimum Times of Some Eclipsing Binary Stars
We present 15 minimum times of 8 eclipsing binaries observed in theyears from 2001 to 2003 and in 1998 only for V436 Per.
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Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
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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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149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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Bedeckungsveraenderliche mit Apsidendrehung.
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Das Brunner Punktesystem.
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CCD Minima of Selected Eclipsing Binaries in 2000
This report presents minima timings of selected eclipsing binaries
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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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