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First R and I Lights and Their Photometric Analyses of GSC 02393?00680
We obtained complete R and I light curves of GSC 02393?00680 in2008 and analyzed them with the 2003 version of the W-D code. It hasbeen shown that GSC 02393?00680 is a W-type shallow contact binarysystem with a high mass ratio, q = 1.600, and a degree of contactfactor, f = 5.0% (±1.3%). It will be a good example to check upon the TRO theory. A period investigation based on all available datasuggests that the system has a small-amplitude period oscillation(A3 = 0.0030d; T3 = 1.92 years). This may indicatethat it has a moderate-mass close third body, which is similar to XYLeo.
| Period Changes of DF Hydrae: Evidence of Mass Transfer and the Presence of a Cool Tertiary Companion
Combining our six new determined times of light minimum obtained from2001 to 2007 with others compiled from the literature, we investigatedthe period changes of DF Hydrae. The general trend of the O - C curvebased on all available data reveals that the period of the binary staris increasing continuously at a rate of dP/dt = + 1.11(±0.02)× 10-7dyr-1. After the long-term periodincrease was removed from the O - C diagram, it was discovered that theresiduals of the CCD and photoelectric observations suggest asmall-amplitude cyclic oscillation with a period of 21.5years. Thecontinuous period increase can be explained by mass transfer from thesecondary to the primary, indicating that DF Hydrae is on theTRO-controlled stage of the evolutionary scenario proposed by Qian. Thecyclic period variation suggests that DF Hydrae is a triple systemcontaining a cool tertiary component with a mass of M3sin i'= 0.21Modot in a 21.5-year orbit. By removing angularmomentum from the central binary system via Kozai oscillation or acombination of the Kozai cycle and tidal friction, the tertiarycompanion may play an important role for the formation and evolution ofthe contact system, which makes the eclipsing pair to have a shortinitial orbital period (i.e., P < 5d). In that case, thedetached progenitor of DF Hydrae evolves into the present contactconfiguration via a combination of magnetic braking and a case A masstransfer.
| Velocity-Curve Analysis of the Spectroscopic Binary Stars V373 Cas, V2388 Oph, V401 Cyg, GM Dra, V523 Cas, AB And and HD 141929 by Artificial Neural Networks
We used an Artificial Neural Network (ANN) to derive the orbitalparameters of spectroscopic binary stars. Using measured radial velocitydata of seven double-lined spectroscopic binary systems V373 Cas, V2388Oph, V401 Cyg, GM Dra, V523 Cas, AB And and HD 141929, we foundcorresponding orbital and spectroscopic elements. Our numerical resultsare in good agreement with those obtained by others using moretraditional methods.
| B.R.N.O. Times of minima
Not Available
| Angular momentum and mass evolution of contact binaries
Various scenarios of contact binary evolution have been proposed in thepast, giving hints of (sometimes contradictory) evolutionary sequencesconnecting A- and W-type systems. As the components of close detachedbinaries approach each other and contact binaries are formed, followingevolutionary paths transforms them into systems of two categories:A-type and W-type. The systems evolve in a similar way but underslightly different circumstances. The mass/energy transfer rate isdifferent, leading to quite different evolutionary results. Analternative scenario of evolution in contact is presented and discussed,based on the observational data of over one hundred low-temperaturecontact binaries. It results from the observed correlations amongcontact binary physical and orbital parameters. Theoretical tracks arecomputed assuming angular momentum loss from a system via stellar wind,accompanied by mass transfer from an advanced evolutionary secondary tothe main-sequence primary. A good agreement is seen between the tracksand the observed graphs. Independently of details of the evolution incontact and a relation between A- and W-type systems, the ultimate fateof contact binaries involves the coalescence of both components into asingle fast rotating star.
| 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.
| The evolutionary status of W Ursae Majoris-type systems
Well-determined physical parameters of 130 W Ursae Majoris (W UMa)systems were collected from the literature. Based on these data, theevolutionary status and dynamical evolution of W UMa systems areinvestigated. It is found that there is no evolutionary differencebetween W- and A-type systems in the M-J diagram, which is consistentwith the results derived from the analysis of observed spectral type andof M-R and M-L diagrams of W UMa systems. M-R and M-L diagrams of W- andA-type systems indicate that a large amount of energy should betransferred from the more massive to the less massive component, so thatthey are not in thermal equilibrium and undergo thermal relaxationoscillation. Moreover, the distribution of angular momentum, togetherwith the distribution of the mass ratio, suggests that the mass ratio ofthe observed W UMa systems decreases with decreasing total mass. Thiscould be the result of the dynamical evolution of W UMa systems, whichsuffer angular momentum loss and mass loss as a result of the magneticstellar wind. Consequently, the tidal instability forces these systemstowards lower q values and finally to rapidly rotating single stars.
