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Photoelectric Times of Minima of Some Eclipsing Binaries
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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.
| Minima Kurt Locher 2004-2005
Minima observed 2004..2005 by Kurt Locher visually, not accepted by IBVSas part of BBSAG Bulletin.
| 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.
| Astrometric orbits of SB^9 stars
Hipparcos Intermediate Astrometric Data (IAD) have been used to deriveastrometric orbital elements for spectroscopic binaries from the newlyreleased Ninth Catalogue of Spectroscopic Binary Orbits(SB^9). This endeavour is justified by the fact that (i) theastrometric orbital motion is often difficult to detect without theprior knowledge of the spectroscopic orbital elements, and (ii) suchknowledge was not available at the time of the construction of theHipparcos Catalogue for the spectroscopic binaries which were recentlyadded to the SB^9 catalogue. Among the 1374 binaries fromSB^9 which have an HIP entry (excluding binaries with visualcompanions, or DMSA/C in the Double and Multiple Stars Annex), 282 havedetectable orbital astrometric motion (at the 5% significance level).Among those, only 70 have astrometric orbital elements that are reliablydetermined (according to specific statistical tests), and for the firsttime for 20 systems. This represents a 8.5% increase of the number ofastrometric systems with known orbital elements (The Double and MultipleSystems Annex contains 235 of those DMSA/O systems). The detection ofthe astrometric orbital motion when the Hipparcos IAD are supplementedby the spectroscopic orbital elements is close to 100% for binaries withonly one visible component, provided that the period is in the 50-1000 drange and the parallax is >5 mas. This result is an interestingtestbed to guide the choice of algorithms and statistical tests to beused in the search for astrometric binaries during the forthcoming ESAGaia mission. Finally, orbital inclinations provided by the presentanalysis have been used to derive several astrophysical quantities. Forinstance, 29 among the 70 systems with reliable astrometric orbitalelements involve main sequence stars for which the companion mass couldbe derived. Some interesting conclusions may be drawn from this new setof stellar masses, like the enigmatic nature of the companion to theHyades F dwarf HIP 20935. This system has a mass ratio of 0.98 but thecompanion remains elusive.
| 163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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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
| 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.
| 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.
| 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.
| 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.
| Apsidal Motion in Double Stars. I. Catalog
A catalog of 128 double stars with measured periods of apsidal motion iscompiled. Besides the apsidal periods, the orbital elements of binariesand physical parameters of components (masses, radii, effectivetemperatures, surface gravities) are given. The agreement of the apsidalperiods found by various authors is discussed.
| Observations of radio stars at the Valinhos CCD Meridian Circle
We present the astrometric results from the optical observation of 16stars from the list of \cite[Wendker (1995)]{wend95}, with detected orsuspected radio emission. The results are given on the Hipparcos/Tychoreference frame. The stars are evenly distributed in right ascension andthe declinations range from -15.6(deg) to +28.6(deg) . Thisdistribution, also allowed to obtain positions relative to the TwinAstrographic Catalogue (TAC 1.0). The observations were carried out withthe Valinhos CCD Meridian Circle, in Brazil, operating in drift scanningmode. The average positional precision is at 40 mas and generally below2 mas/yr for proper motions, obtained with the new reductions of theAstrographic Catalogue - AC2000, as first epoch. In the strips takenfrom the observation of the 16 radio stars, 573 Tycho stars, 545 ACTstars and 566 TAC stars were found. The analysis of the independentreductions made relatively to those frames and the large number ofcommon stars enables to focus on the equatorial zone, as represented bythe three catalogues. As a result, the quality of Valinhos observationswith regard to ACT and TAC internal accuracies is verified. Table 1 ofthis paper, plus 16 additional tables with observed positions for theACT reference stars, are available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Orbital period modulation and quadrupole moment changes in magnetically active close binaries
We discuss the main characteristics of the orbital period modulation inclose binaries with late-type components. We focus on the variousphysical scenarios proposed to explain this phenomenon and, inparticular, Hall's (1989) suggestion that it may be connected withmagnetic activity. Starting from the work of Applegate (1992) and Lanzaet al. (1998a), we develop an integral approach to evaluate thegravitational quadrupole moment of an active star and its variations,which we consider to be an important driver of the observed orbitalperiod changes. The method applies the tensor virial theorem afterChandrasekhar (1961) and directly relates the variation of thequadrupole moment with the changes of kinetic and magnetic energy of thestellar hydromagnetic dynamo. Particular effort has been applied inminimizing the number of free parameters entering the problem. A sampleof 46 close binaries with period changes of alternate signs has beenstudied by our method. The amplitude of the quadrupole moment changeappears to decrease with increasing angular velocity, implying that thetime-variable part of the kinetic energy of rotation varies as delta{cal T}/{cal T} ~ Omega ({-0.93+/-) 0.10}, with a correlationcoefficient of 0.83. The length of the cycle of the orbital periodmodulation seems to be correlated with the angular velocity asPmod ~ Omega ({-0.36+/-) 0.10}, but with a smallercorrelation coefficient of 0.62. These results support the suggestionthat a distributed non-linear dynamo is at work in the convectiveenvelopes of very active stars and that it strongly affects thedifferential rotation. We also discuss the energy budget of the processresponsible for the quadrupole moment variation and find that, onaverage, only ~ 10% of the energy required to maintain the differentialrotation may be lost by dissipation in the turbulent convective envelopeduring a cycle of the orbital period change. The problems of themagnetic field geometry and stability and the relationship between thelength of the activity cycle, as determined by the change of the area ofthe starspots and the orbital period modulation, respectively, are alsoaddressed.
