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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.
| Pulsations and apsidal motion in the eclipsing variable system DI Herculis
In 2003-2008, highly accurate photoelectric and CCD observationsof the close binary system DI Her were performed in the V band. Thelight curves of three primary and three secondary eclipses wereconstructed. These observations, along with the highly accuratephotoelectric observations of other authors obtained in different yearsfrom 1963 to 1986, have confirmed the difference between the observed(1{./o}3 ±0{./o}1/100 yr) and theoretical(4{./o}3/100 yr) rates of apsidal motion. Ourphotometric data are indicative of a possible variability in the systemwith period P' = 1.175 days and amplitude A' = 0{./ m}011, which is probably related to the pulsations of one of thecomponents. There may be a third body in the system that producesin-phase variations in the times of primary and secondary minima with aperiod of 10.5 yr and an amplitude of 1{./ m }5.
| On the apsidal motion of BP Vulpeculae
BP Vulpeculae is a bright eclipsing binary system showing apsidalmotion. It was found in an earlier study that it shows retrogradeapsidal motion which contradicts theory. In this paper we present thefirst BV light curve of the system and its light curve solution as wellas seven new times of the minima from the years 1959 1963. This way wecould expanded the baseline of the investigation to five decades. Basedon this longer baseline we concluded that the apsidal motion is progradeagreeing with the theoretical expectations and its period is about 365years and the determined internal structure constant is close to thetheoretically expected one.
| B.R.N.O. Times of minima
Not Available
| Artificial Intelligence Approach to the Determination of Physical Properties of Eclipsing Binaries. I. The EBAI Project
Achieving maximum scientific results from the overwhelming volume ofastronomical data to be acquired over the next few decades demandsnovel, fully automatic methods of data analysis. Here we concentrate oneclipsing binary (EB) stars, a prime source of astrophysicalinformation, of which only some hundreds have been rigorously analyzed,but whose numbers will reach millions in a decade. We describe theartificial neural network (ANN) approach which is able to surmount thehuman bottleneck and permit EB-based scientific yield to keep pace withfuture data rates. The ANN, following training on a sample of 33,235model light curves, outputs a set of approximate model parameters[T2/T1, (R1+R2)/a,esinω, ecosω, and sini] for each input light curve data set.The obtained parameters can then be readily passed to sophisticatedmodeling engines. We also describe a novel method polyfit forpreprocessing observational light curves before inputting their data tothe ANN and present the results and analysis of testing the approach onsynthetic data and on real data including 50 binaries from the Catalogand Atlas of Eclipsing Binaries (CALEB) database and 2580 light curvesfrom OGLE survey data. The success rate, defined by less than a 10%error in the network output parameter values, is approximately 90% forthe OGLE sample and close to 100% for the CALEB sample-sufficient for areliable statistical analysis. The code is made available to the public.Our approach is applicable to EB light curves of all classes; this firstpaper in the eclipsing binaries via artificial intelligence (EBAI)series focuses on detached EBs, which is the class most challenging forthis approach.
| Comparative statistics and origin of triple and quadruple stars
The statistics of catalogued quadruple stars consisting of two binaries(hierarchy 2 + 2), is studied in comparison with triple stars, withrespective sample sizes of 81 and 724. Seven representative quadruplesystems are discussed in greater detail. The main conclusions are asfollows. (i) Quadruple systems of ? Lyr type with similar massesand inner periods are common, in 42 per cent of the sample the outermass ratio is above 0.5 and the inner periods differ by less than 10times. (ii) The distributions of the inner periods in triple andquadruple stars are similar and bimodal. The inner mass ratios do notcorrelate with the inner periods. (iii) The statistics of outer periodsand mass ratios in triples and quadruples are different. The medianouter mass ratio in triples is 0.39 independently of the outer period,which has a smooth distribution. In contrast, the outer periods of 25per cent quadruples concentrate in the narrow range from 10 to 100yr,the outer mass ratios of these tight quadruples are above 0.6 and theirtwo inner periods are similar to each other. (iv) The outer and innermass ratios in triple and quadruple stars are not mutually correlated.In 13 per cent of quadruples both inner mass ratios are above 0.85(double twins). (v) The inner and outer orbital angular momenta andperiods in triple and quadruple systems with inner periods above 30dshow some correlation, the ratio of outer-to-inner periods is mostlycomprised between 5 and 104. In the systems with small periodratios the directions of the orbital spins are correlated, while in thesystems with large ratios they are not. The properties of multiple starsdo not correspond to the products of dynamical decay of small clusters,hence the N-body dynamics is not the dominant process of theirformation. On the other hand, rotationally driven (cascade)fragmentation possibly followed by migration of inner and/or outerorbits to shorter periods is a promising scenario to explain the originof triple and quadruple stars.
