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Physical parameters of components in close binary systems - VII
We present results of the modelling of multicolour light curves of 10contact binary systems: V376And, V523Cas, CCCom, BXDra, FGHya, UZLeo,XYLeo, AMLeo, EXLeo and RTLMi. The solutions resulted in a contactconfiguration for all systems. We found only FGHya and UZLeo to be indeep contact, the latter almost filling the outer critical lobe. Theabsolute parameters of the components have been determined with anaccuracy of about a few per cent based on combined photometric andradial velocity curves, enlarging the sample of systems to 58 for whichthe physical parameters have been obtained in a uniform way. All butthree systems (BXDra, AMLeo and RTLMi) show asymmetries andpeculiarities in the observed light curves, interpreted as resultingfrom their magnetic activity.
| A Multicolour Photometric Study for the W Ursae Majoris Type Binary LR Camelopardalis
A CCD multicolour photometry for the eclipsing binary LR Camelopardalis,obtained on 2008 December 19 and 2010 January 29 and 30 at the XinglongStation of NAOC, is presented. Using the Wilson-Devinney binary code, aphotometric solution was simultaneously derived from BVR light curves.The results show that LR Cam belongs to a W-type contact binary, with amass ratio of q = 0.300(1) and an overcontact degree of f = 23.5(5)%,indicating that LR Cam is a weak-contact binary. The asymmetric lightcurves (i.e., the O'Connell effect) were modeled by a dark spot on themore massive component. From the (O - C) curve of LR Cam, it is foundthat the orbital period shows a sine-like variation superimposed on asecular period increase. The quasi-sinusoidal variation, with A =0.d0039(1), P3 = 5.34(2) yr, and e' = 0.56(3), maymore likely result from a light-time effect via the presence of a thirdbody. The long-term period increases at a rate of dP/dt = +0.65(9)× 10-7 d yr-1, which may be interpreted bymass transfer from the less-massive component to the more-massive one.With mass transferring, LR Cam may evolve into a broken-contact binary.
| 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.
| Photometric Study of the Very Short Period Shallow Contact Binary DD Comae Berenices
The first photometric solutions of the very short period (VSP) closebinary DD Comae Berenices (P = 0fd26920811) based on our new complete(IR)C light curves are derived by the 2003 version Wilson-VanHamme code. They show that the system belongs to shallow contact W-typeW UMa systems with a degree of overcontact of 8.7%. The observed lightcurve distortions are explained by employing the spots model due to thelate-type nature of both components. We have collected all availablephotometric data about the system with emphasis on the individualobservational data, which we treated simultaneously using our own methodbased on the usage of computed model light curves as templates. Werecalculated published times of light minimum and added new ones of ourown to construct an O - C diagram that spans over 70 years. Using aleast squares method orthogonal quadratic model function, we found thatthe orbital period of DD Com is continuously increasing with\dot{P}=0.00401(22) s yr-1. The period increase may be causedby the mass transfer from the less-massive component to the more-massiveone. With the period increase, the binary is evolving from the presentshallow contact phase to the broken stage predicted by the thermalrelaxation oscillation (TRO) theory. Compared with other VSP systems, DDCom is a rare system that lies on the expanding phase of the TRO cycle.Until now, only four such systems including DD Com are found in thisstage. Thus, this target is another good observational proof of the TROtheory in a very short period region.
| 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.
| A list of minima and maxima timings
The list contains minima of eclipsing and maxima of pulsating stars, itcontinues the list published in OEJV 0073.
| XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources
The 18,806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-raysources are quantitatively cross-associated with near-infrared (NIR)sources from the Two Micron All Sky Survey Point Source Catalog(2MASS/PSC). An association catalog is presented, listing the mostlikely counterpart for each RASS/BSC source, the probability Pid that the NIR source and X-ray source are uniquelyassociated, and the probability P no-id that none of the2MASS/PSC sources are associated with the X-ray source. The catalogincludes 3853 high quality (P id>0.98) X-ray-NIR matches,2280 medium quality (0.98 >= P id>0.9) matches, and4153 low quality (0.9 >= P id>0.5) matches. Of the highquality matches, 1418 are associations that are not listed in the SIMBADdatabase, and for which no high quality match with a USNO-A2 opticalsource was presented for the RASS/BSC source in previous work. Thepresent work offers a significant number of new associations withRASS/BSC objects that will require optical/NIR spectroscopy forclassification. For example, of the 6133 P id>0.92MASS/PSC counterparts presented in the association catalog, 2411 haveno classification listed in the SIMBAD database. These 2MASS/PSC sourceswill likely include scientifically useful examples of known sourceclasses of X-ray emitters (white dwarfs, coronally active stars, activegalactic nuclei), but may also contain previously unknown sourceclasses. It is determined that all coronally active stars in theRASS/BSC should have a counterpart in the 2MASS/PSC, and that the uniqueassociation of these RASS/BSC sources with their NIR counterparts thusis confusion limited.