| On the circulation luminosity in uniformly rotating stars
The equations governing meridional circulation in uniformly rotatingstars are discussed, allowing for turbulence and for baroclinic effects.Relations for barotropic stars with steady motions are generalized tobaroclinic stars with turbulence. The circulation luminosity (i.e., theluminosity carried by circulation through a level surface) is shown tobe zero in barotropic layers and positive in the bulk of a radiativeenvelope. The resulting effect is important in contact binaries.
| Contact Binaries with Additional Components. III. A Search Using Adaptive Optics
We present results of the Canada-France-Hawaii Telescope adaptive optics(AO) search for companions of a homogeneous group of contact binarystars, as a contribution to our attempts to prove the hypothesis thatthese binaries require a third star to become as close as observed. Inaddition to directly discovering companions at separations of>=1″, we introduced a new method of AO image analysis utilizingdistortions of the AO diffraction ring pattern at separations of0.07″-1″. Very close companions, with separations in thelatter range, were discovered in the systems HV Aqr, OO Aql, CK Boo, XYLeo, BE Scl, and RZ Tau. More distant companions were detected in V402Aur, AO Cam, and V2082 Cyg. Our results provide a contribution to themounting evidence that the presence of close companions is a very commonphenomenon for very close binaries with orbital periods <1 day.Based on observations obtained at the Canada-France-Hawaii Telescope,which is operated by the National Research Council of Canada, theInstitut National des Sciences de l'Univers of the Centre National de laRecherche Scientifique of France, and the University of Hawaii.
| B.R.N.O. Contributions #34
Not Available
| New Minima Times of Selected Eclipsing Binaries
We present 169 CCD and photoelectric times of minima of selectedeclipsing binaries obtained from 2005 to 2007 at observatories inSlovakia
| Formation and Evolution of W Ursae Majoris Contact Binaries
The origin and evolution of W UMa systems are discussed based on All SkyAutomated Survey (ASAS) data and the mean kinematic ages of foursubgroups of 97 field contact binaries (FCBs). The period distributionof eclipsing binaries discovered by ASAS suggests that a period limit totidal locking for the close binaries is about 2.24 days, so that most WUMa systems might be formed from detached binaries with periodsP<~2.24 days, and a maximum advanced time from a detached system to aW UMa is about 3.23 Gyr. Moreover, the secular evolution of the angularmomentum (AM), the system mass, and the orbital period of 97 FCBs wereinvestigated according to the mean kinematic ages, which were setaccording to AM bins. AMs, systemic masses, and orbital periods wereshown to be decreasing with kinematic age. Their first-order decreasingrates have been determined as J˙/J=1.86×10-10yr-1, M˙/M=0.95×10-10 yr-1,and P˙/P=1.24×10-10 yr-1, and theaverage amplification (A¯=dlnJ/dlnM) is derived to be 1.96. Theseare lower than those derived from detached chromospherically activebinaries (CABs). This suggests that the magnetic activity level of FCBsis indeed weaker than that of CABs. Meanwhile, the decreasing rate of AMof FCBs is found to be equal to an average value in a cycle of a cyclicmodel of contact binaries. This might suggest that the evolution of FCBsundergoes thermal relaxation oscillation (TRO) and that the coalescenceof W UMa systems is a very long process, which is also indicated by thedynamical evolution of FCBs.
