WZ Cephei: A Close Binary at the Beginning of Contact Phase
Photometric photoelectric data of the short-period close binary system,WZ Cephei, are presented. A new photometric analysis with the 2003version of the Wilson-Devinney method confirmed that it is a shallowcontact binary (f ~ 13.3%) with a high level of spot activity on theprimary component. Combining new determined times of light minimum withthe others published in the literature, the period change of the binarystar is investigated. A periodic variation, with a period of 34.2 yearsand an amplitude of 0fd013, was discovered to be superimposed on along-term period decrease (dP/dt = –8.8 ×10–8 days year–1). Both the secularperiod decrease and the shallow contact configuration suggest that thisbinary system is at the beginning of contact phase. It is on the way toevolving into a normal overcontact phase via secular angular momentumloss and/or mass transfer from the more massive component to the lessmassive one. The period oscillation can be explained either by thelight-time effect due to the presence of a third body or by magneticactivity. On the one hand, if it is caused by the light-time effect, themass and the orbital radius of the additional body should be m3 = 0.17 M sun and a 3 = 26.6 AU,respectively, when this body is coplanar to the orbit of the eclipsingpair. On the other hand, since the system shows high levels of spotactivity, the period oscillation may be explained as a consequence ofmagnetic cycles. In this case, the required variation of the quadrupolemoment is calculated to be 9.2 × 1049 g cm2.
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Catalogue of Ap, HgMn and Am stars
We present a catalogue of 8205 known or suspected Ap, HgMn and Am stars.This paper is a major update of our first edition of the catalog of Apand Am stars and includes revised identifications, additional stars andrevised information obtained from the literature.Catalogue (full Table 1) is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/498/961
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Near-Contact Binaries with Mass Transfer: V473 Cassiopeiae and II Persei
Photometric solutions of two short period close binaries, V473 Cas andII Per, are derived with the 2003 version Wilson-Van Hamme code. It isshown that V473 Cas is a semidetached system with the primary componentor the secondary component at its critical Roche Lobe, while II Per is amarginal contact binary system with both components filling theircritical Roche Lobes, but with a large temperature difference betweenthe two components. Both systems belong to near-contact binaries withthe light curves enhanced around the left shoulder of secondary minimum,which can be explained by hot spots on the secondary components due tothe mass transfer via a stream hitting the facing surface of thesecondary components. The orbital period investigations based on allavailable times of light minimum show a secular period existing in thesetwo targets decreasing at the rate of dP/dt = –7.61 ×10–8 days yr–1 for V473 Casand dP/dt = –7.54 ×10–8 days yr–1 for II Per.The decrease of the orbital period can be the result of mass transferfrom the primary component to the secondary one, which is consistentwith the asymmetric light curves of V473 Cas and II Per. Therefore, V473Cas and II Per are other examples displaying evidence of mass transferbetween the two components. We have collected NCBs with secular periodvariation and find that almost all SD1-type NCBs show decreasing periodsand enhancing luminosity on the left shoulder of secondary minimum intheir light curves. So the semidetached configuration with the lobefilling primary is more plausible for V473 Cas. Furthermore, thedetected enhancing amplitude of luminosity for SD2-type NCBs is smallerthan other types of NCBs, which implies that the mass transfer from theprimary component to the secondary one is stronger than the transfer inopposite direction. With the orbital period decrease, V473 Cas and IIPer will evolve into overcontact binaries with true thermal contact.
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B.R.N.O. Contributions #34
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A Photometric Study of the Near Contact Binary UU Lyncis
The near-contact binary UU Lyn with an F3V-type primary was observed in2005 and 2006. With the latest version of the Wilson-Devinney code, thephotometric elements were computed. The results reveal that UU Lyn is amarginal contact system with a large temperature difference of about1900 K between the primary and secondary components. All availableeclipse times, including new ones, were used in the analysis. Theresults show that the orbital period of this system undergoes acontinuous decrease at a rate of dP/dt=-1.84×{10^{-8}} d yr^{-1}.With the period decrease, UU Lyn may evolve from the presentshort-period marginal contact system into a contact system with truethermal contact. This target might just be undergoing the cyclespredicted by the theory of thermal relaxation oscillations (TRO). It isan interesting example resembling BL And, GW Tau, ZZ Aur, KQ Gem, CN Andand AD Cnc, that lie in the key evolutionary stage.
