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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Aus der Sektion Bedeckungsveranderliche.
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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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149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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The Evolution of Cool Algols
We apply a model of dynamo-driven mass loss, magnetic braking, and tidalfriction to the evolution of stars with cool convective envelopes; inparticular, we apply it to binary stars where the combination ofmagnetic braking and tidal friction can cause angular momentum loss fromthe orbit. For the present we consider the simplification that only onecomponent of a binary is subject to these nonconservative effects, butwe emphasize the need in some circumstances to permit such effects inboth components.The model is applied to examples of (1) the Sun, (2) BYDra binaries, (3) Am binaries, (4) RS CVn binaries, (5) Algols, and (6)post-Algols. A number of problems regarding some of these systems appearto find a natural explanation in our model. There are indications fromother systems that some coefficients in our model may vary by a factorof 2 or so from system to system; this may be a result of the chaoticnature of dynamo activity.
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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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New labour on Algols: conservative or liberal?
I consider three topics related to the influence of magnetic braking,combined with tidal friction, on the orbital evolution of CVs. Firstly,I attempt to show that properties of Algols are roughly consistent withthe view that angular momentum loss (AML) takes place in systems withcool (G/K) components, but not in systems with hot (B/A) components.This is what one might expect if the AML requires an active dynamo asseen in the Sun and other cool stars. The timescale required is roughlyof the order of what might be expected by magnetic braking. Someenhanced mass loss (ML), presumably by stellar wind, also seems to benecessary in the more evolved Algol systems. Secondly, I urge thattheorists adopt a recipe for magnetic braking that is more on the linesof Stȩpień (1995) than of Skumanich (1972). Thirdly, Iargue that `interrupted magnetic braking', a mechanism often invoked toexplain the upper edge of the period gap in CVs, is not in accord withobserved properties of late M dwarfs and brown dwarfs, and that someother mechanism should be sought.
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The use of the NextGen model atmospheres for cool giants in a light curve synthesis code
We have written a light curve synthesis code that makes direct use ofmodel atmosphere specific intensities, in particular the NextGen modelatmosphere grid for cool giants (Teff<= 6800 K and log(g)<= 3.5, Hauschildt et al. \cite{hauschildt99}). We point out thatthese models (computed using spherical geometry) predict a limbdarkening behaviour that deviates significantly from a simple linear ortwo-parameter law (there is less intensity at the limb of the star). Thepresence of a significantly nonlinear limb darkening law has two mainconsequences. First, the ellipsoidal light curve computed for a tidallydistorted giant using the NextGen intensities is in general differentfrom the light curve computed using the same geometry but with the blackbody approximation and a one- or two-parameter limb darkening law. Inmost cases the light curves computed with the NextGen intensities havedeeper minima than their black body counterparts. Thus the light curvesolutions for binaries with a giant component obtained with models withnear linear limb darkening (either black body or plane-parallel modelatmosphere intensities) are biased. Observations over a wide wavelengthrange (i.e. both the optical and infrared) are particularly useful indiscriminating between models with nearly linear limb darkening and theNextGen models. Second, we show that rotational broadening kernels forRoche lobe filling (or nearly filling) giants can be significantlydifferent from analytic kernels due to a combination of the nonsphericalshape of the star and the radical departure from a simple limb darkeninglaw. As a result, geometrical information inferred from Vrotsin i measurements of cool giants in binary systems are likewise biased.
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Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
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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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Catalogue of stars in the northern Milky Way having H-alpha in emission
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The gas stream properties in the vicinity of the inner Lagrangian point in R CMa-type systems.
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UX Monocerotis: New Photometric and Spectroscopic Observations, Solutions, and Anomalies in an Active Mass-Transferring Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2385O&db_key=AST
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KU Cygni: New Spectroscopic and Photometric Solutions of a Long-Period Accretion-Disk Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.2378O&db_key=AST
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DN Orionis: A Long-Period Mass-Transferring "Slightly Detached" Algol Binary
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110.1809E&db_key=AST
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Rapid H-alpha emission variations in accretion disks in long-period ALGOLS
We demonstrate the continuous presence of large variations indouble-peaked H-alpha long period Algol-type binaries, using recentlyobtained CCD spectra. Most fluctuations occur on a time scale less thanor = an orbital period and a steady state in H-alpha emission ia neverreached. In AD Her (P = 10 d), H-alpha emission dropped in strength morethan a factor of five in one seven-day interval. Contemporay O I lambdaobservations showed no significant changes in oxygen absorption strengthor radial velocity during this time. We tentatively suggest that H-alphavariations arise from an inner-disk instability, possibly triggered bysmall modulations in the mass-transfer rate. This behavior isreminiscent of some cataclysmic variables.
