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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.
| B.R.N.O. Contributions #36, Times of minima
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| BAV-Results of Observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Evolutionary Status of RV Trianguli and its Related Algol-Type Binaries
We present CCD photometry for the Algol-type binary RV Trianguliobserved during three nights in 2007 November. The photometric solutionwas derived from our VR observations by using the Wilson-Devinnyprogram. The results indicated that RV Tri is a semidetached binary witha mass ratio of q = 0.306 (± 0.005). Based on 236 light minimumtimes, the orbital period change of RV Tri was analyzed in detail. Wediscovered that a secular decrease exists with two cyclic variations.The long-term period decreases at a rate of dP/dt = -6.07 ×10-8days yr-1, which may be due tomass and angular momentum loss. Two cyclic variations (i.e., P3 = 25.34 yr and A 3 = 0fd0029, and P 4= 10.30 yr and A 4 = 0fd0026) may be attributed to the unseenthird and fourth bodies, respectively, which can be weakly identified bythe photometric solution. If the existence of the two additional bodiesis true, this binary may be a quadruple star. From 22 Algol binarysystems with orbital periods decreasing, the relations of P -dP/dt and P - f were determined. With the orbital period decrease,dP/dt also decreases, indicating that mass and angular momentum losswill become slower. However, the fill-out factor of the primary f willincrease as the period decreases, which will finally result in theprimary filling its Roche lobe. Therefore, this kind of binary willevolve into a contact configuration.
| Recent Minima of 184 Eclipsing Binary Stars
This paper continues the publication of times of minima for eclipsingbinary stars from observations reported to the AAVSO Eclipsing BinaryCommittee. Times of minima from observations made from March 2008through August 2008 are presented.
| 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
| B.R.N.O. Contributions #34
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| TZ Lyrae: an Algol-type Eclipsing Binary with Mass Transfer
We present a detailed investigation of the Algol-type binary TZ Lyrae,based on 55 light minimum timings spanning 90 years. It is found thatthe orbital period shows a long-term increase with a cyclic variationsuperimposed. The rate of the secular increase is dP/dt=+7.18×10^{-8} d yr^{-1}, indicating that a mass transfer from the less massivecomponent to the more massive one at a rate of dm=+2.21×10^{-8}M_? yr^{-1}. The cyclic component, with a period of P_{3}=45.5 yrand an amplitude of A=0.0040°, may be interpreted as either thelight-time effect in the presence of a third body or magnetic activitycycles in the components. Using the latest version Wilson-Devinney code,a revised photometric solution was deduced from B and V observations.The results show that TZ Lyr is an Algol-type eclipsing binary with amass ratio of q=0.297(±0.003). The semidetached configurationwith a lobe-filling secondary suggests a mass transfer from thesecondary to the primary, which is in agreement with the long-termperiod increase of the binary system.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| New Times of Minima of Some Eclipsing Binary Stars
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| 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.
| The Near-Contact Binary RU Ursae Minoris
The near-contact binary RU UMi with an F0-type primary and a K-typesecondary was observed in 2003. With the latest version of theWilson-Devinney code, the photometric elements were computed. Theresults reveal that RU UMi is a semi-detached system with the secondarycomponent filling its Roche lobe, which should lead to an increase ofthe period for conservative mass transfer between the two components.However, an orbital period analysis shows that the orbital period ofthis system undergoes a continuous decrease at a rate ofdP/dt=-1.72×10-8d yr-1. Therefore, thecontinuous period decrease may demonstrate that the system isnonconservative. This can result from a combined effect of mass transferfrom the secondary component to the primary one and mass and angularmomentum loss from the system. With the secular mass and angularmomentum losses, RU UMi may evolve from the present short-periodnear-contact system into an A-type contact binary.
| New CCD Times of Minima of Eclipsing Binary Systems
We present a total of 208 CCD timings for 103 eclipsing binaries.
| 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.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| 163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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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/.
| 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
| 162-nd List of Minima Timings of Eclipsing Binaries by BBSAG Observers
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| CCD Minima for Selected Eclipsing Binaries in 2002
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| 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.
| Orbital Period Studies of Two Algol-Type Eclipsing Binary Systems: TY Pegasi and X Trianguli
O-C curves of two EA-type eclipsing binaries, TY Peg and X Tri, areformed and studied in detail based on all available times of lightminimum. For TY Peg, it was discovered that the general trend of the O-Ccurve showed a downward parabolic variation, which indicates a secularperiod decrease with rate at dP/dt=-1.16×10-6 daysyr-1. When the secular decrease is removed from the O-Ccurve, the residuals can be described by several linear ephemerides,suggesting several sudden period jumps. For the other one, X Tri, it isfound that the general O-C trend also indicates a secular perioddecrease (dP/dt=-1.42×10-7 days yr-1), andseveral irregular period jumps are found to superpose on the long-timeperiod decrease. This kind of period change, irregular sudden jumpssuperposed on secular decrease, is typical for many other Algol-typebinary systems such as TU Her, UU And, Z Per, Y Psc, BO Mon, FH Ori, RTPer, and TX UMa. The period changes of these systems may be caused byorbital angular momentum loss via variable magnetic coupling and gravitycoupling between the components.
| 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.
| Possible Mass and Angular Momentum Loss in Algol-Type Binaries. V. RT Persei and TX Ursae Majoris
The changes in the orbital periods of two EA-type eclipsing binaries, RTPer and TX UMa, are studied in detail, based on the analysis of theirtimes of minimum light. For RT Per, it is shown that the trend of theO-C curve can be described by a parabola opening at the bottom, whichindicates a secular period decrease at the ratedP/dt=-9.29×10-8 days yr-1. By subtractingthe secular decrease in the O-C curve, the residuals display anoscillatory variation that can either be described by a continuousperiodic change, indicating the presence of a third body, or by severallinear ephemerides, indicating several sudden period jumps. Since theoscillatory change is not strictly periodic, the latter is moreplausible, which suggests that several irregular period jumps aresuperposed on the long-term period decrease. For the other object, TXUMa, it is discovered that the O-C trend also suggests a secular perioddecrease (dP/dt=-7.13×10-7 days yr-1), andfive irregular period jumps are found superposed on the secular perioddecrease. This kind of period is not unique for Algol-type binarysystems. The period changes, both the secular decrease and the suddenjumps, can be plausibly explained by orbital angular momentum loss viamagnetic coupling and gravity coupling between the components.
| 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
| 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.
| Orbital period changes and possible mass and angular momentum loss in two Algol-type binaries: RW Coronae Borealis and TU Herculis.
The orbital period of two Algol-type binaries, RW CrB and TU Her, arestudied. It is discovered that the orbital period of RW CrB shows asecular decrease at the rate of dP/dt = -4.29×10-8 daysyr-1 while the orbital period of TU Her varies in somecomplex way. Two jumps in the orbital period are found while itundergoes secular decrease at a rate of dP/dt =-2.92×10-6 days yr-1. The rates of decreaseof the orbital periods dP/dt in other Algol-type binaries are revisedand the statistical relation between the orbital period P and its rateof change dP/dt is also discussed. The properties of the changes in theorbital period of these systems, combined with their semidetachedconfigurations, demonstrate that they may be undergoing secular mass andangular momentum loss (AML) during their evolution. The irregular abruptchanges that are superposed on the secular decrease of the orbitalperiod may be caused by some instabilities during the mass transfer andAML.
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