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Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
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HL Aurigae: A pre-contact binary system with a solar-mass companion
Orbital period changes of the near-contact binary (NCB) system, HLAurigae, are analyzed based upon all the published CCD and photoelectrictimes of light minimum. It is found that the period of HL Aurigae showsa small-amplitude cyclic oscillation with a period of 6.5 years and anamplitude of 0.d0058 while it undergoes a secular decrease ata rate of dP/dt = ‑1.08 × 10‑7 days/year.The cyclic period oscillation can be interpreted either by thelight-time effect of a third body or by magnetic activity cycles of thecomponents. Since the third-body assumption is in agreement with thepresence of a large amount of third light in the system discovered by ,we think that HL Aurigae may be a true triple system. In order to deducea G2-type third companion as proposed by , the orbital inclination ofthe third body should be i′ = 40°, which is much smaller thanthat of the eclipsing pair (i = 85.°7). This suggests that the thirdcompanion is not coplanar with the eclipsing binary. This may indicatethat the solar-mass component may be captured by the eclipsing binarysystem in some previous stages of its formation and evolution. HLAurigae is a short-period NCB with a F1V-type primary and a G9V-typesecondary component and both of the components are filling or nearlyfilling their Roche lobes. As the period is decreasing, the shrinking ofthe Roche lobe will finally cause it to evolve into a contact binarysystem in the timescale of 2.1 × 106 years. Theperiod decrease may be caused by mass transfer or/and by angularmomentum loss via magnetic braking.
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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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CCD Times of Minima of Selected Eclipsing Binaries
682 CCD minima observations of 259 eclipsing binaries made mainly byauthor are presented. The observed stars were chosen mainly fromcatalogue BRKA of observing programme of BRNO-Variable Star Section ofCAS.
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A Period Study of the Near-Contact Binary IR Cassiopeiae
The near-contact binary IR Cas was observed in 2003 October. Two newobserved times of the primary minimum were derived. All of the availableeclipse times, including the new ones, spanning 90 years were analyzed.It was shown that the period change of the system is very complex. Aperiod oscillation with a period of 53.24 years and an amplitude ofabout 0.0133 days were found, while it undergoes a secular decrease at arate of dP/dt = -1.18 × 10-7(±0.09)dyr-1. The mechanisms that could explain the period changesand the evolutionary state of the system are discussed.
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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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Short-period near-contact binary systems at the beginning of the overcontact phase
A detailed analysis of orbital period changes of seven near-contactbinary stars (NCBs) (BL And, V473 Cas, XZ CMi, BV Eri, RU Eri, UU Lynand GR Tau) with period less than 1 d has been performed and theirrespective O-C diagrams are formed and discussed. It is found that allsystems analysed show secular period decreasing. For V473 Cas, theanalysis of the period change was performed based on data collected byMoschner, Frank & Bastian. For XZ CMi, its period shows some complexchanges, a possible cyclic oscillation is discovered to superpose on thesecular decrease that can be explained either by the presence of a thirdbody or by magnetic activity cycles of the components. Since thethird-body assumption is consistent with the photometric solution ofRafert, XZ CMi may be a truly triple system. For BV Eri, the perioddecrease is only supported by weak evidence. All the seven systems areshort-period NCBs with AF-type primary components where both componentsare filling or nearly filling the critical Roche lobe. As the perioddecreases, the separation between both components will be reducing andthus these systems will evolve into A-type overcontact binaries. Theperiod decrease may be caused by mass transfer or/and by angularmomentum loss via magnetic braking. Combined with the published data onthe other systems of the same type, a possible statistical connectionbetween orbital period P and its rate of decrease dP/dt is obtained:dP/dt=-5.3 × 10-7×P+ 1.3 × 10-7d yr-1. This correlation indicates that the smaller theorbital period P is, the smaller its rate of change dP/dt will be. Thecorrelation found in this paper indicates that there may be a smoothtransition from A- and F-type NCBs with period decreases to the A- andF-type overcontact binaries that have period increases, and in thatsense one may postulate that the NCBs may be the progenitors of theA-type W UMa systems and will be oscillating around a marginal-contactstate as predicted by thermal relaxation oscillation (TRO) theory.
