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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.
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
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| Doppler tomography of Algols
The technique of Doppler tomography has been influential in the study ofmass transfer in Algol-type interacting binaries. The Algols contain ahot blue dwarf star with a magnetically-active late-type companion. Inthe close Algols, the gas stream flows directly into the photosphere ofthe blue mass-gaining star because it does not have enough room to avoidimpact with that star. Doppler tomograms of the Algols have beenproduced from over 2500 time-resolved spectra at wavelengthscorresponding to Hα, Hβ, He I (6678 Å), Si II (6371Å) and Si IV (1394 Å). These tomograms display images ofaccretion structures that include a gas stream, accretion annulus,accretion disk, stream-star impact region, and occasionally a source ofchromospheric emission associated with the cool, mass-losing companion.Some Algol systems alternate between stream-like and disk-like states,and provide direct evidence of active mass transfer within the Algols.This work produced the very first images of the gas stream for theentire class of interacting binaries, and demonstrated that the Algolsare far more active than formerly believed, with variability on timescales of weeks to months.
| 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
| A period investigation of two chromospherically active binary stars: RT Coronae Borealis and PW Herculis
Orbital period variations of two chromospherically active binarysystems, RT CrBand PW Her, arepresented. It is shown that the orbital period of RT CrB undergoes acyclic oscillation with a period of 53.9years. For PW Her, an alternatechange, with a period of 42.7years, is found to superimpose on a rapidsecular increase (dP/dt=+3.53×10-6 days/year). If theperiod oscillations of those two systems are caused by the light-timeeffect of a third body, the analysis for RT CrB indicatesthat the third body would be a low-mass main-sequence star, while, forPW Her, the massof the third body should be no less than 7.8 Msolar. Since nospectral lines of the third body were seen in PW Her from thespectroscopic study by Popper [AJ 100 (1990) 247], if there is a thirdbody in the system, it can only be a black hole. However, as bothcomponents in the two binary stars were showing strong chromosphericactivity, the alternate period variations are more plausibly explainedas the result of magnetic activity cycles. No secular period changes ofRT CrB are found,which is in agreement with the detached evolved configuration of thesystem. The long-term period increase of PW Her may indicatethat it is on an active phase of mass transfer(dm/dt=2.17×10-6 Msolar/year).
| Orbital Period Changes of Algol-type Binaries: S Equulei and AB Cassiopeiae
The orbital periods of two Algol-type binaries, S Equ and AB Cas, arestudied based on all available times of minima. It is found that the O-Cvariations of both systems can be represented by a parabolic and aperiodic term. S Equ has an accretion region due to mass transfer asshown by Richards and coworkers and Richards & Albright. On theother hand, Zola obtained a light-curve solution with a third light. Ourstudy reveals evidence of mass transfer and third component stars inboth systems. The parabolic terms in the O-C variations are due to masstransfer from less massive to more massive components, which isconsistent with the semidetached nature of both systems. The periodicterms are explained with the additional third stars in the systems. Itis interesting that there is no sign of a magnetic braking effect fromthe cool secondary in the O-C variation of either system.
| 149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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| Das Brunner Punktesystem.
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| S Equulei: A Low Mass Ratio Algol-Type Eclipsing Binary at the Active Phase of Mass Transfer
Orbital period change of a low mass ratio (q=0.13) Algol-type eclipsingbinary, S Equulei, is presented based on the analysis of itscentury-long times of light minimum. Alternate period changes arediscovered to superimpose on a rather rapid period increase with rate ofdP/dt=+1.27×10-6 days yr-1. The alternateperiod changes can be explained either by the variation in thegravitational quadruple momentum via the cyclic magnetic activity of theG-type secondary or by the light-time effect via the presence of a thirdbody. Since the third-body assumption is in good agreement with Zola'sphotometric solution, S Equ may be a truly triple system. The third bodyis rotating in an eccentric orbit (e'=0.37) with an orbitalinclination of i'=16deg, which is rather smallerthan that of the eclipsing binary system (i=88.3d). This indicates thatthe third body may be captured by the eclipsing pair. New accuratephotometric and spectroscopic data over the next decade are veryimportant to verify this conclusion. The rapid period increase suggeststhat S Equ is a low mass ratio Algol-type binary system in an activephase of mass exchange. To satisfy such a period increase, aconservative mass transfer from the less massive to the more massivecomponents would be of the order dm/dt=4.94×10-8Msolar yr-1.
