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BL Andromedae and GW Tauri: close binary stars in a key evolutionary stage
A photoelectric light curve of BL And is presented along with the firstCCD light curve of GW Tau. Both objects are short-period eclipsingbinaries and were observed in 2003 or 2004. Photometric elements werecomputed using the latest version of the Wilson-Van Hamme code. Theresults reveal that BL And is a semidetached system with the primarycomponent filling its Roche lobe and the secondary one almost fillingbut still detached, while GW Tau is a marginal-contact binary systemwith a small degree of contact (f= 10.9 per cent) and a largetemperature difference of about 3100K. All available eclipse times,including new ones, were analysed for each system. It was found that theorbital period of BL And is decreasing at the rate of dP/dt=-2.36× 10-8 (+/-0.09)dyr-1 while that of GW Taumay be decreasing or oscillating. We think period decrease is moreprobable. The derived configuration and secular period decrease for BLAnd combined with the asymmetry of the light curve indicate that thissystem may evolve from the present semidetached phase into a contactstage, with mass transfer from the primary component to the secondaryone through the L1 point, or that it might just undergo thebroken stage predicted by the theory of thermal relaxation oscillations.In contrast, GW Tau is a marginal-contact binary in poor thermal contactand may be at the beginning of the contact phase.
| 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.
| Observed Orbital Eccentricities
For 391 spectroscopic and visual binaries with known orbital elementsand having B0-F0 IV or V primaries, we collected the derivedeccentricities. As has been found by others, those binaries with periodsof a few days have been circularized. However, those with periods up toabout 1000 or more days show reduced eccentricities that asymptoticallyapproach a mean value of 0.5 for the longest periods. For those binarieswith periods greater than 1000 days their distribution of eccentricitiesis flat from 0 to nearly 1, indicating that in the formation of binariesthere is no preferential eccentricity. The binaries with intermediateperiods (10-100 days) lack highly eccentric orbits.
| A near-contact binary: CN Andromedae
New BVR light curves and photometric analysis of the eclipsing binarystar CN And are presented. The shape of the light curves are typical ofβ Lyr type, and there are large asymmetries between maxima. The BVRlight curves and the radial velocity curves (from Rucinski et al. 2000)were solved with the Wilson-Devinney method, simultaneously. The resultssuggest that CN And is a almost contact binary system, in which thecomponent stars are filling 99% of their Roche lobes. We discussthe model with a large dark starspot on the more massive star and abright substellar spot on the companion to account for the light curveasymmetries. The absolute parameters of the system were also derived.The system resembles the near contact binary V1010 Oph according to itsRoche configuration and light curve asymmetries. We, also, discuss theevolution of the system: it seems to be in a transition phase to thecontact era. All previous times of minimum light were collected andcombined with the new ones presented in this work. The variation of theorbital period of the system was then analyzed. The results reveal thatthe orbital period has a secular decrease of about 1.98±0.04 secper century, which corresponds to a conservative mass transfer from themore to the less massive component at a rate of(1.52±0.09)×10-7m_ȯ/yr or a mass loss fromthe primary component due to magnetic stellar winds at a rate of(7.83±0.09)×10-8m_ȯ/yr.
| Photometric Studies of the Near-Contact Binary AX Draconis
We have obtained CCD photometric observations of the near-contact binaryAX Dra during two observing seasons from 2001 March through May and from2003 April and May. From these measurements, the seasonal light curvesof AX Dra for 2001 and 2003 were compiled, and a total of 13 new timingsof minimum light were calculated. An analysis of the resulting O-Cdiagram reveals evidence for a periodic change with a semiamplitude of0.0061 days and a period of 56.1 yr, but this conclusion dependsentirely on the photographic plate estimates around 1960. Our lightcurves display the conventional O'Connell effect and small-scaleyear-to-year light variability. If these light variations are producedby a stellar spot, a cool-model spot on the secondary star satisfiesboth seasonal light curves quite well. The same representation appliesto the only other published photoelectric light curves.
| 163. List of Minima Timings of Eclipsing Binaries by BBSAG Observers
Not Available
| The Solar Type Near Contact Binary, CR Canis Majoris
Not Available
| UBVRI CCD Observations of HM Monocerotis and Sixty Two Year Period Study
Not Available
| Tidal Effects in Binaries of Various Periods
We found in the published literature the rotational velocities for 162B0-B9.5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity classes V orIV, that are in spectroscopic or visual binaries with known orbitalelements. The data show that stars in binaries with periods of less thanabout 4 days have synchronized rotational and orbital motions. Stars inbinaries with periods of more than about 500 days have the samerotational velocities as single stars. However, the primaries inbinaries with periods of between 4 and 500 days have substantiallysmaller rotational velocities than single stars, implying that they havelost one-third to two-thirds of their angular momentum, presumablybecause of tidal interactions. The angular momentum losses increase withdecreasing binary separations or periods and increase with increasingage or decreasing mass.