| The chromospherically active binary CFTuc revisited
This paper presents results derived from analysis of new spectroscopicand photometric observations of the chromospherically active binarysystem CFTuc. New high-resolution spectra, taken at the Mt. JohnUniversity Observatory in 2007, were analysed using two methods:cross-correlation and Fourier-based disentangling. As a result, newradial velocity curves of both components were obtained. The resultingorbital elements of CFTuc are a1 sini = 0.0254 +/- 0.0001au,a2sini = 0.0228 +/- 0.0001au, M1sini = 0.902 +/-0.005Msolar and M2sini = 1.008 +/-0.006Msolar. The cooler component of the system showsH? and CaII H&K emissions. Using simultaneous spectroscopicand photometric observations, an anticorrelation between the H?emission and the BV light curve maculation effects was found. Thisbehaviour indicates a close spatial association between photospheric andchromospheric active regions. Our spectroscopic data and recent BV lightcurves were solved simultaneously using the Wilson-Devinney code. A darkspot on the surface of the cooler component was assumed to explain largeasymmetries observed in the light curves. The following absoluteparameters of the components were determined: M1 = 1.11 +/-0.01Msolar, M2 = 1.23 +/- 0.01Msolar,R1 = 1.63 +/- 0.02Rsolar, R2 = 3.60 +/-0.02Rsolar, L1 = 3.32 +/- 0.51Lsolarand L2 = 3.91 +/- 0.84Lsolar. The primarycomponent has an age of about 5Gyr and is approaching its main-sequenceterminal age. The distance to CFTuc was calculated to be 89 +/- 6pc fromthe dynamic parallax, neglecting interstellar absorption, in agreementwith the Hipparcos value. The orbital period of the system was studiedusing the O-C analysis. The O-C diagram could be interpreted in terms ofeither two abrupt changes or a quasi-sinusoidal form superimposed on adownward parabola. These variations are discussed by reference to thecombined effect of mass transfer and mass loss, the Applegate mechanismand also a light-time effect due to the existence of a third body in thesystem.
| Close binary and other variable stars in the solar-age Galactic open cluster M 67
We present multi-colour time-series CCD photometry of the solar-agegalactic open cluster M 67 (NGC 2682). About 3600 frames spread over 28nights were obtained with the 1.5 m Russian-Turkish and 1.2 m Mercatortelescopes. High-precision observations of the close binary stars AHCnc, EV Cnc, ES Cnc, the ? Scuti type systems EX Cnc and EW Cnc,and some long-period variables belonging to M 67 are presented. Threefull multi-colour light curves of the overcontact binary AH Cnc wereobtained during three observing seasons. Likewise we gathered threelight curves of EV Cnc, an EB-type binary, and two light curves of ESCnc, a blue straggler binary. Parts of the light change of long-termvariables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained.Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done usingall times of mid-eclipse available in the literature and those obtainedin this study. In addition, we analyzed multi-colour light curves of theclose binaries and also determined new frequencies for the ? Scutisystems. The physical parameters of the close binary stars weredetermined with simultaneous solutions of multi-colour light and radialvelocity curves. Finally we determined the distance of M 67 as 857(33)pc via binary star parameters, which is consistent with an independentmethod from earlier studies.Based on observations made with the Mercator Telescope, operated on theisland of La Palma by the Flemish Community, at the Spanish Observatoriodel Roque de los Muchachos of the Instituto de Astrofísica deCanarias and TÜB?TAK National Observatory Russian-Turkishtelescope operated at Sakl?kent, Antalya.
