The Case for Third Bodies as the Cause of Period Changes in Selected Algol Systems
Many eclipsing binary star systems show long-term variations in theirorbital periods, evident in their O-C (observed minus calculated period)diagrams. With data from the Robotic Optical Transient Search Experiment(ROTSE-I) compiled in the SkyDOT database, New Mexico State University 1m data, and recent American Association of Variable Star Observers(AAVSO) data, we revisit Borkovits and Hegedüs's best-casecandidates for third-body effects in eclipsing binaries: AB And, TV Cas,XX Cep, and AK Her. We also examine the possibility of a third bodyorbiting Y Cam. Our new data support their suggestion that a third bodyis present in all systems except AK Her, as is revealed by thesinusoidal variations of the O-C residuals. Our new data suggest that athird body alone cannot explain the variations seen in the O-C residualsof AK Her. We also provide a table of 143 eclipsing binary systems thathave historical AAVSO O-C data with new values computed from the SkyDOTdatabase.
|
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
|
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.
|
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.
|
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/.
|
CN Andromedae: A Broken-Contact Binary?
We solve new UBV light curves of the eclipsing binary CN Andromedaesimultaneously with radial velocities by the method of differentialcorrections. We find it semidetached with the more massive star fillingits limiting lobe and the less massive star very close to lobe-filling.Our solutions of earlier light curves have the same configuration.Within the uncertainties, the system may be in a broken or a marginalcontact stage as it undergoes thermal relaxation oscillations. The lightcurves are strongly affected by a large dark spot at high latitude onthe more massive star and by a bright substellar spot on the companion.Spot locations and temperatures do not differ significantly from epochto epoch. Based on single star evolutionary models, the primary's mass(1.299+/-0.045 Msolar) and radius (1.425+/-0.016Rsolar) are consistent with those of a star of age2.9×109 yr that will leave the main sequence in another2.0×109 yr. The orbital period has decreased during thepast 50 yr according to traditional eclipse timings and also accordingto our generalized light and velocity solutions that include a referenceepoch T0 and a rate of period change dP/dt. We finddP/dt=-0.01951+/-0.00054 s yr-1, which is consistent withmass transfer from the more to the less massive star of1.4×10-7 Msolar yr-1, assuming nomass is lost from the system. Reliable absolute dimensions aredetermined.
|
ROSAT all-sky survey of W Ursae Majoris stars and the problem of supersaturation
From ROSAT all-sky survey (RASS) data we obtained X-ray fluxes for 57 WUMa type contact systems. In our sample we detected three stars whichare the shortest period main sequence binaries ever found as X-raysources. For stars with (B-V)_0 < 0.6 the normalized X-ray fluxdecreases with a decreasing color index but for (B-V)_0 > 0.6 aplateau is reached, similar to the saturation level observed for single,rapidly rotating stars. The X-ray flux of W UMa stars is about 4-5 timesweaker than that of the fastest rotating single stars. Because earlytype, low activity variables have longer periods, an apparentperiod-activity relation is seen among our stars, while cool stars with(B-V)_0 > 0.6 and rotation periods between 0.23 and 0.45 days do notshow any such relation. The lower X-ray emission of the single, ultrafast rotators (UFRs) and W UMa stars is interpreted as the result of adecreased coronal filling factor. The physical mechanisms responsiblefor the decreased surface coverage differs for UFRs and W UMa systems.For UFRs we propose strong polar updrafts within a convection zone,driven by nonuniform heating from below. The updrafts should beaccompanied by large scale poleward flows near the bottom of theconvective layer and equatorward flows in the surface layers. The flowsdrag dynamo generated fields toward the poles and create a field-freeequatorial region with a width depending on the stellar rotation rate.For W UMa stars we propose that a large scale horizontal flow embracingboth stars will prevent the magnetic field from producing long-livedstructures filled with hot X-ray emitting plasma. The decreased activityof the fastest rotating UFRs increases the angular momentum loss timescale of stars in a supersaturated state. Thus the existence of a periodcutoff and a limiting mass of W UMa stars can be naturally explained.
|
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.
|
HW Persei: an Eclipsing Binary at Critical Contact?