| Photometric Solutions for Semidetached Eclipsing Binaries: Selection of Distance Indicators in the Small Magellanic Cloud
Estimation of distances to nearby galaxies by the use of eclipsingbinaries as standard candles has recently become feasible because of newlarge-scale instruments and the discovery of thousands of eclipsingbinaries as spin-off from Galactic microlensing surveys. Publishedmeasurements of distances to detached eclipsing binaries in the LargeMagellanic Cloud combine stellar surface areas (in absolute units)determined from photometric light and radial velocity curves withsurface brightnesses from model atmospheres and observed spectra. Themethod does not require the stars to be normal or undistorted and is notlimited in its applicability to the well-detached systems that havetraditionally been considered. We discuss the potential usefulness ofsemidetached vis à vis detached eclipsing binaries for distancedetermination and examine and quantify criteria for their selection fromlarge catalogs. Following our earlier paper on detached binaries in theSmall Magellanic Cloud (SMC), we carry out semidetached light-curvesolutions for SMC binaries discovered by the OGLE collaboration,identify candidates for SMC distance estimation that can be targets offuture high-quality observations, and tabulate results of OGLElight-curve solutions. We point out that semidetached binaries haveimportant advantages over well-detached systems as standard candles,although this idea runs counter to the usual view that the latter areoptimal distance indicators. Potential advantages are that (1)light-curve solutions can be strengthened by exploiting lobe-fillingconfigurations, (2) only single-lined spectra may be needed for radialvelocities because the mass ratio can be determined from photometry inthe case of complete eclipses, and (3) nearly all semidetached binarieshave sensibly circular orbits, which is not true for detached binaries.We carry out simulations with synthetic data to see if semidetachedbinaries can be reliably identified and to quantify the accuracy ofsolutions. The simulations were done for detached as well assemidetached binaries so as to constitute a proper controlled study. Thesimulations demonstrate two additional advantages for semidetacheddistance determination candidates; (4) the well-known difficulty indistinguishing solutions with interchanged radii (aliasing) is much lesssevere for semidetached than for detached binaries and (5) the conditionof complete eclipse (which removes a near degeneracy between inclinationand the ratio of the radii) is identified with improved reliability. Inmany cases we find that parameters are accurately determined (e.g.,relative errors in radii smaller than 10%) and that detached andsemidetached systems can be distinguished. We select 36 candidatesemidetached systems (although seven of these are doubtful because oflarge mass ratios or periods) from the OGLE SMC eclipsing binarycatalog. We expected that most semidetached candidates would have lightcurves similar to those of common Algol binaries, but that turned outnot to be the case, and we note that fully Algol-like light curves arenearly absent in the OGLE sample. We discuss possible explanations forthe near absence of obvious Algols in OGLE, including whether theirpaucity is real or apparent.
| 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.
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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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.