| An Orbital Period Investigation of the Solar-Type Overcontact Binary V700 Cygni
Not Available
| B.R.N.O. Contributions #36, Times of minima
Not Available
| Radial Velocity Studies of Close Binary Stars. XV
Radial velocity (RV) measurements and sine curve fits to the orbital RVvariations are presented for the last eight close binary systemsanalyzed in the same way as in the previous papers of this series: QXAnd, DY Cet, MR Del, HI Dra, DD Mon, V868 Mon, ER Ori, and Y Sex. Foranother seven systems (TT Cet, AA Cet, CW Lyn, V563 Lyr, CW Sge, LV Vir,and MW Vir), phase coverage is insufficient to provide reliable orbitsbut RVs of individual components were measured. Observations of a fewcomplicated systems observed throughout the David Dunlap Observatory(DDO) close binary program are also presented; among them is anespecially interesting multiple system V857 Her which—in additionto the contact binary—very probably contains one or more subdwarfcomponents of much earlier spectral type. All suspected binaries whichwere found to be most probably pulsating stars are briefly discussed interms of mean RVs and projected rotation velocities (vsin i) as well asspectral-type estimates. In two of them, CU CVn and V752 Mon, thebroadening functions show a clear presence of nonradial pulsations. Thepreviously missing spectral types for Paper I are given here in additionto such estimates for most of the program stars of this paper.Based on the data obtained at the David Dunlap Observatory, Universityof Toronto, Toronto, Canada.
| BAV-Results of observations - Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| New absolute magnitude calibrations for W Ursa Majoris type binaries
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed.31 W UMa stars, which have the most accurate parallaxes(σπ/π<0.15) which are neither associated with aphotometric tertiary nor with evidence of a visual companion, wereselected for re-calibrating the Period-Luminosity-Color (PLC) relationof W UMa stars. Using the Lutz-Kelker (LK) bias corrected (mostprobable) parallaxes, periods ({0.26< P< 0.87}, P in days), andcolors ({0.04<(B-V)0<1.28}) of the 31 selected W UMa,the PLC relation have been revised and re-calibrated. The differencebetween the old (revised but not bias corrected) and the new (LK biascorrected) relations are almost negligible in predicting the distancesof W UMa stars up to about 100 pc. But, it increases and may becomeintolerable as distances of stars increase. Additionally, using(J-H)0 and (H-K_s)0 colors from 2MASS (Two MicronAll Sky Survey) data, a PLC relation working with infrared data wasderived. It can be used with infrared colors in the range-0.01<(J-H)0<0.58, and{-0.10<(H-K_s)0<0.18}. Despite of the fact that the2MASS data refer to single epoch observations which are not guaranteedto be taken at maximum brightness of the W UMa stars, the establishedrelation has been found surprisingly consistent and reliable inpredicting LK corrected distances of W UMa stars.
| Coronal Activity from the ASAS Eclipsing Binaries
We combine the catalog of eclipsing binaries from the All Sky AutomatedSurvey (ASAS) with the ROSAT All Sky Survey (RASS). The combinationresults in 836 eclipsing binaries that display coronal activity and isthe largest sample of active binary stars assembled to date. By usingthe (V-I) colors of the ASAS eclipsing binary catalog, we are able todetermine the distances and thus bolometric luminosities for themajority of eclipsing binaries that display significant stellaractivity. A typical value for the ratio of soft X-ray to bolometricluminosity is LX/Lbol? a few×10-4, similar to the ratio of soft X-ray to bolometricflux FX/Fbol in the most active regions of theSun. Unlike rapidly rotating isolated late-type dwarfs - stars withsignificant outer convection zones - a tight correlation between Rossbynumber and activity of eclipsing binaries is absent. We find evidencefor the saturation effect and marginal evidence for the so-called``super-saturation'' phenomena. Our work shows that wide-field stellarvariability searches can produce a high yield of binary stars withstrong coronal activity.The combined ASAS and RASS catalog, as well as the results of this workare available for download.
| 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.
| A catalogue of chromospherically active binary stars (third edition)
The catalogue of chromospherically active binaries (CABs) has beenrevised and updated. With 203 new identifications, the number of CABstars is increased to 409. The catalogue is available in electronicformat where each system has a number of lines (suborders) with a uniqueorder number. The columns contain data of limited numbers of selectedcross references, comments to explain peculiarities and the position ofthe binarity in case it belongs to a multiple system, classicalidentifications (RS Canum Venaticorum, BY Draconis), brightness andcolours, photometric and spectroscopic data, a description of emissionfeatures (CaII H and K, Hα, ultraviolet, infrared),X-ray luminosity, radio flux, physical quantities and orbitalinformation, where each basic entry is referenced so users can go to theoriginal sources.
| 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.
