A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer
We present and analyse high-resolution optical spectra of two Algolbinaries, namely S Equ and KO Aql, obtained with the echellespectrograph at Catania Astrophysical Observatory. New accurate radialvelocities (RVs) for the hotter primary components are obtained. Thanksto the cross-correlation procedure, we were able to measure, for thefirst time to our knowledge, RVs also for the cool secondary componentsof S Equ and KO Aql. By combining the parameters obtained from thesolution of the RV curves with those obtained from the light-curveanalysis, reliable absolute parameters of the systems have been derived.The rotational velocity of the hotter components of S Equ and KO Aql hasbeen measured and it is found that the gainers of both systems rotateabout 30 per cent faster than synchronously. This is likely due to masstransfer across the Lagrangian L1 point from the cooler tothe hotter component. The lower luminosity of the mass-gainingcomponents of these systems compared to normal main-sequence stars ofthe same mass can also be an effect of the mass transfer. The Hαprofiles were analysed with the `synthesis and subtraction' techniqueand reveal clear evidence of mass transfer and accretion structures. Inboth systems, especially before the primary eclipses and afterwards, weclearly observed extra absorption lines. From the integrated absorptionand the RV variations of these features, we found that the massaccretion is very dense around the impact region of the hottercomponents. A double-peaked emission in the spectra of S Equ was seenoutside the eclipses. One of these peaks is likely originated in aregion between the centre of mass and the cooler component, which isoccupied by the flowing matter. Furthermore, the Hα differencespectra of S Equ and KO Aql also display emission features, which shouldbe arising from the magnetic activity of the cooler components.Based on observations collected at the Catania Astrophysical Observatory(Italy).E-mail: fsoydugan@comu.edu.tr
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Variable Stars in NSVS Database I. 86 New Variables in Andromeda
A search for light curves with variability in the NSVS data was carriedout in a 46 square-degree area in Andromeda. The field contains 51955light curves. We found 136 variables, 86 of them were not knownpreviously. Extrapolating the density of the variables in the field tothe whole NSVS, the total number of variables in the survey is estimatedto be 52000 - 61000.
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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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WW And: no decrease of amplitude
I compare reported visual observations of the eclipsing binary WWAndromedae of the 1920ies with professional photometries of 1991 andwith my own visual data. Contrary to some presumptions in theprofessional literature, the amplitude of light variation since itsdiscovery probably never changed and always was as bad as 0,6mag. WW Andtherefore is no rewarding object of visual observation.
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SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
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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 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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Is asynchronism in semidetached binary systems real?
We analyze statistical relationships between the parameters ofAlgol-type binaries with asynchronous rotation of the primary componentsand provide observational evidence for denser, more extended gaseousenvelopes in the eclipsing systems of this group. We conclude thatasynchronism of the primary components in such systems is not real. Thelines that are used to determine the rotational velocities of thesecomponents originate mostly in the part of the atmosphere which acquiresan additional angular momentum during the interaction with the gasstream and produces a transient accretion disk near the equatorialplane.
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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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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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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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WW Andromedae - Photometric and spectroscopic solutions for a peculiar eclipsing binary
We present and analyze intermediate-band uvbyI (Kron) photometry and CCDspectroscopy of the poorly known long-period system WW And. Early visualphotometry suggested a totally eclipsing geometry, while our new dataclearly show shallower partial eclipses. Double-peaked H-alpha emissionis prominent at all orbital phases and times, indicating the presence ofa permanent accretion disk around the hotter mass-gaining star.Photometric and radial-velocity solutions with the new Wilson code yieldestimates of absolute system parameters. These simultaneous multicolorphotometric solutions suggest that the cool star does not quite fill itsRoche lobe, and that mass transfer in this binary probably occurs bysome mechanism other than lobe overflow. WW And may share with RW Per ahistorical trend of gradually decreasing primary eclipse depth.
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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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Radio Emission From Peculiar Emission-Line Algol Binaries
Not Available
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Investigation of statistical data for close binary stars.
Not Available
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Eclipsing Binaries - Andromeda to Camelopardalis in 1972-1983
Not Available
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A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
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The q-log P distribution of classical ALGOLS
Data on a large sample (approximately 400) of candidates for theclassical Algol-type eclipsing binary configurations have beencollected. The mass-ratio q has been calculated on the assumption oftheir semi-detached nature, and then compared with corresponding periodfor some subsets of the sample. The tendency to slight overluminosity(compared with corresponding MS stars) of the primaries in classicalAlgols is confirmed. The role of the loss of angular momentum inclassical Algol evolution is considered, together with a method fordetermining representative parameters to characterize such effects usingthe sample data. The possible existence of a class of post-contactclassical Algols is noted.
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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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A catalogue of parameters for eclipsing binaries
Not Available
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Seventh catalogue of the orbital elements of spectroscopic binary systems.
Not Available
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Spectroscopic binaries with circular orbits.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..544L&db_key=AST
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Photographic observations of six variables in Andromeda.
Not Available
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Osservazioni di stelle variabili nei campi attorno a Omicron Persei e K Andromedae
Not Available
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Minima and periods of eclipsing stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1957AJ.....62..371W
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Uber die Massen von Bedeckungsveranderlichen mit bekannter Radialgeschwindigkeit nur des Hauptsterns.
Not Available
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INHABITED SKY