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O I lamba 7774 absorption as a tracer of streams and disks in nondegenerate binary stars
We propose a new spectroscopic approach for observing circumstellarmatter in binary stars, based on the neutral oxygen lambda 7774absorption lines. We present oxygen equivalent widths and radialvelocities in 20 nondegenerate eclipsing binaries. We note limitationsand advantages of using this line to trace circumstellar matter inbinary systems, and confirm the presence of streams and rotatingaccretion disks in a number of short- long-period Algol systems. Wediscuss evidence for geometrically thick disks, and describe a smallradial infall superimposed on disk rotation in most long-period systems.We speculate that infall may be related to viscous dissipation in disks.We emphasize the great sensitivity of lambda 7774 in studying thekinematics of circumstellar matter in many nondegenerate binary stars.
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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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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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New rotational velocities for eclipsing binaries, and a comparison of spectroscopic and photometric rotations
Rotational velocities are determined spectroscopically for 38 eclipsingbinaries, including many long-period, nominally semidetached, systems.We note that spectroscopic rotations may differ from rotations derivedfrom light-curve modeling using the Wilson-Devinney program. In'direct-impact' mass-transferring systems, or in most systems withperiods smaller than about 7 days, observations suggest that the tworotations are usually about the same. In cases where the stream missesthe gainer and an accretion disk forms, however, photometric rotationestimates often exceed spectroscopic determinations. The possiblephysical significance of this situation is briefly discussed. Doubt iscast on the likelihood that the rotation of the hot component of U Sgehas changed detectably in the last 30 years.
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Radio observations of peculiar emission-line Algol binary stars
Twelve peculiar emission-line Algol (PELA) binaries were observed at cmwavelengths. Six of these objects, WW And (tentative), KX And, AM Aur,V644 Mon, DN Ori, and AY Per were detected at the 100 to 400 micro-Jylevel, corresponding to luminosity densities of order 10 exp 17erg/s/Hz. These luminosity densities, combined with nearly flat cmspectra and high brightness temperatures, are consistent with thenonthermal gyrosynchrotron radiation model proposed as the result ofobservations from the previous PELA survey. Also, the star V367 Cyg wasreobserved at thirteen different orbital phases; no variability wasfound within the errors. V367 Cyg's lack of variability andwell-determined average spectral index, however, imply the possibilityof a different emission mechanism, thermal bremsstrahlung, although thenonthermal model cannot be entirely ruled out. The characteristicbrightness temperature of thermal bremsstrahlung is only about 10,000 K,which means that the radius of the emission region would have to be muchlarger than previously assumed, about 10 AU. Suggestions for furtherobservations of all previously observed PELAS are presented in order todetermine the correct emission mechanism.
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Wind driven mass transfer in interacting binary systems
Quantitative estimates for conditions governing wind-driven masstransfer in interacting binary systems are presented. It is shown that,for a semidetached system in which the lobe-filling star is a red giant,mass loss from this star by the system as a whole can drive masstransfer. If the mass is lost on a sufficiently short time-scale, thiswind-driven mass transfer can dominate over the traditional-nucleardriven mass transfer. If additional angular momentum is lost because theescaping material is forced to corotate out to some Alfven radius, themass transfer can be driven at an even greater rate. In this case therates of mass transfer and of mass loss can be quantified as functionsof the mass ratio and the Alfven radius. Some numerical models of theexpected evolution are presented and observational predictions areexamined. It is found that the radii of evolved semidetached systems aremore consistent with wind-driven evolution than the traditionalnuclear-driven Riche-lobe overflow.
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Radio Emission From Peculiar Emission-Line Algol Binaries
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Investigation of statistical data for close binary stars.
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The Catalogue of Multiple and Double Stars of T-Associations in machine-readable form
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Eclipsing binaries, Lacerta to Orion, in 1969-1986
Photoelectric and visual observations of 37 known and suspectedeclipsing binaries are discussed. Revised light elements are derived forHP Lyr, V839 Oph and V530 Ori. WZ Leo is probably constant. Both of thealternative periods given in the literature for UW Ori appear to beincorrect. The period of V543 Ori is confirmed to be 52.42d., and not26.21d.
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A Study of the DM and SD Type Eclipsing Variables by Means of the Cluster Analysis Technique
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An Updated List of Eclipsing Binaries Showing Apsidal Motion
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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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INHABITED SKY