| Physical parameters and multiplicity of five southern close eclipsing binaries
Aims.We detected tertiary components of close binaries from spectroscopyand light curve modelling, investigated the light-travel time effect andthe possibility of magnetic activity cycles, measured mass ratios forunstudied systems, and derived absolute parameters. Methods: We carriedout new photometric and spectroscopic observations of five bright (< 10.5 mag) close eclipsing binaries, predominantly in thesouthern skies. We obtained full Johnson BV light curves, which weremodelled with the Wilson-Devinney code. Radial velocities were measuredwith the cross-correlation method using IAU radial velocity standards asspectral templates. Period changes were studied with the O-C method,utilising published epochs of minimum light (XY Leo) and ASAS photometry(VZ Lib). Results: For three objects (DX Tuc, QY Hya, V870 Ara),absolute parameters have been determined for the first time. Wespectroscopically detected the tertiary components in XY Leo and VZ Liband discovered one in QY Hya. For XY Leo we updated the light-timeeffect parameters and detected a secondary periodicity of about 5100 din the O-C diagram that may hint at the existence of short-periodmagnetic cycles. A combination of recent photometric data shows that theorbital period of the tertiary star in VZ Lib is likely to be over 1500d. QY Hya is a semi-detached X-ray active binary in a triple system withK and M-type components, while V870 Ara is a contact binary with thethird smallest spectroscopic mass ratio for a W UMa star to date (q =0.082 ± 0.030). Being close to the theoretical minimum forcontact binaries, this small mass ratio suggests that V870 Ara has thepotential of constraining evolutionary scenarios of binary mergers. Theinferred distances to these systems are compatible with the Hipparcosparallaxes.Based on observations made at the Siding Spring Observatory, Australia.Light curves and radial velocity data are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/943
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 119 minima times of 47 eclipsing binaries.
| New Times of Minima of Eclipsing Binary Systems
We present 82 photoelectric minima observations of 34 eclipsingbinaries.
| New Times of Minima of Some Eclipsing Binary Stars
Not Available
| Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation
Orbital angular momentum (OAM, Jo), systemic mass (M) andorbital period (P) distributions of chromospherically active binaries(CAB) and W Ursae Majoris (W UMa) systems were investigated. Thediagrams of and logJo-logM were formed from 119 CAB and 102 WUMa stars. The logJo-logM diagram is found to be mostmeaningful in demonstrating dynamical evolution of binary star orbits. Aslightly curved borderline (contact border) separating the detached andthe contact systems was discovered on the logJo-logM diagram.Since the orbital size (a) and period (P) of binaries are determined bytheir current Jo, M and mass ratio, q, the rates of OAM loss(dlogJo/dt) and mass loss (dlogM/dt) are primary parametersto determine the direction and the speed of the dynamical evolution. Adetached system becomes a contact system if its own dynamical evolutionenables it to pass the contact border on the logJo-logMdiagram. The evolution of q for a mass-losing detached system is unknownunless the mass-loss rate for each component is known. Assuming q isconstant in the first approximation and using the mean decreasing ratesof Jo and M from the kinematical ages of CAB stars, it hasbeen predicted that 11, 23 and 39 per cent of current CAB stars wouldtransform to W UMa systems if their nuclear evolution permits them tolive 2, 4 and 6 Gyr, respectively.
| 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.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Contact Binaries with Additional Components. II. A Spectroscopic Search for Faint Tertiaries
It is unclear how very close binary stars form, given that during thepre-main-sequence phase the component stars would have been inside eachother. One hypothesis is that they formed farther apart but were broughtin closer after formation by gravitational interaction with a thirdmember of the system. If so, all close binaries should be members oftriple (or higher order) systems. As a test of this prediction, wepresent a search for the signature of third components in archivalspectra of close binaries. In our sample of 75 objects, 23 show evidencefor the presence of a third component, down to a detection limit oftertiary flux contributions of about 0.8% at 5200 Å (consideringonly contact and semidetached binaries, we find 20 out of 66). In ahomogeneous subset of 59 contact binaries, we are fairly confident thatthe 15 tertiaries we have detected are all tertiaries present with massratios 0.28<~M3/M12<~0.75 and implied outerperiods P<~106 days. We find that if the frequency oftertiaries were the same as that of binary companions to solar-typestars, one would expect to detect about 12 tertiaries. In contrast, ifall contact binaries were in triple systems, one would expect about 20.Thus, our results are not conclusive but are sufficiently suggestive towarrant further studies.
