Precise Times of Minimum Light of Neglected Eclipsing Binaries
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New CCD Times of Minima of Eclipsing Binary Systems
We present a total of 208 CCD timings for 103 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.
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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.
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The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
A sample of bright contact binary stars (W UMa type or EW, and related:with β Lyr light curves, EB, and ellipsoidal, ELL-in effect, allbut the detached, EA) to the limit of Vmax=7.5 mag is deemedto include all discoverable short-period (P<1 day) binaries withphotometric variation larger than about 0.05 mag. Of the 32 systems inthe final sample, 11 systems have been discovered by the Hipparcossatellite. The combined spatial density is evaluated at(1.02+/-0.24)×10-5 pc-3. The relativefrequency of occurrence (RFO), defined in relation to the main-sequencestars, depends on the luminosity. An assumption of RFO~=1/500 forMV>+1.5 is consistent with the data, although the numberstatistics is poor with the resulting uncertainty in the spatial densityand the RFO by a factor of about 2. The RFO rapidly decreases forbrighter binaries to a level of 1/5000 for MV<+1.5 and to1/30,000 for MV<+0.5. The high RFO of 1/130, previouslydetermined from the deep OGLE-I sample of disk population W UMa typesystems toward Baade's window, is inconsistent with and unconfirmed bythe new results. Possible reasons for the large discrepancy arediscussed. They include several observational effects but also apossibility of a genuine increase in the contact-binary density in thecentral parts of the Galaxy. Based on data from the Hipparcos satellitemission and from the David Dunlap Observatory, University of Toronto.
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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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Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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Do the physical properties of Ap binaries depend on their orbital elements?
We reveal sufficient evidence that the physical characteristics of Apstars are related to binarity. The Ap star peculiarity [represented bythe Δ(V1-G) value and magnetic field strength] diminishes witheccentricity, and it may also increase with orbital period(Porb). This pattern, however, does not hold for largeorbital periods. A striking gap that occurs in the orbital perioddistribution of Ap binaries at 160-600d might well mark a discontinuityin the above-mentioned behaviour. There is also an interestingindication that the Ap star eccentricities are relatively lower thanthose of corresponding B9-A2 normal binaries for Porb>10d.All this gives serious support to the pioneering idea of Abt &Snowden concerning a possible interplay between the magnetism of Apstars and their binarity. Nevertheless, we argue instead in favour ofanother mechanism, namely that it is binarity that affects magnetism andnot the opposite, and suggest the presence of a newmagnetohydrodynamical mechanism induced by the stellar companion andstretching to surprisingly large Porb.
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Photoelectric and CCD times of minima of 19 eclipsing binary systems
We present several photoelectric and unfiltered CCD minima observationsof 19 eclipsing binaries. Most of them are apsidal motion stars (or atleast candidate ones).
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Interaction of Eclipsing Binaries with their Environment
The interaction of eclipsing binary star systems with the mass around(in the form of star, planet, envelope or disk) affects the orbitalperiod of these systems. Thus, the long-term orbital period changes ofeclipsing binaries which can be deduced by using the observed times ofeclipse minima provide a good tool in understanding the interaction ofeclipsing binaries with their environment. In the present contributionmany examples of the orbital period changes of different eclipsingbinaries are presented and interpreted in terms of the interaction withtheir environment.
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The calculation of critical rotational periods in three typical close binary systems based on synchronization theory.
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Photoelectric minima of 30 eclipsing binary systems
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Measurement and study of rotation in close binary stars (III) Statistical analysis of synchronization.
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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.
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Measurement and analysis of rotation in close binaries. II. Calculation of synchronism.
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Determination of Times of Minima for the Eclipsing Binary GK CEP
The star CK Cep is an eclipsing binary of the W UMa type. This star wasstudied on several nights from October, 1993, to January, 1994, as partof an undergraduate research experience program at the University ofNorth Texas Astronomy Observatory. Measurements were made using an OptecSSP-3 solid state photometer. Several new determinations of times ofprimary minima are reported. These newly measured minima together withminima reported by others in the literature were studied for systematicvariations in O-C residuals. A periodic fluctuation with period 19.9years was observed in the O-C residuals. The light elements for GK Cepwere revised and a revised ephemeris equation is proposed for predictingfuture minima.