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Observational evidence and analysis of the coupling between the dynamical and the thermodynamic processes for close binaries.
Analytical methods of the orbital period, the types of its variations,the mechanisms causing the changes in the orbital period, and problemsand progresses in the orbital period study are introduced. Theproperties of the variations in te orbital period and in the lightcurve, and the connections between the changes of the orbital period andthe light curve in different types of close binaries are also reviewed.The changes of the orbital period, the variations of the light curve andtheir connections in some sample stars are studied. The statisticalrelation of the parameters in contact binaries is also investigated.
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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.
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Changes in the orbital period of the near-contact binary BF Vir.
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AV Hydrae: a near-contact semi-detached binary with possible mass and angular momentum loss.
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Do the physical properties of Ap binaries depend on their orbital elements?
We reveal sufficient evidence that the physical characteristics of Apstars are related to binarity. The Ap star peculiarity [represented bythe Δ(V1-G) value and magnetic field strength] diminishes witheccentricity, and it may also increase with orbital period(Porb). This pattern, however, does not hold for largeorbital periods. A striking gap that occurs in the orbital perioddistribution of Ap binaries at 160-600d might well mark a discontinuityin the above-mentioned behaviour. There is also an interestingindication that the Ap star eccentricities are relatively lower thanthose of corresponding B9-A2 normal binaries for Porb>10d.All this gives serious support to the pioneering idea of Abt &Snowden concerning a possible interplay between the magnetism of Apstars and their binarity. Nevertheless, we argue instead in favour ofanother mechanism, namely that it is binarity that affects magnetism andnot the opposite, and suggest the presence of a newmagnetohydrodynamical mechanism induced by the stellar companion andstretching to surprisingly large Porb.
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CP2 stars as viewed by the UVBY H_beta system
The aim of this work is to study the capacity of the uvby H_βsystem for detecting the chemically peculiar (CP) stars based on theeffect that peculiar features in the flux distribution have on all theStromgren-Crawford indices. Our study focuses on the classical magneticpeculiar stars (CP2), though Am stars (CP1) are also included forcomparison with cool CP2 stars. Satisfactory results were obtained forhot CP2 stars: the definition of a new index p, which is a linearcombination of uvby H_β colours, allowed us to separate a highpercentage of hot CP2 stars from normal stars. According to this newindex, 60 new CP2 candidates are proposed. The working sample wasextracted from The General Catalogue of Ap and Am stars by \cite[Rensonet al. (1991)]{ren91}. Photometric observations to enlarge the sample ofCP2 stars with complete uvby H_β photometry were carried out. Theseobservations are also reported in the present paper. The new index p isalso used to correct the reddening of early CP2 stars computed as ifthey were normal stars. Tables 2, 3 and 7 are also available inelectronic form from CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
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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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Near-contact binaries
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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.
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Statistical Study on the Semidetached and Near Contact Semidetached Binary Systems
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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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Revised photometric elements of BF VIR
The B light curve of BF Vir published by Mallama and Witt (1976) hasbeen re-analyzed using the Wilson and Devinney (1971) approach, and theabsolute dimensions have been computed. The system turns out to be asemi-detached system, with an A2V primary and an evolved G2 undermassivesecondary which fills its Roche lobe; the primary, even if detached, isnot far from contact.
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New ephemerides for 120 eclipsing binary stars
Abstract image available at:http://adsabs.harvard.edu/abs/1980ApJS...44..241M
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A catalogue of parameters for eclipsing binaries
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Seventh catalogue of the orbital elements of spectroscopic binary systems.
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Minima of Eclipsing Variables
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A study of the eclipsing variable BF Virginis
Two photoelectric light curves of BF Vir, obtained five years apart, arerectified and solved for the geometric elements. The light curves aremoderately complicated by ellipticity of the components and reflectioneffects. The solution indicates that the spectroscopically invisiblesecondary component may be an evolved star with a surface temperaturearound 5000 K. One of the component stars may have an ultravioletanomaly. The revolution period of the system has remained constantwithin about one part in 100,000 since 1930, but a larger change mayhave occurred before then.
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INHABITED SKY
