VZ CVn: a close binary system with γ Doradus-like variations
We present new photometric two-colour observations of the double-linedclose binary star VZ CVn. Combining two data sets obtained in 1971-72and in 2006, the physical parameters of both components were derived.After removing the light variations due to the eclipses and proximityeffects, a periodic variation in the more massive component with adominant period of 1.06876 d could be detected in the first photometricdata set. In accordance with its position on the Hertzsprung-Russelldiagram and both its pulsation period and pulsation constant of 0.62 d,the primary component of VZ CVn should be an excellent γ Doraduscandidate. The less massive secondary component seems to have smallerradius with respect to its mass. Both components appear to have lowerluminosities with respect to their masses; hence, their radiativeproperties seem to be different. The evolutionary status of thecomponents is also discussed.
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Modelling eclipsing binaries with pulsating components: Phase dependence of observed pulsation amplitudes
We investigate the phase dependence of the light variations due topulsations, as modulated with light variations due to the eclipses. Thestudy is based, both on a simplified model and on the rigorous lightcurve (LC) synthesis software of Wilson and Devinney. We model AB Cas asa prototype, using both of these approaches. The phase dependence of thedifferential light variations for total systems is also discussed .
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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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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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Evolution of Close Binary Systems
We collect data on the masses, radii, etc., of three classes of closebinary stars: low-temperature contact binaries (LTCBs), near-contactbinaries (NCBs), and detached close binaries (DCBs). We restrictourselves to systems in which (1) both components are, at leastarguably, near the main sequence, (2) the periods are less than a day,and (3) there is both spectroscopic and photometric analysis leading toreasonably reliable data. We discuss the possible evolutionaryconnections between these three classes, emphasizing the roles played bymass loss and angular momentum loss in rapidly rotating cool stars. Wedescribe a new mechanism, differential rotation as observed in the Sun,which can explain the remarkable efficiency of heat transport in theouter envelopes of contact binaries.
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Catalogue of the orbital elements, masses, and luminosities for short-periodic RS CVn-type eclipsing systems
New data on the orbital elements, masses, and luminosities werecollected for 31 pre-contact binary systems of short-periodic {RS}{CVn}-type. We treat the catalogued data statistically in order toaccurately define the properties and evolutionary status of each classsystem. The ages of pre-contact systems were estimated by the isochronemethod. Numerous comments and bibliographic references to the catalogueare also included.
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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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CA II H&K survey of Gamma Doradus candidates
In an investigation of the starspot hypothesis as it applies to the'slowly variable' F-type dwarfs, we spectroscopically observed eightpromising Gamma Doradus candidates to search for Ca II H&K emission. Wefound that there are no significant emission reversals in the cores ofthese resonance lines. Based on the ceiling flux calculations of the CaII K line and on calculations of the Rossby number, we conclude thatthere is no support for the presence of strong magnetic activity and thestarspot hypothesis in these objects.
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Observational data reduction of the stellar photoelectric photometry.
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Near-Contact Binary Systems in the ROSAT All-Sky Survey
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..951S&db_key=AST
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A List of Variable Stars Similar to gamma Dor
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New Photoelectric Light Curves of VZ Canum Venaticorum
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Near-contact binaries
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The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
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Program of Parallax Measurements from Space for the Nearest Eclipsing Binaries
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VZ Canum Venaticorum and AI Hydrae, detached F type binaries with variable components
Spectographic observations of VZ CVn and AI Hya are combined withpublished photometric analyses to establish the properties of thecomponents of these early-F type binaries, both of which show intrinsicphotometric variability. The variability of AI Hya has been shown to beprobably of the Delta Scuti type, so that the determination of its massand other fundamental properties is of special interest. Both componentsof AI Hya have evolved out of the main-sequence band. The intrinsicvariability of VZ CVn is of longer timescale, but its nature has notbeen established. The components of this short-period system have aunique anomaly in that both are too cool for their masses and radii andfall below the range of known luminosities for stars of their mass.
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Photoelectric Minima of Eclipsing Binaries
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The List of the Nearest and Bright Eclipsing Binaries from the HIPPARCOS Program
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A study of the O'Connell effect in the light curves of eclipsing binaries
In the present consideration of O'Connell's (1951) study of the lightcurve asymmetry between outside eclipse maxima, using UBV photoelectricdata, parametric and nonparametric methods indicate significantcorrelations in at least one color between the size of the asymmetry, onthe one hand, and several additional parameters. These include: thecolor index of the asymmetry, the relative sizes of the hotter andsmaller components, and their distortion, the relative separation of thestars, and the logarithm of the period. The present study data arecharacterized by lower mean amplitudes and a much more even distributionof the asymmetry, with respect to sign, than that of O'Connell, andthere is a tendency for the brighter maximum to be redder, contrary toO'Connell's results. More than one mechanism for the O'Connell effect issuggested.