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On the orbital period changes in contact binaries
Period changes of such complex structures as contact binaries, areconnected with the action of individual physical mechanisms and thestability properties of these systems. In order to get information aboutthese processes, we present a new simple method which can give us theobserved values of a period and its rate of change for any cycle E, ifan O-C diagram is given. Due to their strong coupling, any periodvariation in a contact binary implies underlying geometrical andstructural changes, which can be described mathematically through asystem of four differential equations. The equations are developed onthe assumption of conservation of total mass and total angular momentum.Their solution can give us (among other quantities) the required rate ofmass transfer between components, in order to satisfy the commonequipotential surface condition, at any time.
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Measurement and Analysis of Rotation in Close Binary Stars - Part One - Observations and Results
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Period changes of early-type eclipsing binaries
Eclipsing binaries with short periods are an important source of ourknowledge about the evolution of close binary systems. New photoelectrictimings of minima of the five short period early-type eclipsing binariesEG Cep, GK Cep, GO Cyg, V836 Cyg, and V1073 Cyg are presented here.Their period changes and current light elements are discussed.
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A period study of GK Cephei
A period study of the times of minima from 1900 to 1988, of a W UMasystem GK Cep was performed. The system was found to have no significantsecular period change, but the photoelectric observations reveal ashort-term periodic oscillation of the photometric period with anamplitude of about 0.035 day around the mean value of P = 0.9361653 day.Such oscillation of the photometric period has been discussed in termsof (1) the magnetically induced deformations in the atmosphere, (2) massmotions in the core of a computer star, (3) cyclic behavior in the masstransfer or mass loss rate, and (4) the light time effect due to a thirdbody in the system. It was shown that the hypothetical third body couldbe an FOV star, which is about 2.5 m fainter than GK Cep, and only 0.01arcsec away from it. The magnetic activity may not be the responsiblemechanism for the observed cyclic period variation, because the systemconsists of two early A spectral-type components probably with noconvective envelopes.
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Ultraviolet light curves of V535 Arae
The light curve of V535 Ara is determined from observations of thislong-period W UMa binary in the UV, and its gravity darkening isestimated. The UV colors and spectral type correspond to (B - V)0 =0.24, or A8V, and imply that the star should have very little residualconvection in its envelope. It is concluded that the gravity darkeningis large, as in a radiative star, unless it is modified by circulationin the common envelope, or unless all stars this warm are convective.Four solutions are obtained to a combination of optical and UV lightcurves, two for high radiative gravity darkening, and two for lowconvective gravity darkening. The light curves were fitted equally wellin all four cases, while in all but the one with low-gravity darkeningand a hot inner face there was a rather large global temperaturedifference between the two stars. It is suggested that the W UMabinaries are found only at spectral types later than about A8 becausetheir outer envelopes must be convective to transfer luminosity.
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The eclipsing binary GK Cephei - New BV photoelectric observations and light curves analysis
New B and V photoelectric observations of the eclipsing binary GK Cep(BV 382) obtained during 1987 and 1988 at the Kryonerion AstronomicalStation of the National Observatory of Athens, Greece, are presented.The corresponding light curves are analyzed using Frequency Domaintechniques to yield the geometric and photometric elements of thesystem. These elements are used together with some other physicalparameters of GK Cep to obtain calculated light curves. A final improvedset of elements, obtained from the optimal curve fitting, is given. TheO-C diagram of GK Cep indicates that its period has increased. Thesystem is found to be evolved and will soon come into contact becomingan OO Aql system.
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Close binaries observed polarimetrically
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Photoelectric Minima Times of GK Cephei and Variations in its Period
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Period changes of early-type contact binary GK Cepehei.
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Angular momenta in binary systems
The correlations of angular momenta L to masses M are studied fordifferent types of spectroscopic binaries. Postulates about equivalentstates of angular momenta for different orbital parameters areintroduced. From comparisons with galaxies and single stars, it isevidenced that there is not a unique universal function L = AM exp b,when the finite structure of the relation is analyzed: each object hasits own coefficients A, b. It seems that there are an upper and a lowerlimit for all the possible functions.
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The early spectral type contact binary systems.
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Photoelectric Minima of Eclipsing Binaries
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Polarization in contact binaries
Contact binaries represent the most abundant class of objects amongclose binaries, but they have been observed with modern polarimeters toonly a meager extent. The history of these observations is reviewed anddata referring to a previously unobserved star are summarized. It isshown that there exists some systematics among the small signalsdisplayed by these systems. The most direct understanding of the resultsleads to recognition of a distribution of scatterers which is asymmetricwith respect to the orbital plane. It is inferred that scattering ofphotospheric radiation from an asymmetric, systemic corona is the sourceof the signals.
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Eclipsing Binaries - Cancer to Corona Borealis in 1972-1984
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INHABITED SKY