| New absolute magnitude calibrations for detached binaries
Lutz-Kelker bias corrected absolute magnitude calibrations for thedetached binary systems with main-sequence components are presented. Theabsolute magnitudes of the calibrator stars were derived at intrinsiccolours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey)photometric systems. As for the calibrator stars, 44 detached binarieswere selected from the Hipparcos catalogue, which have relative observedparallax errors smaller than 15% (σπ/π≤0.15).The calibration equations which provide the corrected absolute magnitudefor optical and near-infrared pass bands are valid for wide ranges ofcolours and absolute magnitudes: -0.18<(B-V)0<0.91,-1.6
| 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.
| 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.
| Tidal and rotational effects in the perturbations of hierarchical triple stellar systems. II. Eccentric systems - the case of AS Camelopardalis
Aims.We study the perturbations of a relatively close third star on atidally distorted eccentric eclipsing binary. We consider both theobservational consequences of the variations of the orbital elements andthe interactions of the stellar rotation with the orbital revolution inthe presence of dissipation. We concentrate mainly on the effect of ahypothetical third companion on both the real, and the observed apsidalmotion period. We investigate how the observed period derived mainlyfrom some variants of the O-C relates to the real apsidal motion period. Methods: We carried out both analytical and numerical investigationsand give the time variations of the orbital elements of the binary bothin the dynamical and the observational reference frames. We give thedirect analytical form of an eclipsing O-C affected simultaneously bythe mutual tidal forces and the gravitational interactions with atertiary. We also integrated numerically simultaneously the orbital androtational equations for the possible hierarchical triple stellar systemAS Camelopardalis. Results: We find that there is asignificant domain of the possible hierarchical triple systemconfigurations, where both the dynamical and the observational effectstend to measure longer apsidal advance rate than is expectedtheoretically. This happens when the mutual inclination of the close andthe wide orbits is large, and the orbital plane of the tertiary almostcoincides with the plane of the sky. We also obtain new numericalresults on the interaction of the orbital evolution and stellar rotationin such triplets. The most important fact is that resonances might occuras the stellar rotational rate varies during the dissipation-drivensynchronization process, for example in the case when the rotationalrate of one of the stars reaches the average Keplerian angular velocityof the orbital revolution.Appendix A is only available in electronic form at http://www.aanda.org
| Evidence for a Third Body in the Eclipsing Binary DI Herculis
Not Available
| Triple systems showing apsidal motion
Binary systems showing both apsidal motion and light travel time (LTT)effects which cause orbital period changes in close binaries werestudied. 15 triple systems showing apsidal motion were found bysearching the literature, and a table including the important parametersof these systems was constructed. Six of the systems given in this tablewere selected and observed photometrically. Existence of both apsidalmotion and LTT effects in all selected systems was investigated by meansof the analysis of their eclipse times. The mean observed internalstructure constants, log = k2,obs, and contributions to theapsidal motion from the theory of General Relativity and thethird/fourth bodies were calculated. The masses of the third/fourthbodies and some characteristics of their orbits were also calculated.
| 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
| Third-Body Parameters from Whole Light and Velocity Curves
Eclipsing binaries can improve multiple system statistics via thelight-time effect and radial velocity shifts. Here an algorithm operateson data of mixed type to exploit these opportunities. Main reasons forenhanced reliability are that (1) combined light and velocity curvesgive better timewise coverage than either type alone, (2) properlyweighted solutions impersonally balance light and velocity information,and (3) the entire theory is within the computer model, so observationsare used directly without corrections. A brief history of mixedwhole-curve solutions is given and the relative importance of light-timeand radial velocity input for third-body parameters is discussed andquantified. Period sifting by power spectral analysis is essentiallyindispensable in preliminary work. Applications are to the Algol-typesystem DM Persei and the detached system VV Orionis. An assumption ofcoplanarity for DM Per's inner and outer orbits is tested and quantifiedby dynamical experiments. Derived third-body parameters for DM Per aremainly reasonable and self-consistent. For comparison with whole-curveresults, we also investigated DM Per's ephemeris in terms of eclipsetimings and found whole-curve solutions to give smaller standard errorsin reference epoch (T0), binary orbit period (P), and dP/dt,over a similar baseline in time. An astonishing outcome is lack ofevidence that can pass reasonable validity tests for VV Ori'swell-accepted third star with P~120 days. Estimates of third light doindicate a third star, but the correct period cannot now be established,so the star cannot be identified as the one heretofore recognized fromradial velocity evidence. The much cited 120 day period appears to be anartifact of the window function for VV Ori's historical velocityobservations.
| 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.