| BD -22 5866: A Low-Mass, Quadruple-lined Spectroscopic and Eclipsing Binary
We report our discovery of an extremely rare, low-mass, quadruple-linedspectroscopic binary BD -22 5866 (=NLTT 53279, integrated spectral type= M0 V), found during an ongoing search for the youngest M dwarfs in thesolar neighborhood. From the cross-correlation function, we are able tomeasure relative flux levels, estimate the spectral types of thecomponents, and set upper limits on the orbital periods and separations.The resulting system is hierarchical, composed of a K7 + K7 binary andan M1 + M2 binary with semimajor axes ofaAsiniA<=0.06 andaBsiniB<=0.30 AU. A subsequent search of theSuperWASP photometric database revealed that the K7 + K7 binary iseclipsing with a period of 2.21 days and at an inclination angle of85°. Within uncertainties of 5%, the masses and radii of bothcomponents appear to be equal (0.59 Msolar, 0.61Rsolar). These two tightly orbiting stars (a=0.035 AU) are insynchronous rotation, causing the observed excess Ca II, Hα,X-ray, and UV emission. The fact that the system was unresolved withpublished adaptive optics imaging, limits the projected physicalseparation of the two binaries at the time of the observation todAB<~4.1 AU at the photometric distance of 51 pc. Themaximum observed radial velocity difference between the A and B binarieslimits the orbit to aABsiniAB<=6.1 AU. As thistight configuration is difficult to reproduce with current formationmodels of multiple systems, we speculate that an early dynamical processreduced the size of the system, such as the interaction of the twobinaries with a circumquadruple disk. Intensive photometric,spectroscopic, and interferometric monitoring, as well as a parallaxmeasurement of this rare quadruple system, is certainly warranted.Based on observations collected at the W. M. Keck Observatory and theCanada-France-Hawaii Telescope (CFHT). The Keck Observatory is operatedas a scientific partnership between the California Institute ofTechnology, the University of California, and NASA, and was madepossible by the generous financial support of the W. M. Keck Foundation.The CFHT is operated by the National Research Council of Canada, theCentre National de la Recherche Scientifique of France, and theUniversity of Hawaii.
| AD Cancri: A Shallow Contact Solar-Type Eclipsing Binary and Evidence for a Dwarf Third Component and a 16 Year Magnetic Cycle
CCD photometric observations of AD Cancri obtained from 2000 March 7 to2004 December 20 are presented. Variations of the light levels at theprimary minimum and both maxima are found. Uniform solutions of foursets of photometric data were derived by using the Wilson-Devinneymethod. The solutions suggest that AD Cancri is a shallow W-type contactbinary (f=8.3%+/-1.3%) with a high mass ratio of 1/q=0.770+/-0.002. Thelong-term variation of the light curve is explained by variabledark-spot models of the more massive component star with a possible 17yr cycle. Our 13 times of light minimum over 5 years, including otherscollected from the literature, have been used for the period study. Thecomplex period changes can be sorted into a long-term period increase atrate of dP/dt=+(4.94+/-0.16)×10-7 days yr-1,a 16.2 yr periodic component (A3=0.0155 days), and a verysmall amplitude period oscillation (A4=0.0051 days,P4=6.6 yr). The existence of third light may indicate thatthere is a tertiary component in the binary system. Solving thefour-band light curves of Samec & Bookmyer, it is found that thecontribution of the tertiary component to the total light of the triplesystem increases with wavelength, which suggests that it is very cooland may be a very red main-sequence star. The small-amplitude periodoscillation may be caused by the light-time effect of the cool tertiarycomponent (M3~0.41 Msolar). The 16.2 yr periodiccomponent in the orbital period and the 17 yr cyclic activity of thedark spot on the more massive component both may reveal that the moremassive component displays solar-type magnetic activity with a cyclelength of about 16 yr.
| 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.
| A Mechanism for Orbital Period Modulation and Irregular Orbital Period Variations in Close Binaries
Orbital period modulation is observed in many magnetically active closebinaries. It can be explained by magnetic connection between two stars.Magnetic connection produces weak force between the two stars. As themagnetic field varies periodically, the orbital period also showscyclical variations. The mechanism can also be used to explain irregularorbital period variations and orbital period jumps. The mean surfacemagnetic strength is calculated by using the Radia package, which isdedicated to 3D magnetostatics computation. On the basis of the results,a practical equation is given to calculate surface magnetic strength.
