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The Banana Project. III. Spin-Orbit Alignment in the Long-period Eclipsing Binary NY Cephei
Binaries are not always neatly aligned. Previous observations of the DIHer system showed that the spin axes of both stars are highly inclinedwith respect to one another and the orbital axis. Here, we report on ameasurement of the spin-axis orientation of the primary star of the NYCep system, which is similar to DI Her in many respects: it features twoyoung early-type stars (~6 Myr, B0.5V+B2V), in an eccentric andrelatively long-period orbit (e = 0.48, P = 15fd3). The sky projectionsof the rotation vector and the spin vector are well aligned(?p = 2° ± 4°), in strong contrast to DIHer. Although no convincing explanation has yet been given for themisalignment of DI Her, our results show that the phenomenon is notuniversal, and that a successful theory will need to account for thedifferent outcome in the case of NY Cep.Based on observations made with Sophie, a high-resolution échellespectrograph on the 1.93 m telescope of the Observatoire deHaute-Provence.
| The most plausible explanation of the cyclic period changes in close binaries: the case of the RS CVn-type binary WW Dra
Cyclic period changes are a fairly common phenomenon in close binarysystems and are usually explained as being caused either by the magneticactivity of one or both components or by the light travel time effect(LTTE) of a third body. We searched the orbital period changes in 182EA-type (including the 101 Algol systems used by Hall), 43 EB-type and53 EW-type binaries with known mass ratio and spectral type of thesecondary component. We reproduced and improved the diagram in Hallaccording to the new collected data. Our plots do not support theconclusion derived by Hall that cyclic period changes are restricted tobinaries having a secondary component with spectral type later than F5.The presence of period changes among systems with a secondary componentof early type indicates that magnetic activity is one, but not the only,cause of the period variation. It is discovered that cyclic periodchanges, probably resulting from the presence of a third body, are morefrequent in EW-type binaries among close systems. Therefore, the mostplausible explanation of the cyclic period changes is the LTTE throughthe presence of a third body. Using the century-long historical recordof the times of light minimum, we analysed the cyclic period change inthe Algol binary WW Dra. It is found that the orbital period of thebinary shows a ~112.2-yr cyclic variation with an amplitude of ~0.1977d.The cyclic oscillation can be attributed to the LTTE by means of a thirdbody with a mass no less than 6.43Msolar. However, nospectral lines of the third body were discovered, indicating that it maybe a candidate black hole. The third body is orbiting the binary at adistance closer than 14.4 au and may play an important role in theevolution of this system.
| Recent Minima of 155 Eclipsing Binary Stars
The AAVSO's publication of times of minima for eclipsing binary stars has shifted from the recent publication series, Observed Minima Timings of Eclipsing Binaries, Number 1-12, back to the JAAVSO. Times of minima fromobservations made in the past eight months are presented. New lightelements for AC CMi have been calculated from recent AAVSO observations:Min(JD) = 2451978.7504 + 0.867216691 E± 0.0004 ± 0.00000024
| Third-Body Parameters from Whole Light and Velocity Curves
Eclipsing binaries can improve multiple system statistics via thelight-time effect and radial velocity shifts. Here an algorithm operateson data of mixed type to exploit these opportunities. Main reasons forenhanced reliability are that (1) combined light and velocity curvesgive better timewise coverage than either type alone, (2) properlyweighted solutions impersonally balance light and velocity information,and (3) the entire theory is within the computer model, so observationsare used directly without corrections. A brief history of mixedwhole-curve solutions is given and the relative importance of light-timeand radial velocity input for third-body parameters is discussed andquantified. Period sifting by power spectral analysis is essentiallyindispensable in preliminary work. Applications are to the Algol-typesystem DM Persei and the detached system VV Orionis. An assumption ofcoplanarity for DM Per's inner and outer orbits is tested and quantifiedby dynamical experiments. Derived third-body parameters for DM Per aremainly reasonable and self-consistent. For comparison with whole-curveresults, we also investigated DM Per's ephemeris in terms of eclipsetimings and found whole-curve solutions to give smaller standard errorsin reference epoch (T0), binary orbit period (P), and dP/dt,over a similar baseline in time. An astonishing outcome is lack ofevidence that can pass reasonable validity tests for VV Ori'swell-accepted third star with P~120 days. Estimates of third light doindicate a third star, but the correct period cannot now be established,so the star cannot be identified as the one heretofore recognized fromradial velocity evidence. The much cited 120 day period appears to be anartifact of the window function for VV Ori's historical velocityobservations.
| 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.
| Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
| 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/.
| 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
| 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.
| 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.
| TRY Geminorum - Revised Elements
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..800S&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.
| 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.
| An astrometric catalogue of stars in the region of M15
We present positions and proper motions with respect to the PPMcatalogue of 863 stars in a field of 8 deg x 6 deg centered on theglobular cluster M15. The catalogue is based on measurements of 136plates from the Carte du Ciel telescope of Bordeaux, the CERGA Schmidttelescope, and the double refractor of Bonn. The modal accuracy of theproper motions is +/- 0 arcsec 15/100 a.