A complete photometric analysis for the eclipsing binary candidate HWPersei is presented. The UBV observations were taken at LowellObservatory in 1996 January. Three epochs of minimum light weredetermined, and an improved linear ephemeris was calculated. The O - Cresiduals, spanning some 60 years, show no evidence of a period change.Standard magnitudes are given, and reddening estimates are made. Thefirst published synthetic light curve solutions of HW Per reveal that itis near a state of critical contact, which we define as both componentsexactly filling their respective Roche lobes. The primary component isof A8 spectral type, and the secondary component is a K3-K4 spectraltype. The nature of the model is discussed.
|
The calculation of critical rotational periods in three typical close binary systems based on synchronization theory.
Not Available
|
My experiences as an astronomer and a survey of binary star research carried out at CASA
Not Available
|
W Corvi, a contact binary with large temperature difference
The star W Corvi seems to be another member of the class of poorlyunderstood close binaries in or near physical contact but far fromthermal contact. Three new photoelectric light curves of W Crv in B andV colours, obtained for the years 1981/82, 1988 and 1993, confirm thatthis short-period (P=0.388 d) eclipsing binary star has substantiallydiffering eclipse depths (0.6 mag brighter at secondary eclipse than atprimary eclipse) and a variable light curve. During 1981, there was nodifference in brightness between the two maxima, but in all other yearswith photoelectric data available, the star was 0.1 mag fainter at phase0.75 than at phase 0.25. The symmetric 1981 light variation can befitted in two fairly different ways, both requiring starspots: the firstis a contact system with the secondary star temperature 83 per cent thatof the primary, but with a bright spot on the inner face (at the neck)of the secondary; and the second is a possibly detached system with thesecondary temperature 95 per cent that of the primary, but with a darkspot on the secondary star directly opposite the neck. The asymmetric1988 and 1993 data require an additional dark spot on the visible sideat phase 0.75. I discuss this star in the context of both evolutionaryand luminosity transfer theory.
|
Near-Contact Binary Systems in the ROSAT All-Sky Survey
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..951S&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.
|
A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
|
Measurement and analysis of rotation in close binaries. II. Calculation of synchronism.
Not Available
|
Near-contact binaries
Not Available
|
The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
Not Available
|
Measurement and Analysis of Rotation in Close Binary Stars - Part One - Observations and Results
Not Available
|
An analysis of Close Binaries (CB) based on photometric measurements (7)
The paper is devoted to the actual problematics in the determination oforbital and physical parameters of active Close Binaries (CB) on thebasis of the interpretation of photometric observations. One solves theproblem in two stages: by obtaining a synthetic light curve in the casewhen the parameters of the corresponding CB model are given a priori(direct problem) and by determining the parameters of the given modelfor which the best fit between the synthetic light curve and theobservations is achieved (inverse problem). In this paper, the aboveprocedure is applied to a particular case of an interpretation of CBlight curves AU Ser and RV Corvi.
|
A summary of the investigations of semi-detached close binaries (1986 - 1988).
The author presents a concise review of the investigations ofsemi-detached close binaries which is based upon the papers included inthe book "Algols" edited by A. H. Batten (1989).
|
Search for contact systems among EB-type binaries. I - TT Herculis
In a search of contact systems among EB-type binaries, the existingphotometric observations of TT Her have been analyzed. An unambiguoussolution, contrary to previous analyses which presented severalpossibilities is found. The system is semi-detached, with the primaryfilling the lobe. There is evidence that the primary is evolved off themain sequence, and that mass transfer is taking place from the primaryto the secondary, which is therefore enlarged by accretion. Thetemperature of the primary component is found to be about 7240 K, thussolving one of the problems for this system. It is concluded that TT Heris the progenitor of an evolved contact binary.
|
Spectroscopic binaries - 15th complementary catalog
Published observational data on the orbital characteristics of 436spectroscopic binaries, covering the period 1982-1986, are compiled intables. The data sources and the organization of the catalog are brieflydiscussed, and notes are provided for each item.
