BL Andromedae and GW Tauri: close binary stars in a key evolutionary stage
A photoelectric light curve of BL And is presented along with the firstCCD light curve of GW Tau. Both objects are short-period eclipsingbinaries and were observed in 2003 or 2004. Photometric elements werecomputed using the latest version of the Wilson-Van Hamme code. Theresults reveal that BL And is a semidetached system with the primarycomponent filling its Roche lobe and the secondary one almost fillingbut still detached, while GW Tau is a marginal-contact binary systemwith a small degree of contact (f= 10.9 per cent) and a largetemperature difference of about 3100K. All available eclipse times,including new ones, were analysed for each system. It was found that theorbital period of BL And is decreasing at the rate of dP/dt=-2.36× 10-8 (+/-0.09)dyr-1 while that of GW Taumay be decreasing or oscillating. We think period decrease is moreprobable. The derived configuration and secular period decrease for BLAnd combined with the asymmetry of the light curve indicate that thissystem may evolve from the present semidetached phase into a contactstage, with mass transfer from the primary component to the secondaryone through the L1 point, or that it might just undergo thebroken stage predicted by the theory of thermal relaxation oscillations.In contrast, GW Tau is a marginal-contact binary in poor thermal contactand may be at the beginning of the contact phase.
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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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Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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CCD Times of Minima of Selected Eclipsing Binaries
682 CCD minima observations of 259 eclipsing binaries made mainly byauthor are presented. The observed stars were chosen mainly fromcatalogue BRKA of observing programme of BRNO-Variable Star Section ofCAS.
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
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Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
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29 frequencies for the δ Scuti variable BI CMi: the 1997-2000 multisite campaigns
A multisite campaign of BI CMi was carried out with excellent frequencyresolution and high photometric accuracy from 1997 to 2000, includingtwo long observing seasons. 29 pulsation frequencies could be extractedfrom the 1024h (177 nights) of photometry used. The detected frequenciesinclude 20 pulsation modes in the main pulsation frequency range from4.8 to 13.0cycled-1 (55 to 150μHz), eight linearcombinations of these frequencies, and a very low frequency at1.66cycled-1. Since the value of the low frequency at1.66cycled-1 cannot be identified with a linear combinationof other frequencies, g-mode pulsation is suspected, but rotationalmodulation of abundance spots cannot be ruled out. BI CMi, which issituated near the cool edge of the classical instability strip, may beboth a δ Scuti and a γ Doradus star. Another outstandingproperty of BI CMi is the presence of a number of close frequency pairsin the power spectrum with separations as small as0.01cycled-1. A rotational velocity ofvsini=76+/-1kms-1 was determined from a high-dispersionspectrum. From phase differences, the dominant modes can be identifiedwith l values from 0 to 2. The spectral type and evolutionary status ofBI CMi are examined.
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149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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Das Brunner Punktesystem.
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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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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A rediscussion on the eclipsing binary YY Canis Minoris
We have reanalysed the UBV light curves of \cite[Abhyankar(1962b)]{abh62b} using the 1993 version of Wilson-Devinney computerprogramme with a view to derive a consistent solution in all the threepassbands and to answer the discordant opinions on the general pictureof YY CMi. Initially, a preliminary unspotted solution was obtained anda photometric mass ratio was derived. From the present analysis, weobtained a mass ratio of q=0.89 which differs from the mass ratio of 0.8derived by \cite[Giuricin & Mardirossian (1981)]{giu81} and 0.65derived by \cite[Abhyankar (1962b)]{abh62b} but agrees with the value of0.885 derived by \cite[Niarchos et al. (1998)]{nia98}. Finally, thelight curves were modelled by introducing a spot on the cooler secondarycomponent to represent the observed light curve asymmetries. Assumingthe mass of the primary component to be 1.56 msun(F1V), theabsolute elements of YY CMi are found to be mc=1.39msun, Rh=2.52 Rsun, Rc=2.38Rsun, Log Lh=1.13 Lsun, LogLc=0.86 Lsun, Log gh=3.83 and Loggc=3.83. The primary and secondary components are found to beslightly overluminous and bigger in size when compared to stars of thesame mass. In the H-R diagram (log Te versus log L, ZAMS),both the components are above but near the ZAMS suggesting that both ofthem have left the main sequence and have come into contact. Our resultsessentially agree with those of \cite[Niarchos et al. (1998)]{nia98}based on V passband only.
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Photoelectric Minima of Selected Eclipsing Binaries
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YY Canis Minoris: Contact or near contact system?
New V photoelectric observations of the eclipsing system YY CMi,obtained at La Silla, Chile, and Merate Observatory, Italy, arepresented. New times of minima and ephemeris based on our observationsare also given. The V light curve was analysed by using the WD code toderive the geometrical and physical parameters of the system. Since nospectroscopic mass ratio is available, the q-search method was appliedto yield the preliminary range of the mass ratio in order to search forthe final solution. First the unspotted solution was carried out byusing the unperturbed parts of the light curve and applying the DCprogram of the WD code. The solution was performed by assuming contact(mode 3) and semi-detached (mode 4) configuration, since noclassification of the system is possible from the shape of the lightcurve. The solution in mode 4 does not lead to an acceptable model,since the secondary was found to be slightly overcontact. Therefore thecontact solution was finally adopted. Moreover the light curvepeculiarities (Max II fainter than Max I and excess of light around thephase 0.32) were explained by assuming a cool and a hot spot on thesurface of the secondary (cooler) component. The degree of contact isvery small (f~ 3%) and the thermal contact is poor (T_1-T_2)~ 650 K.These results together with the high photometric mass ratio q~ 0.89indicate that YY CMi is very probably a system at the beginning or theend of the contact phase. Based on observations partly made at theEuropean Southern Observatory (ESO). Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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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 Eclipsing Binaries
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Measurement and analysis of rotation in close binaries. II. Calculation of synchronism.
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Measurement and Analysis of Rotation in Close Binary Stars - Part One - Observations and Results
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Searching for Intrinsic Variations in Eclipsing Binary Stars
Using a database of nearly 4000 visual estimates made by the authorbetween 1967 and 1993, evidence for intrinsic variations on a time scaleof years is sought after 64 eclipsing binary stars. While none is foundfor most stars, certainb objects warrant further investigation.
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New Photoelectric Minima of Some Eclipsing Binaries
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The early spectral type contact binary systems.
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Eclipsing Binaries - Cancer to Corona Borealis in 1972-1984
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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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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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Yy-Canis - an Evolved Contact Binary System
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&A....94..391G&db_key=AST
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Errata Notices in the Kennedy 1976 MK Tape
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A catalogue of parameters for eclipsing binaries
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Results of BAV observations of variable stars
In this 12th compilation of BAV, results of observations are given fromthe years 1976 and 1977 for 231 observed minima of 58 eclipsingbinaries, 108 maxima of 25 RR Lyrae stars, four maxima of four DeltaCephei stars, and four maxima of one Delta Scuti star.One-hundred-eighty-two results of 23 long-period, semiregular, irregularand RV Tauri stars are also given.
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