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Testing gravitational theories using eccentric eclipsing detached binaries
In this paper, we compare the effects of different theories ofgravitation on the apsidal motion of a sample of eccentric eclipsingdetached binary stars. The comparison is performed by using theformalism of the post-Newtonian parametrization to calculate thetheoretical advance at periastron and compare it to the observed one,after having considered the effects of the structure and rotation of theinvolved stars.A variance analysis on the results of this comparison shows that nosignificant difference can be found due to the effect of the differenttheories under test with respect to the standard general relativity(GR). It will be possible to observe differences, as we would expect, bychecking the observed period variation on a much larger lapse of time.It can also be noted from our results that f(R) theory is the nearest toGR with respect to the other tested theories.
| Recent Minima of 146 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinarySection. Times of minima from observations made from October 2010 thruMarch 2011, along with a few unpublished times of minima from olderdata, are presented.
| Random forest automated supervised classification of Hipparcos periodic variable stars
We present an evaluation of the performance of an automatedclassification of the Hipparcos periodic variable stars into 26 types.The sub-sample with the most reliable variability types available in theliterature is used to train supervised algorithms to characterize thetype dependencies on a number of attributes. The most useful attributesevaluated with the random forest methodology include, in decreasingorder of importance, the period, the amplitude, the V-I colour index,the absolute magnitude, the residual around the folded light-curvemodel, the magnitude distribution skewness and the amplitude of thesecond harmonic of the Fourier series model relative to that of thefundamental frequency. Random forests and a multi-stage scheme involvingBayesian network and Gaussian mixture methods lead to statisticallyequivalent results. In standard 10-fold cross-validation (CV)experiments, the rate of correct classification is between 90 and 100per cent, depending on the variability type. The main mis-classificationcases, up to a rate of about 10 per cent, arise due to confusion betweenSPB and ACV blue variables and between eclipsing binaries, ellipsoidalvariables and other variability types. Our training set and thepredicted types for the other Hipparcos periodic stars are availableonline.
| Recent CCD Minima of 185 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing Binarysection. Times of minima from observations made from September 2009through February 2010 are presented.
| 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.
| Relativistic apsidal motion in eccentric eclipsing binaries
Context. The study of apsidal motion in detached eclipsing binarysystems is known to be an important source of information about stellarinternal structure as well as the possibility of verifying of GeneralRelativity outside the Solar System. Aims: As part of thelong-term Ond?ejov and Ostrava observational projects, we aim tomeasure precise times of minima for eccentric eclipsing binaries, neededfor the accurate determination of apsidal motion, providing a suitabletest of the effects of General Relativity. Methods: About seventynew times of minimum light recorded with photoelectric or CCDphotometers were obtained for ten eccentric-orbit eclipsing binarieswith significant relativistic apsidal motion. Their O-C diagrams wereanalysed using all reliable timings found in the literature, and new orimproved elements of apsidal motion were obtained. Results: Weconfirm very long periods of apsidal motion for all systems. For BF Draand V1094 Tau, we present the first apsidal-motion solution. Therelativistic effects are dominant, representing up to 100% of the totalobservable apsidal-motion rate in several systems. The theoretical andobserved values of the internal structure constant k 2 werecompared for systems with lower relativistic contribution. Using thelight-time effect solution, we predict a faint third component for V1094Tau orbiting with a short period of about 8 years.Partly based on photoelectric observations secured at the HvarObservatory, Faculty of Geodesy, Zagreb, Croatia, in October 2008.
| The Spectral-type Limits of the Barr Effect
The Barr Effect is a nonrandom distribution of longitudes of periastron,ω, in spectroscopic binary orbits. Physically one would not expectelliptical binary orbits to show any preferred orientations. Aitken andStruve have shown a preference for 0<ω<90° among 275elliptical binary orbits of all primary types. Some eclipsing binariesshow inconsistencies between their light and velocity curves. Struveshowed that the velocity curves of some spectroscopic binaries aredistorted by absorption in gaseous streams flowing between thecomponents. I wondered about the occurrence of this effect for stars ofvarious spectral types and found that the effect occurs primarily forB0-B3 V-lll primaries but may be present in a few of the remaining BAstars. The B0-B3 region is also where the mean radial velocities ofstars (single plus binaries) in open clusters are systematically largerthan for other stars.
| Recent Minima of 154 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinaryCommittee. Times of minima from observations made from September 2008through February 2009 are presented.
| Recent Minima of 184 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinaryCommittee. Times of minima from observations made from March 2008through August 2008 are presented.
| Recent Minima of 155 Eclipsing Binary Stars
The AAVSO's publication of times of minima for eclipsing binary stars has shifted from the recent publication series, Observed Minima Timings of Eclipsing Binaries, Number 1-12, back to the JAAVSO. Times of minima fromobservations made in the past eight months are presented. New lightelements for AC CMi have been calculated from recent AAVSO observations:Min(JD) = 2451978.7504 + 0.867216691 E± 0.0004 ± 0.00000024
| 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.
| 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
| 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.
