Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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New Times of Minima of Some Eclipsing Binary Stars
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CCD Times of Minima of Selected Eclipsing Binaries
374 CCD minima observations of 187 eclipsing binaries are presented. Theobserved stars were chosen mainly from catalogue BRKA of observingprogramme of Variable Star Section of CAS.
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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.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Orbital Evolution of Algol Binaries with a Circumbinary Disk
It is generally thought that conservative mass transfer in Algolbinaries causes their orbits to be wider, so that the less massive staroverflows its Roche lobe. The observed decrease in the orbital periodsof some Algol binaries suggests orbital angular momentum loss during thebinary evolution, and the magnetic braking mechanism is often invoked toexplain the observed orbital shrinkage. Here we suggest an alternativeexplanation, in which a small fraction of the transferred mass forms acircumbinary disk, which extracts orbital angular momentum from thebinary through tidal torques. We also perform numerical calculations ofthe evolution of Algol binaries with typical initial masses and orbitalperiods. The results indicate that, for reasonable input parameters, thecircumbinary disk can significantly influence the orbital evolution, andcause the orbit to shrink on a sufficiently long timescale. Rapid masstransfer in Algol binaries with low mass ratios can also be accountedfor in this scenario.
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The Near-Contact Binary RU Ursae Minoris
The near-contact binary RU UMi with an F0-type primary and a K-typesecondary was observed in 2003. With the latest version of theWilson-Devinney code, the photometric elements were computed. Theresults reveal that RU UMi is a semi-detached system with the secondarycomponent filling its Roche lobe, which should lead to an increase ofthe period for conservative mass transfer between the two components.However, an orbital period analysis shows that the orbital period ofthis system undergoes a continuous decrease at a rate ofdP/dt=-1.72×10-8d yr-1. Therefore, thecontinuous period decrease may demonstrate that the system isnonconservative. This can result from a combined effect of mass transferfrom the secondary component to the primary one and mass and angularmomentum loss from the system. With the secular mass and angularmomentum losses, RU UMi may evolve from the present short-periodnear-contact system into an A-type contact binary.
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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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Bericht uber die 3. Veraenderlichen-Beobachtungswoche in Kirchheim.
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Bericht über die 2. Veraenderlichen-Beobachtungswoche an der VdS-Sternwarte Kirchheim 2005.
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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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CCD Observations of Times of Minima of Eclipsing Binaries
120 minima timings are reported for 39 E. B. systems observed from 2002to 2005 with the Rigel telescope at Winer Observatory. The timings weredetermined using a folded light curve analysis of light curves derivedfrom CCD images. Typical timing uncertainties were 30-60 sec.
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Sektion Bedeckungsveraenderliche: Lichtkurven in allen Phasen.
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Bericht uber die Veranderlichen-Beobachtungswoche an der VdS-Sternwarte in Kirchheim.
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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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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
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CCD Minima for Selected Eclipsing Binaries in 2003
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Search for A-F Spectral type pulsating components in Algol-type eclipsing binary systems
We present the results of a systematic search for pulsating componentsin Algol-type eclipsing binary systems. A total number of 14 eclipsingbinaries with A-F spectral type primary components were observed for 22nights. We confirmed small-amplitude oscillating features of a recentlydetected pulsator TW Dra, which has a pulsating period of 0.053 day anda semi-amplitude of about 5 mmag in B-passband. We discovered newpulsating components in two eclipsing binaries of RX Hya and AB Per. Theprimary component of RX Hya is pulsating with a dominant period of 0.052day and a semi-amplitude of about 7 mmag. AB Per has also a pulsatingcomponent with a period of 0.196 day and a semi-amplitude of about 10mmag in B-passband. We suggest that these two new pulsators are membersof the newly introduced group of mass-accreting pulsating stars insemi-detached Algol-type eclipsing binary systems.Table 4 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/405/231
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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.
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Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
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Orbital Period Studies of Two Algol-Type Eclipsing Binary Systems: TY Pegasi and X Trianguli
O-C curves of two EA-type eclipsing binaries, TY Peg and X Tri, areformed and studied in detail based on all available times of lightminimum. For TY Peg, it was discovered that the general trend of the O-Ccurve showed a downward parabolic variation, which indicates a secularperiod decrease with rate at dP/dt=-1.16×10-6 daysyr-1. When the secular decrease is removed from the O-Ccurve, the residuals can be described by several linear ephemerides,suggesting several sudden period jumps. For the other one, X Tri, it isfound that the general O-C trend also indicates a secular perioddecrease (dP/dt=-1.42×10-7 days yr-1), andseveral irregular period jumps are found to superpose on the long-timeperiod decrease. This kind of period change, irregular sudden jumpssuperposed on secular decrease, is typical for many other Algol-typebinary systems such as TU Her, UU And, Z Per, Y Psc, BO Mon, FH Ori, RTPer, and TX UMa. The period changes of these systems may be caused byorbital angular momentum loss via variable magnetic coupling and gravitycoupling between the components.
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HD 12582: A NEW delta Sct VARIABLE
We report the discovery of a new Sct variable
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The Origin of Cyclic Period Changes in Close Binaries: The Case of the Algol Binary WW Cygni
Year- to decade-long cyclic orbital period changes have been observed inseveral classes of close binary systems, including Algol, W UrsaeMajoris, and RS Canum Venaticorum systems and the cataclysmic variables.The origin of these changes is unknown, but mass loss, apsidal motion,magnetic activity, and the presence of a third body have all beenproposed. In this paper, we use new CCD observations and thecentury-long historical record of the times of primary eclipse for WWCygni to explore the cause of these period changes. WW Cyg is an Algolbinary whose orbital period undergoes a 56 yr cyclic variation with anamplitude of ~0.02 days. We consider and reject the hypotheses of masstransfer, mass loss, apsidal motion, and the gravitational influence ofan unseen companion as the cause for these changes. A model proposed byApplegate, which invokes changes in the gravitational quadrupole momentof the convective and rotating secondary star, is the most likelyexplanation of this star's orbital period changes. This finding is basedon an examination of WW Cyg's residual O-C curve and an analysis of theperiod changes seen in 66 other Algols. Variations in the gravitationalquadrupole moment are also considered to be the most likely explanationfor the cyclic period changes observed in several different types ofbinary systems.
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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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Survey of Hα Mass Transfer Structures in Classical Algol-Type Binaries
Five years of Hα survey data for 37 ``classical'' Algol-typebinaries are presented. All these systems have primaries with a spectraltype of A or B, have a period of less than 5 days, and are visible inthe Northern Hemisphere. Data were collected with the 1.02 m reflectorat the US Naval Observatory, Flagstaff Station. The survey consists ofover 460 system spectra. Each system was observed at least once duringthe 5 years, with many systems observed several times over severalepochs. Difference profiles are calculated for most spectra by modelingand subtracting the spectrum of the photospheres of the stellarcomponents. We examined each spectrum for the presence of mass transfer,stream-star and stream-disk interaction, a disk or circumstellar bulge,and chromospheric emission. We present information on the prevalence ofmass transfer activity, disk presence, and system states associated withparticular mass transfer structures. We show that no currently publishedstudy, including this one, has enough data for a rigorous statisticalidentification of system states.
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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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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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INHABITED SKY