| A high galactic latitude survey of far-ultraviolet excess objects
This study presents optical spectra obtained for a selection of objectsincluded in a catalog of far UV-bright, high-galactic-latitude objectsdetected with a balloon-borne survey telescope. The observed objectsprovide a sample of subdwarf O and B stars, white dwarfs, and binarysystems including a hot subluminous member. Model-atmospheres analysisof the subdwarf sample is used to determine the temperature, gravity,and helium-to-hydrogen ratio of the individual objects. A smoothdistribution of objects is found on the gravity-versus-temperaturediagram near the theoretical location of the extended horizontal branch.A break between the helium-rich and helium-poor objects is found tooccur at 40,000 K. Suspected binary objects were identified and analyzedto determine the temperature and gravity of the hot subluminous memberin each system. The number of subdwarf stars contained in the binariesis determined at 65 to 100 percent. The proportion of white dwarfs thatexperience the subdwarf phase of evolution is found to be 0.94 percent.
| 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.
| Accuracy and efficiency in the binary star reflection effect
The geometric and irradiation heating problems for the binary starreflection effect theory are developed in terms of equipotential levelsurfaces and are sufficiently general so as to include eccentric orbitsand nonsynchronous (even centrifugally limited) rotation and to treatmultiple reflection. The requisite physics, mathematics, and logic arethen presented and the computations are organized so that a givenquantity is computed only as often as necessary, emphasizing thedistinction between local surface quantities and aspect-relatedquantities. The local geometric, bolometric, and wavelength-specificquantities are grouped for storage according to how often they need tobe recomputed. Some tests of a computer program based on this reflectionmodel are given in the form of graphs in which program results arecompared to a special exact case, and with results from an earlierprogram. The new program gives intuitively reasonable output for alltests, and the tests give an idea of how accurate the old program is,adopting the detailed reflection computations of the new program as astandard for comparison. A table is given which shows the convergence ofthe multiple reflection computations to a constant distribution ofsurface effective temperature.
| Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
Not Available
| An Updated List of Eclipsing Binaries Showing Apsidal Motion
Not Available
| Rotation rates from Algol-type light curves - SW Cygni, AQ Pegasi, and AW Pegasi
Exploitation of a recently developed means of deriving binary-componentrotation rates from light curves is continued for three rapidly rotatingAlgol-type systems, which were selected for their known or suspectedfast rotation, as part of a long-term program to improve the rotationstatistics of Algols. The primary components of SW Cygni and AQ Pegasiappear to fill their limiting rotational lobes (i.e., the systems aredouble-contact binaries). The third binary, AW Pegasi is found to beclose to double contact. An uncertainty common to all of these systemsis that of whether the primary star's spectral lines are photospheric ordue to orbiting gas. Comments are made concerning the expected effectsof circumprimary gas on light-curve and line-profile estimates ofrotation rates.
| Gravitational wave spectra from eccentric binaries - A preliminary census
Gravitational waves (GW) from binary stars are promising candidates forGW detection experiments. The spectral distribution of GW bathing theearth from a set of 1048 binary stars has been computed, and the resultsare presented. Orbital eccentricity and all relevant harmonics areincluded.
| 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.
| Absolute parameters of stars in semidetached eclipsing binary systems
A number of questions concerning the absolute parameters of stars insemidetached binary systems are addressed. Consideration is given to:similarities between Algol-type binaries and unevolved detached binarieswith respect to the mass-luminosity law; and the single-line classicalAlgol candidates with known mass functions and photometric solutions formass ratio. It is shown that the validity of the mass luminosity-lawcannot be verified for individual Algol-type binaries though it doeshold well on average; and (2), the existence of a definite class ofsd-binaries not containing a proportion of significantly undersize typesis apparent. The conclusions are found to be in general agreement withthe observations of Hall and Neff (1979).
| A Catalogue of Classical Evolved Algol-Type Binary Candidate Stars
Not Available
| Revised elements and evolutionary status of six eclipsing binary stars
Twelve photoelectric light curves of six eclipsing binary stars namelyGG Cas, WX Cep, UZ Cyg, VW Cyg, AQ Peg and ST Per in two differentfilters (B and V for the first five binaries and R and I for ST Per)have been analysed by Kopal's new method of analysis of the light curvesof eclipsing system in the frequency domain. The elements of the systemshave been evaluated and their evolutionary status discussed.
| A study of the O'Connell effect in the light curves of eclipsing binaries
In the present consideration of O'Connell's (1951) study of the lightcurve asymmetry between outside eclipse maxima, using UBV photoelectricdata, parametric and nonparametric methods indicate significantcorrelations in at least one color between the size of the asymmetry, onthe one hand, and several additional parameters. These include: thecolor index of the asymmetry, the relative sizes of the hotter andsmaller components, and their distortion, the relative separation of thestars, and the logarithm of the period. The present study data arecharacterized by lower mean amplitudes and a much more even distributionof the asymmetry, with respect to sign, than that of O'Connell, andthere is a tendency for the brighter maximum to be redder, contrary toO'Connell's results. More than one mechanism for the O'Connell effect issuggested.
| 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).
| Mass transfer in close binary systems - Original and remnant masses
Masses of numerous Algol binaries (and a few Wolf-Rayet systems) arecompared with new theoretical predictions in which the effect ofovershooting in stellar interiors is considered. The comparison appearsto confirm that usual mass-transfer computations cannot satisfactorilyaccount for the observed masses of the post-mass exchange remnants. Itis suggested that the incongruities which hinder a quantitativeevaluation of the amount of mass loss from close binaries may be relatedto the possible occurrence of complicated interactive processes,including phases of contact configurations, which might drasticallymodify the outcome of mass-transfer processes.
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