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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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/.
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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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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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A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
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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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Magnetic activity and evolution of Algol-type stars - II
We examine the possibility of probing dynamo action in mass-losingstars, components of Algol-type binaries. Our analysis is based on thecalculation of non-conservative evolution of these systems. We model thesystems USge and betaPer where the more massive companion fills itsRoche lobe at the main sequence (case AB) and where it has a smallhelium core (early case B) respectively. We show that to maintainevolution of these systems at the late stages which are presumablydriven by stellar `magnetic braking', an efficient mechanism forproducing large-scale surface magnetic fields in the donor star isneeded. We discuss the relevance of dynamo operation in the donor starto the accelerated mass transfer during the late stages of evolution ofAlgol-type binaries. We suggest that the observed X-ray activity inAlgol-type systems may be a good indicator of their evolutionary statusand internal structure of the mass-losing stellar components.
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Radio emission from Algol-type binaries. I. Results of 1992-1993 VLA survey
In this paper we report on a 5 GHz survey of 26 Algol-type binaries. Sixsystems were detected. We combine the new results with previouslypublished data to derive some radio characteristics of Algols and tocompare them with those of other active binaries. The radio detectionrate of 30 %, a factor that is somewhat smaller compared to the case ofRSCVn-type, does not seem to be due to a reduced coronal activity. Infact, Algols share many similarities with the radio behavior of RS CVnsand the 5 GHz luminosity functions of both kind of systems look quitesimilar. Among the different possibilities, the high radio variabilityand distances, which, on average, are larger than those of RS CVns, seemto be the most reasonable explanation for the apparently reducedactivity at radio wavelengths.
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Magnetic activity and evolution of Algol-type stars
We examine the possibility of tracing dynamo action in mass-losing starsthat are components of Algol-type binaries. Our analysis is based on thecalculation of the non-conservative evolution of a system that initiallyconsists of a 1.65-Msolar star with a small helium core and a0.99-Msolar main-sequence companion. We perform our calculations for theevolutionary model of S Cnc in which a more massive companion fills itsRoche lobe at the orbital period of the system P_orb~1.12d. We show thatto maintain the late stages of evolution of this system, which aredriven by stellar `magnetic braking', an efficient mechanism thatproduces large-scale surface magnetic fields in a donor star is needed.We discuss the relevance of dynamo action in a donor star to the stagesof accelerated mass transfer in the evolution of Algol-type systems.
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The gas stream properties in the vicinity of the inner Lagrangian point in R CMa-type systems.
Not Available
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Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
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On X-ray interacting binaries with no compact components.
Our present knowledge of the interacting binary β Persei (Algol) onthe basis of published X-ray and EUV observations is summarized and somegeneral comments on future work are made.
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On Accretion Component of the Flare Activity in Algol
A critical assessment of the observational data on flare activity inAlgol-type binaries is given. Two sites of the flare activity have beenidentified in Algol through observations in the X-ray and microwaveregions. One of them is apparently the accretion shock region on theB8-type primary component. Another, the predominant one, is associatedwith coronal mass ejection from the Roche lobe filling late-typesecondary. We still do not know the morphology of the circumbinary gaswith sufficient precision to determine the relative contribution fromboth these sources of activity. Future observations should concentrateboth on systems like U Cep with mass-loss dot M =~ 10(-6}M_{sun) /y andon Z Vul-type objects where secondaries are earlier than F2-type stars,i.e. presumably without an extensive convection zone. A simple model ofradially expanding stellar wind in a binary system is presented. Theeffect of anisotropy which appears due to displacement of a sonic point,caused by the gravitational field of the companion star, isinvestigated. We estimate the X-ray flux for Algol, caused by theaccretion to the primary component and find satisfactory agreement withthe X-ray Ginga data for a mass transfer rate dot M =(0.4-2.0) *10(-11}M_{sun) /y.
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Evidence of magnetic activity in short-period Algol binaries
The cool G- to K-type secondaries in short-period Algol-type binariesare expected to be magnetically active like the RS CVn binaries becauseof their rapid rotation and outer convective layers. There is nowgrowing evidence of such activity, primarily from radio and X-rayobservations, but there is still little or no information about most ofthe other indicators of magnetic activity. In this work, we havecollected the evidence for magnetic activity in a selected group of 15short-period Algols and have examined the possibility that part of theH-alpha emission detected in these systems may indeed arise from thechromosphere of the cool star and not exclusively from circumstellarmaterial.
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Close binaries observed polarimetrically
Not Available
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Photometric analysis of the semidetached binary system S Velorum.
New absolute parameters of S Vel have been derived from a reanalysis ofphotometric data taken from Sisteró (1971).