| Variation in the orbital period of W UMa-type contact systems
The secular variation in the orbital period Porb is studiedas a function of the mass ratio q of the components in a sample of 73contact systems of class W UMa constructed from a survey of current(1991–2003) published photometric and spectroscopic data. Almostall the W UMa-systems (>93% of this sample) are found to have avariation in their orbital periods Porb which alternates insign independently of their division into A-and Wsubclasses. Astatistical study of this sample in terms of the observedcharacteristics dPorb/dt and q showed that on the average thenumbers of increases (35 systems) and decreases (33 systems) in theperiods are the same, which indicates the existence of flows directedalternately from one component to the other and illustrates the cyclicalcharacter of the thermal oscillations. An analysis of the behavior ofdPorb/dt as a function of the mass interval of the primarycomponent yields a more accurate value for the mass ratio, q ≈ 0.4÷ 0.45 at which contact binaries are separated into A-andW-subclasses. No correlations were observed between the fill-out factorfor the outer contact configuration, the total mass of the contactsystem, and the mass ratio of the components, on one hand, and the signof the secular variation in the period. The physical properties andevolutionary features of these systems are discussed.
| Contact Binaries with Additional Components. I. The Extant Data
We have attempted to establish observational evidence for the presenceof distant companions that may have acquired and/or absorbed angularmomentum during the evolution of multiple systems, thus facilitating orenabling the formation of contact binaries. In this preliminaryinvestigation we use several techniques (some of themdistance-independent) and mostly disregard the detection biases ofindividual techniques in an attempt to establish a lower limit to thefrequency of triple systems. While the whole sample of 151 contactbinary stars brighter than Vmax=10 mag gives a firm lowerlimit of 42%+/-5%, the corresponding number for the much better observednorthern-sky subsample is 59%+/-8%. These estimates indicate that mostcontact binary stars exist in multiple systems.
| 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.
| An Orbital Period Study of the W UMa-Type Binary RZ Comae Berenicis
New photoelectric and CCD photometry observations of a short-period WUMa-type binary system, RZ Com, are presented. The light curves ofBroglia (1960, Contr. Milano-Merate, 165) were symmetric in V band,while the present light curve shows a typical O'Connell effect, withMaximum I brighter than Maximum II by 0.015mag. It is found that thelight curve of the binary star has changed from W-subtype to A-subtypeaccording to Binnendijk's classification. This variation may be causedby the activity of dark spot on the primary component. Combining fournewly determined times of the light minimum with others published in theliterature, the orbital period change of the system was investigated. Asmall-amplitude oscillation (A = 0.0058 d), with a period of 44.8yr hasbeen discovered to be superimposed on a long-term period increase with arate of dP/dt = +4.12 × 10-8 d yr-1. Theperiod oscillation can be explained either by the light-time effect viathe presence of an unseen third body or by magnetic-activity cycles ofthe components. The mass ratio of RZ Com is q = 0.43. The secular periodvariation is in agreement with the conclusions of Qian (2001, MNRAS,328, 914; 2003, MNRAS, 342, 1260). This indicates that it is on theTRO-controlled stage of the evolutionary scheme proposed by Qian.
| New Minima of Selected Eclipsing Close Binaries
We present 180 CCD and photoelectric times of minima of selected closeeclipsing binaries.
| Indirect evidence for short period magnetic cycles in W UMa stars. Period analysis of five overcontact systems.
Complex period variations of five W UMa type binaries (ABAnd, OO Aql, DK Cyg,V566 Oph, U Peg) were investigatedby analyzing their O-C diagrams, and several common features were found.Four of the five systems show secular period variations at a constantrate on the order of |dot{P}sec/P|10-7yr-1. In the case of AB And, OOAql, and U Peg a high-amplitude, nearlyone-century long quasi-sinusoidal pattern was also found. It might beexplained as light-time effect, or by some magnetic phenomena, althoughthe mathematical, and consequently the physical, parameters of thesefits are very problematic, as the obtained periods are very close to thelength of the total data range. The most interesting feature of thestudied O-C diagrams is a low amplitude ( 2-4×10-3 d)modulation with a period around 18-20 yr in four of the five cases. Thisphenomenon might be indirect evidence of some magnetic cycle inlate-type overcontact binaries as an analog to the observed activitycycles in RS CVn systems.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| CCD Observations of Times of Minima of Eclipsing Binaries
120 minima timings are reported for 39 E. B. systems observed from 2002to 2005 with the Rigel telescope at Winer Observatory. The timings weredetermined using a folded light curve analysis of light curves derivedfrom CCD images. Typical timing uncertainties were 30-60 sec.
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