|
A note on thermally decoupled W Ursae Majoris systems
The thermal decoupling degree of short-period contact or near-contactsystems is studied. Statistics of well-observed W UMa systems includingnew beta-light-curve objects was made for thermal-decoupling degree,spectral type, and orbital period. W UMa systems of type A and W arefound to be well characterized by these parameters. W-type objects showa good (linear) correlation in the spectral type vs. thermal-decouplingparameter diagram. This extends to the lower border of the diagram forA-type systems, otherwise scattered in an area of large thermaldecoupling. These empirical facts are analyzed in terms of contact ornoncontact configurations.
|
The evolutionary state of contact and near-contact binary stars
A compilation is presented of the masses, radii, and luminosities of thecomponents of 31 F-K type binary systems which have been found to be incontact or near-contact states. Comparisons of these data with thoseexpected for single stars demonstrates that: (1) the primary componentsof the shallow-contact W-type WUMa systems are unevolved main-sequencestars, while those of the deeper-contact A-type systems are near to theterminal-age main sequence; (2) the secondary components of the W-typesystems have radii of the order of 1.5 times larger than expected fortheir ZAMS masses, while those of the A-type systems have radii of theorder of three times larger; (3) the nine systems in the sample which donot display EW-type light curves can be divided into three marginalcontact systems, five semidetached systems, and one detached system. Theimplications of these findings for the types of evolution into contactare addressed.
|
Contact and near-contact binary systems. V - RV Corvi
Reticon spectroscopy and BVRIc photometry are presented for thelate-type eclipsing binary RV Corvi. The system is found to consist ofan unevolved F2 V primary component and a K type secondary componentwhich has a much larger radius and luminosity than expected for itsmass. The binary may be semidetached, with the primary componentcompletely filling its Roche lobe, or may be in a state of marginalcontact. In order to obtain a solution to the photometric data it wasnecessary to treat the secondary component albedo as a free parameter,yielding a value greater than unity. This result implies that there isan abnormal distribution of luminosity on the surface of the binary,which may be interpreted either as an excess of light on the facinghemisphere of one or both of the components, or as a deficit of light onthe averted hemisphere of the secondary.
|
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).
|
A uvby, beta photometric survey of southern hemisphere
A uvby, beta photometric study of southern hemisphere eclipsing binarystars has been undertaken at Cerro Tololo Inter-American Observatory.The standardized colors and V magnitudes for 288 binaries at quadratureand/or at minimum are presented, along with an indication of theaccuracy of the standardization and photometry. Discussions of theresolving time of the pulse-counting photometers and of the atmosphericextinction at CTIO are included.
|
Close binary systems before and after mass transfer. III - Spectroscopic binaries
A method is presented, for the computation of absolute dimensions fromspectroscopic data on binary systems, which has been adapted for usewith the 7th Catalogue of Batten et al. (1978) and takes into accountseveral results of close binary evolution, with emphasis on the phase ofslow mass transfer during a case B mass transfer. Among the unevolvedsystems, the mass transfer case B is found to be the most abundant typeof interaction. In the set of evolving systems, a subset of 18interacting systems was found with mass ratio near unity, the first starbeing the mass loser as well as the brightest.
|
Revised photometric data for six eclipsing binaries
Using Wood's (1972) model the lightcurves of six eclipsing binaries(V523 Cas, GT Cep, RV Crv, RU Eri, UV Psc, and V499 Sco) whose generalproperties have not yet been discussed adequately have been reanalyzed.For all binaries (except UV Psc) photometric elements appreciablydifferent from those previously deduced from the same observationalmaterial have been derived, while a more consistent interpretation ofthe binaries studied has been achieved. The W UMa-type binary V523 Casappears to be a contract system of the W-type subclass. GT Cep is foundto be a normal semidetached system. RV Crv is very likely to be anevolved contact binary, whereas RU Eri may also be related to thecontact systems. The early-type binary V499 Sco and the RS CVn binary UVPsc turn out to be detached systems with main-sequence components.
|