| New Times of Minima of Eclipsing Binary Systems
We present 82 photoelectric minima observations of 34 eclipsingbinaries.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Eccentric Eclipsing Binaries: Tests of General Relativity
The study of apsidal motion in detached eclipsing binary systems witheccentric orbits is known as an important source of information forstellar internal structure as well as for the possibility ofverification of general relativity outside the Solar System. Suitableobjects for this research were collected by Giménez (1994). Inthis paper we report a summary of our results on the observationalstatus of three eccentric binaries with longer periods, namely V541Cygni, EW Orionis, and GG Orionis, and we appeal to photometrists withmoderate or small telescopes around the world to observe these binaries.
| Observational Evidence for a Third Body in AS Camelopardalis
The eclipsing variable AS Camelopardalis is a binary system with ananomalously slow apsidal motion. So far no acceptable explanation hasbeen presented for this phenomenon in the framework of classical theoryof gravitation. We observed this variable in 1981 and from 1993 to 1996.We determined the times of minima and analyzed them to reveal alight-time effect with an amplitude of 3 minutes and a period of 2.2years, thereby providing evidence for a third body in the system. Theallowance for the third-component effects may resolve the discrepancybetween the theoretical and observed rates of apsidal motion.
| Pulsations in the eclipsing variable system AS Camelopardalis
We performed photoelectric observations of AS Cam in 2002 2004. Five newtimes of minima were obtained. Their positions are consistent with thepreviously found light equation for the system and with the hypothesisthat the difference between the observed (15°/100 yr) andtheoretical (44°/100 yr) rates of apsidal motion results from thepresence of a third body in the system. A Fourier analysis of twoobservational data sets, 1968 1970 and 2002 2004, reveals, with a highsignificance, periodic light variations with a frequency of ω 0 =1.0950 ± 0.0001d-1 and an amplitude of 0 . m 020, which areprobably caused by the radial pulsations of one of the components. Wefound a seasonal phase shift of these oscillations that may be producedby other periodic processes in the system. We show that the fairly largescatter of observed times of minima about the theoretical curve of thelight equation can be explained by the presence of pulsations. Using the2002 and 2004 observations as an example, we show that including thepulsations reduces this scatter.
| New Times of Minima of Eclipsing Binary Systems and of Maximum of SXPHE Type Stars
We present 64 photoelectric minima observations of 31 eclipsingbinaries. We also report three new times of maxima of three SXPHE typepulsating stars.
| 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.
| 164. List of Timings of Minima Eclipsing Binaries by BBSAG Observers
Not Available
| Stability of Triple Star Systems with Highly Inclined Orbits
It is well established that certain detached eclipsing binary starsexhibit apsidal motions whose values are in disagreement with calculateddeviations from Keplerian motion based on tidal effects and the generaltheory of relativity. Although many theoretical scenarios have beendemonstrated to bring calculations into line with observations, all haveseemed unlikely for various reasons. In particular, it has beenestablished that the hypothesis of a third star in an orbit almostperpendicular to the orbital plane of the close binary system canexplain the anomalous motion at least in some cases. The stability oftriple star systems with highly inclined orbits has been in doubt,however. We have found conditions that allow the long-term stability ofsuch systems, so that the third-body hypothesis now seems a likelyresolution of the apsidal motion problem. We apply our stabilitycriteria to the cases of AS Cam and DI Her and recommend observations atthe new Keck interferometer, which should be able to directly observethe third bodies in these systems.
| 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.
| 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.
| Up-to-Date Linear Elements of Eclipsing Binaries
About 1800 O-C diagrams of eclipsing binaries were analyzed and up-todate linear elements were computed. The regularly updated ephemerides(as a continuation of SAC) are available only in electronic form at theInternet address: http://www.as.ap.krakow.pl/ephem/.
| Applications of the theory of the general three-body problem
The analytical theory of the general three-body problem to real triplestellar systems is applied. On the stellar systems ξ UMa, ζAqu, and AS Cam it is shown how this theory can be used for theinvestigation of the dynamical evolution of triple stellar systems. Itis possible to establish the moment of the close approach of the innerpair, and to define the secular and long-periodic perturbations in themotions of the periastrons and nodes.
| Rotating stellar models and dynamic tides in close binaries: A first approach
Rotating stellar models - homogeneous and evolved ones - were introducedfor the first time, in order to investigate the effects of rotationallyinduced changes in the internal structure of stars on the apsidal motionin close binary systems within the framework of the theory of dynamictides. The rotating models are calculated in the quasi-sphericalapproximation under the assumption that the star rotates as a solidbody. The models show that the spectrum of resonances between dynamictides and free oscillation modes is substantially modified by rotation.In particular, the changes in the internal structure of the rotatingmodels yield complex spectra which are more than simple images of thespectra in non-rotating models shifted in the period space. An immediateconsequence of the differences between rotating and non-rotating modelsis that a reconsideration of the global problem of the apsidal-motionmay be in order.
| 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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