Period study of TW Draconis
Context: TW Draconis is one of the most well known Algol-type eclipsingbinaries. There is significant evidence for miscellaneous interactingphysical processes in the system, which manifest themselves as forexample period and light curve changes. We study time series data forthe star accumulated over the past 150 years to detect changes in minimatimings. Aims: Using 561 available minima timings, we compile anextended O-C diagram analysis. A detailed description of period changesallows us to construct the true phased light curve at any moment. Methods: By applying weighting nonlinear robust regression the timingresiduals were analysed. The weights of individual types of minima weredetermined iteratively. The ephemeris are expressed in the orthogonal orquasi-orthogonal forms allowing us for example to determine directlyuncertainties of photometric phases for any given moments. Results: The timing residuals (according to the linear ephemeris)display two stages of differing behaviour in 1858-2007. The first partends around 1942. It is characterised by more or less smoothlinear/parabolic course of timing residuals. In 1858-1905, the periodwas almost constant P=2.806513(9)d, but, in 1905-1942, the periodincreased with the rate of 5.69(5)×10-8 dyear-1. We interpret this as a result of continuous massexchange between components at the mean rate of6.9×10-7 M? year-1. Since1942, the system has been showing alternating and shortening periodchanges with the length of a cycle of about two decades, modulated byshort-term periodic variations. The latter small variations with theperiod 6.5 years are caused by the light-time effect due to the presenceof a third low-mass body in the system. Major oscillations can beexplained as consequences of quadrupole moment variation in the system.Table 1 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/489/321
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Comparative statistics and origin of triple and quadruple stars
The statistics of catalogued quadruple stars consisting of two binaries(hierarchy 2 + 2), is studied in comparison with triple stars, withrespective sample sizes of 81 and 724. Seven representative quadruplesystems are discussed in greater detail. The main conclusions are asfollows. (i) Quadruple systems of ? Lyr type with similar massesand inner periods are common, in 42 per cent of the sample the outermass ratio is above 0.5 and the inner periods differ by less than 10times. (ii) The distributions of the inner periods in triple andquadruple stars are similar and bimodal. The inner mass ratios do notcorrelate with the inner periods. (iii) The statistics of outer periodsand mass ratios in triples and quadruples are different. The medianouter mass ratio in triples is 0.39 independently of the outer period,which has a smooth distribution. In contrast, the outer periods of 25per cent quadruples concentrate in the narrow range from 10 to 100yr,the outer mass ratios of these tight quadruples are above 0.6 and theirtwo inner periods are similar to each other. (iv) The outer and innermass ratios in triple and quadruple stars are not mutually correlated.In 13 per cent of quadruples both inner mass ratios are above 0.85(double twins). (v) The inner and outer orbital angular momenta andperiods in triple and quadruple systems with inner periods above 30dshow some correlation, the ratio of outer-to-inner periods is mostlycomprised between 5 and 104. In the systems with small periodratios the directions of the orbital spins are correlated, while in thesystems with large ratios they are not. The properties of multiple starsdo not correspond to the products of dynamical decay of small clusters,hence the N-body dynamics is not the dominant process of theirformation. On the other hand, rotationally driven (cascade)fragmentation possibly followed by migration of inner and/or outerorbits to shorter periods is a promising scenario to explain the originof triple and quadruple stars.
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236 Minima Timings of Eclipsing Binaries Observed by Integral OMC
236 times of minima of 97 eclipsing binaries observed by ESA INTEGRALOMC are presented.
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A period study and light-curve synthesis for the Algol-type semidetached binary XXCephei
We obtained CCD photometric observations of the Algol-type semidetachedbinary XXCephei (XXCep) during 15 nights from 2002 September 17 to 2003February 2, and also on 2005 January 21. Except for those data taken onthe last night of the concentrated observing season, the 3881measurements were obtained over an interval of only 106 nights. Fromthese data, four new times of minimum light were calculated. The (O- C)diagram formed from all available timings, and thus the orbital periodof the system, can be partly represented as a beat effect between twocyclical variations with different periods (yr, yr) and amplitudes(K1=0.015d, K2=0.103d), respectively. Bothphysical and non-physical interpretations of these cycles wereinvestigated. The long-term sinusoidal variation is too long formagnetic cycling in solar-type single and close binary stars. Inaddition, we have studied the effect of a possible secular periodvariation. By analysing the residuals from our Wilson-Devinney (WD)binary model, we found small light variations with a period of 5.99dwith amplitudes growing toward longer wavelengths. We think that theseoscillations may be produced by instabilities at the systemicL1 point (also occupied by the point of the cool star) andthat these instabilities are, in turn, caused by non-uniform andsporadic convection. There is also a short-period oscillation of about45min in the WD light residuals that is attributed to accretion on tothe mass-gaining primary component from a feeble gas stream originatingon the cool donor star.