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The visual surface brightness method and the radii of dwarf Cepheids
In order to determine the radii of dwarf Cepheids by applying the visualsurface brightness method, the empirical relationship between F(v) and(b - y) was derived. Seventeen stars of spectral type A to F, where bothangular diameters and uvby beta photometric data are available, wereselected from the literature. A theoretical F(v), (b-y) relation wasderived by using the Kurucz model atmospheres. It was found that thetheoretical relation is strongly dependent upon metallicity and surfacegravity. To demonstrate that the visual surface brightness method is aneffective way to determine the radii of dwarf Cepheids, both theoreticaland empirical relations were applied to seven dwarf Cepheids. The mostreliable result was obtained for AD CMi where the quality of the radialvelocity data is superior.
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Statistical study of semi-detached and near-contact semi-detached binaries
A statistical study was made of 107 semidetached with combined lightcurve solutions. An empirical period-dependent mass-radius relation wasderived, thereby revealing the impossibility of having evolvedsemidetached systems with very short periods. Statistically, thenear-contact semidetached systems have the common properties of nearlyequal mass densities of the components, larger mass-ratios, shorterperiods and smaller specific angular momenta, and their A- F-typesecondaries generally have greater densities than the secondaries ofclassical Algol systems of the same spectral types. A detaileddiscussion is also made in this paper on the evolution of near-contactsemidetached binaries.
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Investigation of statistical data for close binary stars.
Not Available
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Program of Parallax Measurements from Space for the Nearest Eclipsing Binaries
Not Available
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A Study of the DM and SD Type Eclipsing Variables by Means of the Cluster Analysis Technique
Not Available
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Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
Not Available
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Superionized plasmas in Algol binaries
Outflowing gas is studied for semidetached binaries of the Algol type. Asurvey of 11 systems observed during the total primary eclipse showsthat the same type of emission-line spectrum appears, but that importantdifferences exist, correlated with the character of the mass-accretingstar, although it is not clear if the correlation is with spectral typeor with mass. The line emitting plasma is specified, but the dominantelectron temperature varies from system to system and determines therelative line strengths. Evidence for CNO processing, affecting theabundance ratios C/N, is also present.
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A microwave survey of southern active stars
The results of a survey of 153 active-chromosphere stars made with theParkes 64-m telescope at 5.0/8.4 GHz from 1981 to 1987 are reported.Microwave emission was detected from 70 stars on at least one occasion,with the highest detection rate of 68 percent from the RS CVn group. TheCa II stars and Algol-type binaries yielded detection rates of 44 and 30percent, respectively. The maximum powers emitted by the stars at5.0/8.4 GHz ranged over five orders of magnitude, with a median of 2.5 x10 to the 10th W/Hz. The maximum brightness temperatures had a smallerrange of three orders of magnitude, with a median of 3.6 x 10 to the 9thK.
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Semidetached systems - Evolutionary viewpoints and observational constraints
The present knowledge on the evolution of semidetached systems isreviewed. Characteristics of observed systems are discussed and generalproperties tested by the behavior of theoretical models. New models ofmass accreting companion stars are computed. The accretion phase isdivided into a fast and slow phase with an accretion rate depending onthe initial mass of the mass losing star and on the initial mass ratio,asssuming the systems are undergoing a case B of mass transfer. Theresults are compared with observed systems with masses of the gainerslocated within the theoretical range. Up to now no computations existfor the evolution of medium mass close binaries including overshootingof the convective core. However some of the influences of extendedconvective mixing on the interaction of close binaries are investigated.A larger probability for the occurrence of case A of mass exchange and alarger remnant mass at the end of the process are the most importantresults. Finally the investigation into the origin of individual systems(in mass, mass ratio and period) is discussed, showing that progressboth in observations and in theoretical models result in a more detailedand more restricted determination of the initial parameters of theindividual systems.
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Optical and infrared photometry of southern early-type shell stars and pre-main-sequence variables
A catalogue of optical and infrared photometry is presented covering theepoch 1980 to 1984 for a sample of 53 pre-main-sequence stars and otheremission-line objects, mainly of early spectral type. The JHKL data aregenerally simultaneous with optical photometry in either the UBVRI orStromgren uvby systems, and the H beta index is used as a photometricmonitor of spectrum variability. This catalogue will form a valuabledata set for future studies of the nature and origin of variability inthis class of object.
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Circumstellar material in ALGOLS and Serpentids
The observations of the emission lines of C 4, N 5, Si 4, etc. ininteracting binaries of the Algol and W Serpentid types are reviewed. Sofar, seven Serpentid are known, and seven bona fide Algol-typesemidetached systems were found to display the same kind of emissionlines, only on a weaker scale. Interesting differences are observed inboth the absolute and relative strengths of the emission lines. In somesystems, the C 4 resonance doublet is the strongest, while in others,the N 5 doublet is definitely stronger. The main cause of this dichotomyis suspected to be the varying degree of CNO processing of the observedmaterial. But the variable ratio of the strength of the C 2 line to thatof the C 4 line suggests temperature differences between the emittingregions of the individual systems, too.
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A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
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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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INHABITED SKY