| Ternarity, Activity, and Evolutionary State of the W UMa-Type Binary UX Eridani
Charge-coupled device photometric observations of the W UMa-type binarystar UX Eridani are presented. Comparing the B light curve with thatobtained by Binnendijk in 1964-1965, the variation of the light curvearound the primary minimum was found. Photometric solutions ofBinnendijk's and our light curves were derived by using the new versionof the Wilson-Devinney program. Our solutions confirmed that UX Eri is amarginal W-type overcontact binary system with a very low degree ofovercontact, f < 15%. The change of the light curve around theprimary minimum was explained as the disappearance of a dark spot on themore massive component star. This suggests that UX Eri shows strongmagnetic activity, which is in agreement with its having the highestX-ray flux among 57 W UMa-type binary stars studied by Stepien et al.The high level of magnetic activity was interpreted as the result of ashallow common convective envelope. Orbital period changes were analyzedusing several newly determined CCD times of light minimum together withothers collected from the literature. A cyclic period change (T = 45.3yr) was found to be superimposed on a long-term increase (dP/dt = +7.7× 10-8 days yr-1). The period oscillationand the existence of third light both confirm that UX Eri contains atertiary component. Since no spectroscopic companion was found, it isestimated that the mass of the third body is M3 < 0.56Modot. The tertiary component star is moving in an eccentricorbit (e' = 0.72) with an orbital inclination of i' > 44.5°. Thetertiary component may have played an important role in the formation ofthe progenitor of UX Eri by transferring angular momentum during theKozai oscillation. In that way, the detached progenitor could evolveinto overcontact configuration via magnetic braking. It was found thatthe timescale of the period increase is close to the thermal timescaleof the less massive component, which suggests that UX Eri is in anevolutionary state of thermally conservative mass transfer from the lessmassive component to the more massive one.
| B.R.N.O. Contributions #34
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Minima of Some Eclipsing Binary Stars
We present 51 minima times of 19 eclipsing binaries.
| Absolute Properties of the Binary System BB Pegasi
We present ground-based photometry of the low-temperature contact binaryBB Peg. We collected all the times of mid-eclipse available in theliterature and combined them with those obtained in this study. Analysesof the data indicate a period increase of(3.0+/-0.1)×10-8 days yr-1. This periodincrease of BB Peg can be interpreted in terms of the mass transfer2.4×10-8 Msolar yr-1 from theless massive to the more massive component. The physical parameters havebeen determined as Mc=1.42 Msolar,Mh=0.53 Msolar, Rc=1.29Rsolar, Rh=0.83 Rsolar,Lc=1.86 Lsolar, and Lh=0.94Lsolar through simultaneous solutions of light and of theradial velocity curves. The orbital parameters of the third body, whichorbits the contact system in an eccentric orbit, were obtained from theperiod variation analysis. The system is compared to the similarbinaries in the Hertzsprung-Russell and mass-radius diagrams.
| 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
| Cross-Correlation in Four Dimensions: Application to the Quadruple-lined Spectroscopic System HD 110555
We develop a technique to measure radial velocities of stars fromspectra that present four sets of lines. The algorithm is an extensionof the two-dimensional cross-correlation method TODCOR to fourdimensions. It computes the correlation of the observed spectrum againsta combination of four templates with all possible shifts, and it alsoallows for the derivation of the light ratios of the components. Aftertesting the algorithm and demonstrating its ability to measure Dopplershifts accurately even under conditions of heavy line blending, we applyit to the case of the quadruple-lined system HD 110555. The primary andsecondary components of this previously known visual binary(ρ~0.4'') are each shown to be double-lined spectroscopicbinaries with periods of 57 days and 76 days, respectively, making thesystem a hierarchical quadruple. The secondary in the 76 day subsystemcontributes only 2.5% to the total light, illustrating the ability ofthe method to measure velocities of very faint components.
| Radial Velocity Studies of Close Binary Stars. XII.
Radial velocity measurements and sine-curve fits to the orbital radialvelocity variations are presented for 10 close binary systems: OO Aql,CC Com, V345 Gem, XY Leo, AM Leo, V1010 Oph, V2612 Oph, XX Sex, W UMa,and XY UMa. Most of these binaries have been observed spectroscopicallybefore, but our data are of higher quality and consistency than in theprevious studies. While most of the studied eclipsing pairs are contactbinaries, V1010 Oph is probably a detached or semidetached double-linedbinary, and XY UMa is a detached, chromospherically active system whosebroadening functions clearly show well-defined and localized dark spotson the primary component. A particularly interesting case is XY Leo,which is a member of visually unresolved quadruple system composed of acontact binary and a detached, noneclipsing, active binary with an 0.805day orbital period. V345 Gem and AM Leo are known members of visualbinaries. We found faint visual companions at about 2"-3" from XX Sexand XY UMa.Based on data obtained at the David Dunlap Observatory, University ofToronto.
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