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Orbital period variations of four Algol-type eclipsing binaries: SW Cyg, UU Leo, XX Cep and BO Vul
The orbital period behaviours of four Algol-type eclipsing binaries SWCyg, UU Leo, XX Cep and BO Vul are studied, by using all available timesof minimum light in the literature. Their O-C diagrams were representedby long-period sinusoidal variations superimposed on parabolic forms.The parabolic forms for SW Cyg and UU Leo correspond to secular periodincreases, while for XX Cep and BO Vul to secular period decreases. Toexplain these observed secular changes in these four Algol systems, weconsidered the combined effect of the mass transfer from the lessmassive component to the more massive one and the mass loss from thesystem. We concluded that the dominant mechanism for observed long-termperiod change of SW Cyg and UU Leo is the mass transfer, and that of XXCep and BO Vul is the mass loss from the systems. It is interesting thatthe mass transfer rates (i.e., 10-7-10-8M\sun/yr) found for all four Algol binaries are at the upperlimit of those generally accepted for Algols. However, assuming the massloss via circumbinary disks of Chen et al. (2006) reduces the rate to10-8-10-9 M\sun/yr. We interpreted thetilted sinusoidal variations in all cases in terms of the light-timeeffect due to unseen components in the systems. Unacceptably largehypothetical third body masses in the case of SW Cyg and UU Leo, andcommon nature of the cyclic O-C variations in semi-detached Algolsrecall the cyclic magnetic activity effects of the secondary componentsas the working hypothesis in explaining cyclic period variations ofthese systems.
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Visual Minima Timings of Eclipsing Binaries Observed in the Years 1992 - 1996
The paper contains a list of 283 new times of minima and 77 revisedtimes of minima for 63 eclipsing binaries derived by the author fromhis visual observations.
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New Times of Minima of Eclipsing Binary Systems
We present 82 photoelectric minima observations of 34 eclipsingbinaries.
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Book Review: The Light-Time Effect in Astrophysics: Causes and Cures of the O-C Diagram
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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.
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A catalogue of close binaries located in the δ Scuti region of the Cepheid instability strip
A catalogue of close eclipsing binary systems (detached andsemidetached) with at least one of the components located in the δScuti region of the Cepheid instability strip is presented. Thepositions of the stars in the instability strip are determined by theiraccurate temperatures and luminosities. Observationally detectedbinaries (20 semidetached, four detached and one unclassified) withoscillating components were included in the catalogue as a separatetable. The primaries of the oscillating Algols tend to be located nearthe blue edge of the instability strip. Using reliable luminosities andtemperatures determined by recent photometric and spectroscopic studies,we have found that at least one or two components of 71 detached and 90semidetached systems are located in the δ Scuti region of theCepheid instability strip. In addition, 36 detached or semidetachedsystems discovered by the Hipparcos satellite were also given as aseparate list. One of their components is seen in the δ Scutiregion, according to their spectral type or B - V colours. They arepotential candidate binaries with the δ Scuti-type pulsatingcomponents which need further photometric and spectroscopic studies inbetter precision. This catalogue covers information and literaturereferences for 25 known and 197 candidate binaries with pulsatingcomponents.
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The Algol System XX Cephei
We present new five-color photometric and spectroscopic observations ofthe Algol system XX Cephei (V=9.13, P=2.3 days). This system is known tohave a variable period. From analysis of both the period variations andthe light curve we found no support for apsidal motion. However, thereis a possible light-time effect. The period changes could also beepisodic. Our spectroscopic analysis yielded a classification of A4. Wefound no evidence of features attributable to the cooler component or ofactive mass transfer. Our photometric solution, using theWilson-Devinney modeling program, showed the system to be an Algolconfiguration with a mass ratio of 0.17. We determined the masses andradii, in solar units, to be M1=1.92, M2=0.33,R1=2.07, and R2=2.32, and the temperatures to beT1=8500 K and T2=4555 K. From the parallax givenin the Hipparcos catalog, neglecting reddening, absolute magnitudes ofMV=1.73 and 4.43 were determined for the primary andsecondary components, respectively.
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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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New Times of Minima of Some Eclipsing Binary Stars
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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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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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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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
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
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Minimum Times of Several Eclipsing Binaries
We present 26 minima times of 11 eclipsing binaries, observed between1996 and 1999.
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GSC 4288-186: a New Eccentric Binary
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The First Eclipsing Binary Observations at the Ulupinar Astrophysics Observatory
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Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
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New Times of Minima of Eclipsing Binary Systems
We present several photoelectric minima observations of 15 eclipsingbinaries.
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Minima of binary stars
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149 Bedeckungssterne der BAV-Programme. Eine Analyse der Beobachtungstatigkeit seit den Angangen.
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Bedeckungsveraenderliche mit Apsidendrehung.
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Das Brunner Punktesystem.
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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
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Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
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INHABITED SKY