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The period distribution of unevolved close binary systems
Period distributions have been examined for various spectral types ofabout 600 (eclipsing and spectroscopic) close binaries, which are likelyto be substantially unevolved. The comparison with the previouscorresponding analyses of extensive (but heterogeneous) binary samplesallows a clarification of the extent of the evolutionary andobservational selection effects. Remarkably, this analysis reveals agreat deficiency of short period binaries (with periods corresponding tocase A mass transfer) in the whole spectral range. For the late spectraltypes, this result may be connected with postformation angular momentumloss caused by stellar wind magnetic braking; at least for the late Band A spectral range, a ready interpretation of this finding is thatclose binaries of corresponding periods and spectral types are rarelyformed.
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Statistics of categorized eclipsing binary systems Lightcurve shapes, periods, and spectral types
The statistics of the light curve morphologies, eclipse depths, orbitalperiods, and spectral types of about 1000 eclipsing binary systems areexamined, after attempting to subdivide these binaries into variousbasic evolutionary categories. The applicability of statisticalcriteria, based on light curve morphologies and eclipse depths, for thecategorization of eclipsing binaries has been found more limited thanpreviously believed. In particular, EW-type light curves turn out to begood indicators of contact systems (though not conversely), while EA-and EB-type light curves have little physical significance. Moreover,the study reveals a strong deficit of short-period noncontact systems inthe whole spectral range, together with an underabundance of early-typecontact binaries (compared with the number of late-type contact pairs).Interestingly, the distribution of evolved Algol-type systems isshifted, on average, to periods longer than those of unevolved detachedsystems in the OB and early A spectral range (and to shorter periods inthe F spectral range).
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Stellar activity in the short period subgroup of the RS CVn systems
The MgII 2800 A feature was studied in several spectrograms, obtainedwith IUE, for selected binaries among the RS CVn systems. The surfaceflux in emission was used as a measure of activity and its relevance isshown for the short period subgroup of the RS CVn like stars. Althoughthe sample size is low, indications of correlation between such activityand rotational velocity as well as the scale of irregular photometricdistortions are presented. All the systems show filling of the MgIIfeature between 2770 and 2818A with respect to the Sun. Results indicateactivity at least 10 times that of the Sun. This is attributed torotationally induced enhancement of emission.
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Observational results of the Berliner Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V. /BAV/
Results of observations of variable stars derived from 10,000 individualevaluations are presented for the years 1978 and 1979. Included are 172minima of 75 eclipsing binaries; 70 maxima of 17 RR Lyrae stars; 309results on 93 Mira stars; 90 results on 19 long-period, semi-regular,irregular and RV Tauri stars; and 6 results on 5 eruptive variablestars.
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Stellar masses
Problems of determining the masses of eclipsing and visual binary starsfrom the observational data are considered, and some of the availableresults are presented. Difficulties and uncertainties involved indetermining masses as well as absolute visual magnitudes or radii fromspectrographic observations obtained at 20 A/mm or higher dispersion andphotoelectric photometry are examined for the cases of detachedmain-sequence eclipsing binaries of types B6 to M, OB eclipsing systems,detached evolved eclipsing systems, resolved spectroscopic binaries,visual binaries and semidetached eclipsing systems. All available massesand radii known to any accuracy of 15% or better as well as colorindices and scale-dependent properties (effective temperature,bolometric luminosity, absolute visual magnitude) are tabulated for eachmember of the above classes of eclipsing binaries, and V magnitudes,color indices, masses, visual magnitudes and scale-dependent properties(effective temperature, bolometric luminosity, radius) are provided forthe 14 visual binary systems known with parallaxes greater than 0.9arcsec, at least three independent parallax determinations within 10% ofthe mean value, and orbits of quality 1 or 2. It is noted that improvedtechniques in observation and analysis are expected to lessen some ofthe difficulties pointed out.
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A catalogue of parameters for eclipsing binaries
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A catalogue of modern lightcurve synthesis photometric solutions of close binary systems
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Photoelectric Minima of Eclipsing Binaries
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Elements and intrinsic variability of VZ CVn
Three-color observations made from 1971 to 1976 revealed intrinsicvariability of the eclipsing binary star VZ CVn. From new times ofminimum the period is improved. Using only 1976 observations, two setsof elements, which can be considered as limits for the possible range ofvalues, have been deduced by applying the method of Wood (1972). Thesystem is detached, and the kind of variability is discussed.
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INHABITED SKY