| Precise Times of Minimum Light of Neglected Eclipsing Binaries
Not Available
| The Case for Third Bodies as the Cause of Period Changes in Selected Algol Systems
Many eclipsing binary star systems show long-term variations in theirorbital periods, evident in their O-C (observed minus calculated period)diagrams. With data from the Robotic Optical Transient Search Experiment(ROTSE-I) compiled in the SkyDOT database, New Mexico State University 1m data, and recent American Association of Variable Star Observers(AAVSO) data, we revisit Borkovits and Hegedüs's best-casecandidates for third-body effects in eclipsing binaries: AB And, TV Cas,XX Cep, and AK Her. We also examine the possibility of a third bodyorbiting Y Cam. Our new data support their suggestion that a third bodyis present in all systems except AK Her, as is revealed by thesinusoidal variations of the O-C residuals. Our new data suggest that athird body alone cannot explain the variations seen in the O-C residualsof AK Her. We also provide a table of 143 eclipsing binary systems thathave historical AAVSO O-C data with new values computed from the SkyDOTdatabase.
| Apsidal motion in eccentric eclipsing binaries: CW Cephei, V478 Cygni, AG Persei, and IQ Persei
Aims.About thirty new times of minimum light recorded with photoelectricor CCD photometers were obtained for four early-type eccentric-orbiteclipsing binaries CW Cep (P=2.73d, e=0.029), V478 Cyg ( 2.88d, 0.016),AG Per ( 2.03d, 0.071), and IQ Per ( 1.74d, 0.076). Methods:.Their O-C diagrams were analysed using all reliable timings found inthe literature, and elements of apsidal motion were improved.Results: .We confirm relatively short periods of apsidal motion of about46, 27, 76, and 124 years for CW Cep, V478 Cyg, AG Per, and IQ Per,respectively. The corresponding internal structure constants, log k_2,are then found to be -2.12, -2.25, -2.15, and -2.36, under theassumption that the component stars rotate pseudosynchronously. Therelativistic effects are negligible, being up to 8% of the total apsidalmotion rate in all systems. Using the light-time effect solution, wehave predicted a faint third component orbiting with a period of about39 years for CW Cep.
| RW Lacertae: a New Photometric Triple Star
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.
| Apsidal motion in southern eccentric eclipsing binaries: V539 Ara, GG Lup, V526 Sgr and AO Vel
Several new times of minimum light have been observed photoelectricalyfor the early-type double-lined eccentric eclipsing binaries V539 Ara (P= 3.2 deg, e = 0.05), GG Lup (1.9 deg, 0.15), V526 Sgr (1.9 deg, 0.22)and AO Vel (1.6 deg, 0.07). The O{-}C diagrams are analysed using allreliable timings found in the literature and improved values for theelements of the apsidal motion are computed. We find more precise,relatively short periods of apsidal motion of about 162, 102, 155 and 54years for V539 Ara, GG Lup, V526 Sgr and AO Vel, respectively. Thecorresponding internal structure constants, log k_2, are then found tobe 2.33, 2.16, 2.36 and 2.24 under the assumption that the componentstars rotate pseudosynchronously. The relativistic effects arenegligible, being about 6 7% of the total apsidal motion rate in allsystems. Using the light-time effect solution, for V539 Ara we havefound a third component orbiting with a period of about 42 years, for AOVel we confirmed the third body with an orbital period of 33 years.
| 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/.
| A new photometric study of CW Cephei and its apsidal motion
New photoelectric observations of the eccentric orbit binary CW Cepheihave been carried out in B, V and R colours during the 2000 observingseason at TÜBITAK (The Scientific and Technical Research Council ofTurkey) National Observatory. The light curves of the system wereanalyzed with a nonsynchronous rotation approach using the method ofWilson-Devinney in B, V and R bands, simultaneously. Especially, we usedthe R band to check for a third light in the solution as distinct fromprevious studies. But, the third light contribution in the light curvescomes out to be almost negligible. In this study, the values of thelongitude of periastron (ω) of the system's orbit found in thesolutions of the light curves and radial velocity curves were collectedand the variation of ω with time was investigated. A new value ofthe apsidal motion velocity has been obtained as \dot{ω}=0.0582± 0.0011 (deg/cycle), corresponding to an apsidal period U=46± 1 yr.
| Catalogue of Algol type binary stars
A catalogue of (411) Algol-type (semi-detached) binary stars ispresented in the form of five separate tables of information. Thecatalogue has developed from an earlier version by including more recentinformation and an improved layout. A sixth table lists (1872) candidateAlgols, about which fewer details are known at present. Some issuesrelating to the classification and interpretation of Algol-like binariesare also discussed.Catalogue is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/417/263
| Archive of Photometric Plates Obtained at Cluj Astronomical Observatory
The archive of photometric plates obtained at the AstronomicalObservatory of Cluj in the period 1952-1974 is presented. The plateinventory is made within the framework of the Wide-Field Plate Databaseproject. The plates were taken in the regions around 110 variable stars(eclipsing variables and RR Lyrae-type stars), as well as in somecomparison stars regions.
| 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.
| 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.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
Not Available
| Das Brunner Punktesystem.
Not Available
| 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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