| Interaction of Eclipsing Binaries with their Environment
The interaction of eclipsing binary star systems with the mass around(in the form of star, planet, envelope or disk) affects the orbitalperiod of these systems. Thus, the long-term orbital period changes ofeclipsing binaries which can be deduced by using the observed times ofeclipse minima provide a good tool in understanding the interaction ofeclipsing binaries with their environment. In the present contributionmany examples of the orbital period changes of different eclipsingbinaries are presented and interpreted in terms of the interaction withtheir environment.
| On the invisible components of some eclipsing binaries.
The aim of this paper is to search for evidences for the presence ofunseen companions in some eclipsing binary systems using their O-Cdiagrams. A total of 8507 times of minima (6890 visual and 1617photographic or photoelectric ones) of 18 systems have been collectedfrom the remarkable database of late Dieter Lichtenknecker(Lichtenknecker 1988) and from other more recent papers. Assuming thatlight-time effect (LITE) is responsible for the periodic components onthe O-C diagrams sets of orbital parameters were derived using Kopal's(1978, Dynamics of close binary systems. D. Reidel. Co.) method. In somecases (AB And, TV Cas, XX Cep, AK Her) the resulting orbital parametersand masses of the hypothetical third components are physicallyacceptable. Other systems show good evidence for multiplicity, but theavailable data sets are not suited to compute reliable solutions (W Del,U Peg, AT Peg, ST Per). For RT And, XZ And, OO Aql, Y Cam, RS CVn, CQCep, U CrB and MR Cyg) an unambigous identification of third componentsis not possible. In the cases of TW Cas and SW Lac we could not find anyLITE solution at all.
| A search for possible unresolved components in eighteen eclipsing binaries.
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| Color Change Caused by Microlensing of Binary and Multiple Stars
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| Effects of Gravitational Microlensing of Binary and Multiple 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.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Quantitative spectral types for 19 Algol secondaries
Time-resolved spectra of 19 short-period Algol-type binary star systemsobtained during total eclipse are used to derive the temperaturespectral class of the mass-losing secondary component. The spectralclassifications employed a quantitative comparison of the strengths ofabsorption features in stars of known spectral class with those of theprogram stars. The luminosity spectral class can not be determined fromthese data, so both main-sequence and giant stars were used for thecomparison. Our spectral types are compared with published types andfound to be generally in good agreement, unless the published types arederived from the light curves. The photometrically determined types aresystematically later than our directly determined types. This effect isshown also to exist in catalogs of Algol parameters.
| Remarks on the Apsidal Motion of TX Ursae Majoris
The hypothesis of apsidal motion is reviewed and it is found that onlysuch a phenomenon cannot explain the observed O - C diagram, for binarysystem TX Ursae Majoris.
| 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.
| W Delphini - Request for New Observations
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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.
| Rotation statistics of Algol-type binaries and results on RY Geminorum, RW Monocerotis, and RW Tauri
Rotation rates and other parameters are estimated from light curves ofthree Algol-type binaries, and rotation statistics based on bothspectral line broadening and light curves are collected for 36 Algolsystems. The statistics suggest that a subset of Algols have primarystars which rotate at the centrifugal limit and that many Algols havesufficient continual mass transfer to maintain nonsynchronous rotation.A formal procedure for estimating the critical rotation rate(centrifugal limit) is described. It is found that RY Gem rotates about14 times faster than synchronously, but not close to its centrifugallimit of about 24 times. For RW Mon, the rotation is about five timessynchronous. For RW Tau it was not possible to estimate the rotationfrom the light curves, but consistency with a published result from linebroadening is found.
| Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
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