| 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
| Morphologies of Hα Accretion Regions in Algol Binaries
We have investigated a group of 18 Algol-type binaries to determine thegeneral morphologies and physical properties of the accretion regions inthese systems. The systems studied were V505 Sgr, RZ Cas, AI Dra, TVCas, TW Cas, delta Lib, RW Tau, TW Dra, beta Per, TX UMa, U Sge, S Equ,U CrB, RS Vul, SW Cyg, CX Dra, TT Hya, and AU Mon, in order ofincreasing orbital period P=1.18-11.11 days. In addition, the RSCVn-type binary HR 1099 (V711 Tau) was observed to illustrate theappearance of chromospheric Hα emission. Nearly 2200 time-resolvedHα spectra were collected from 1992 March to 1994 December withthe McMath-Pierce Solar Telescope at NSO and mostly with theCoudé Feed Telescope at KPNO. The spectra were obtained at phasesaround the entire orbit of each binary and were closely spaced to permitthe detection of transitions in the profiles. Moreover, the spectra wereobtained typically within three orbital cycles to reduce the influenceof secular variations. Difference profiles were calculated bysubtracting a composite theoretical photospheric spectrum from theobserved spectrum. The analysis of the Hα difference profilesdemonstrates that the accretion structures in Algol binaries have fourbasic morphological types: (1) double-peaked emission systems in whichthe accretion structure is a transient or classical accretion disk; (2)single-peaked emission systems in which the accreted gas was found alongthe trajectory of the gas stream and also between the two stars in anaccretion annulus; (3) alternating single- and double-peaked emissionsystems, which can change between a single-peaked and a double-peakedtype within an orbital cycle; and (4) weak spectrum systems in whichthere was little evidence of any accretion structure since thedifference spectra are weak at all phases. The first two types are thedominant morphologies. The first type can be interpreted physically as adisklike distribution, while the second is a gas stream-likedistribution. The most common type in short-period Algols with 2.7days6 days)were found to have slightly variable but permanent accretion disks atall epochs (i.e., CX Dra, TT Hya, and AU Mon), similar to those found incataclysmic variables. SW Cyg (P=4.57 days) was found to be anintermediate case between the shorter period systems with P<4.5 daysand the longer period group with P>6 days. Two systems, U Sge and UCrB, displayed alternating single- and double-peaked emission atdifferent epochs (Type 3), and changes from one type to another weredetected within a 12 hour time interval. Observations at multiple epochssuggest that four members of the single-peaked emission group, namely RWTau, TX UMa, S Equ, and RS Vul, may actually belong to the alternatinggroup. So, the complete group of alternating systems covers periods of2.7 days
| 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.
| 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.
| Rotation of Algol binaries - a line profile model applied to observations.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996MNRAS.283..613M&db_key=AST
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Doppler Tomography of Accretion Regions in Algol Binaries
The technique of Doppler Tomography has been used to reconstruct imagesof the accretion regions in the short-period Algol-type binaries RS Vul,U Sge, U CrB, beta Per, S Equ, TX UMa and SW Cyg. Hα differenceprofiles of these systems show single and/or double-peaked emissionfeatures at most phases outside of primary eclipse, and absorptionfeatures throughout primary eclipse, except at mid-eclipse. A BackProjection Tomography code was used to generate the sources of Hαemission in the orbital plane of the binary. The tomograms show clearevidence of a gas flow along the predicted free-fall path of the gasstream as well as asymmetric disk-like structures both on and around themass gainer. Another source of Hα emission is associated with thecool magnetically active secondary. The gas stream source was strongestin U CrB while the disk emission was strongest in SW Cyg. Observationsof U Sge in June 1993 show evidence of a strong almost Keplerianaccretion disk, but in June 1994 the emission from this binary waspredominantly from the gas stream. The disk emission seen in the Algolsis reminiscent of that seen in the cataclysmic variables (e.g., U Gem).
| Searching for Intrinsic Variations in Eclipsing Binary Stars
Using a database of nearly 4000 visual estimates made by the authorbetween 1967 and 1993, evidence for intrinsic variations on a time scaleof years is sought after 64 eclipsing binary stars. While none is foundfor most stars, certainb objects warrant further investigation.
| Gravitational radiation and spiralling time of close binary systems (V)
Forty-six binary systems with their primary component masses between 2and 3 solar masses have been considered for gravitational radiationstudy. Power output by gravitational radiation (PB) and spiral timetau(0) for all individual systems have been evaluated. A relation hasbeen given between PB and tau(0). The rate of decrease of orbital periodhas also been given for 10 eccentric orbit systems.
| Photometric study of the binary system S Equ
The Algol-type system S-Equ is observed yielding UBV photoelectric datawhich are examined in terms of the orbit eccentricity of the system. Theobservational data are found to contradict the orbit eccentricity, whilethe mass ratio confirms previous calculations. It is suggested that SEqu is a triple system based on the hypothesis that a third light sourcecomparable to the cooler component can account for the total flux of thesystem.
| 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.
| 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.
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Observation and Astrometry data
| Constellation: | Equuleus |
| Right ascension: | 20h57m12.84s |
| Declination: | +05°04'49.4" |
| Apparent magnitude: | 8.367 |
| Distance: | 396.825 parsecs |
| Proper motion RA: | 14.5 |
| Proper motion Dec: | -0.4 |
| B-T magnitude: | 8.453 |
| V-T magnitude: | 8.375 |
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