| On the properties of contact binary stars
We have compiled a catalogue of light curve solutions of contact binarystars. It contains the results of 159 light curve solutions. Theproperties of contact binary stars were studied using the cataloguedata. As is well known since Lucy's (\cite{Lucy68a},b) and Mochnacki's(\cite{Mochnacki81}) studies, primary components transfer their ownenergy to the secondary star via the common envelope around the twostars. This transfer was parameterized by a transfer parameter (ratio ofthe observed and intrinsic luminosities of the primary star). We provethat this transfer parameter is a simple function of the mass andluminosity ratios. We introduced a new type of contact binary stars: Hsubtype systems which have a large mass ratio (q>0.72). These systemsshow behaviour in the luminosity ratio- transfer parameter diagram thatis very different from that of other systems and according to ourresults the energy transfer rate is less efficient in them than in othertypes of contact binary stars. We also show that different types ofcontact binaries have well defined locations on the mass ratio -luminosity ratio diagram. Several contact binary systems do not followLucy's relation (L2/L1 =(M2/M1)0.92). No strict mass ratio -luminosity ratio relation of contact binary stars exists.Tables 2 and 3 are available in electronic form athttp://www.edpsciences.org
| Period Changes of Two W UMa-Type Contact Binaries: RW Comae Berenices and CC Comae Berenices
From the present times of minimum light and those collected from theliterature, changes in the orbital period of the two W UMa-type contactbinaries RW Com and CC Com are analyzed. The results reveal that theperiod changes of these two systems show the same natures, with ashort-term oscillation superposed on the secular decrease. For RW Com,its period shows a secular decrease at a rate ofdP/dt=0.43×10-7 days yr-1. An oscillationwith a periodicity of 13.7 yr and an amplitude ofΔP=5.4×10-7 days is superposed on the seculardecrease. For CC Com, its period shows a secular decrease at a rate ofdP/dt=0.40×10-7 days yr-1. An oscillationwith a periodicity of 16.1 yr and an amplitude ofΔP=2.8×10-7 days is superposed on the seculardecrease. The period secular decreases of the two systems may beexplained by a mass-transfer rate of dm/dt=0.29×10-7Msolar yr-1 for RW Com anddm/dt=0.52×10-7 Msolar yr-1 forCC Com. The period short-term oscillations of the two systems may beexplained by the magnetic activity cycle model given by Applegate, andthe parameters for the magnetic activity cycle model are presented.
| A Possible Explanation of the O'Connell Effect in Close Binary Stars
A theoretical model for explaining the O'Connell effect of close binarystars is given based on the hypothesis that the circumstellar materialof a binary system is captured by its components. The results inferredfrom the model suggest that late-type and/or short-period binaries caneasily produce obvious O'Connell effect and that the occurrence ofO'Connell effect has no relation with the type of binaries. Theseconclusions are in agreement with the observed results. The observedO'Connell effects of six binary systems are examined by the model. Forthree W-subtype W UMa binaries (YY Eri, BX Per and SW Lac), thedensities of the materials captured by the two components are assumed tobe equal, and the calculated O'Connell effect is found to be almostequal to the observed effect. For three A-subtype W UMa systems (CNAnd, FG Hya and AU Ser), the two densities are assumed to be different,and are calculated separately. The calculated O'Connell effect turns outto agree better with the observed effect than that was formerlyobtained.
| Erdgebundene gegenuber Satelliten-Beobachtung.
Not Available
| On the performance of GAIA on photometry of eclipsing binaries: The case of four near-contact and contact systems
The light curves of four eclipsing binaries (two near-contact and twocontact) are analysed by means of light curve synthesis techniques toderive the geometric and photometric elements and the physicalparameters of the systems. For the analysis we used ground basedphotometric observations and Hipparcos/Tycho photometric data, whichmimic the photometric observations that should be obtained by GAIA, theapproved Cornerstone 6 mission by ESA. The results are compared and theachievable precision of the basic stellar parameters derived by GAIAphotometry is discussed.
| The 7.5 Magnitude Limit Sample of Bright Short-Period Binary Stars. I. How Many Contact Binaries Are There?
A sample of bright contact binary stars (W UMa type or EW, and related:with β Lyr light curves, EB, and ellipsoidal, ELL-in effect, allbut the detached, EA) to the limit of Vmax=7.5 mag is deemedto include all discoverable short-period (P<1 day) binaries withphotometric variation larger than about 0.05 mag. Of the 32 systems inthe final sample, 11 systems have been discovered by the Hipparcossatellite. The combined spatial density is evaluated at(1.02+/-0.24)×10-5 pc-3. The relativefrequency of occurrence (RFO), defined in relation to the main-sequencestars, depends on the luminosity. An assumption of RFO~=1/500 forMV>+1.5 is consistent with the data, although the numberstatistics is poor with the resulting uncertainty in the spatial densityand the RFO by a factor of about 2. The RFO rapidly decreases forbrighter binaries to a level of 1/5000 for MV<+1.5 and to1/30,000 for MV<+0.5. The high RFO of 1/130, previouslydetermined from the deep OGLE-I sample of disk population W UMa typesystems toward Baade's window, is inconsistent with and unconfirmed bythe new results. Possible reasons for the large discrepancy arediscussed. They include several observational effects but also apossibility of a genuine increase in the contact-binary density in thecentral parts of the Galaxy. Based on data from the Hipparcos satellitemission and from the David Dunlap Observatory, University of Toronto.
| 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.
| AD Cancri: A Contact Binary with Components in Poor Thermal Contact
We present the light curve and photometric solutions of the contactbinary AD Cnc. The light curve appears to exhibit a typical O'Connelleffect, with Maximum I brighter than Maximum II by 0.010 mag. in V. From1987 to 2000, the light curve showed changes of shape: the depth of theprimary eclipse increased by about 0.056m while that of thesecondary eclipse decreased by about 0.032m, so thedifference between the primary and the secondary eclipses increased byabout 0.088m, while there was no obvious variation in theO'Connell effect. Using the present and past times of minimum light, thechanges in the orbital period of the system are analyzed. The resultreveals that the orbital period of AD Cnc has continuously increased ata rate of {d p}/{d t}=4.4× 10-7 day yr-1.The light curve is analyzed by means of the latest version of theWilson-Devinney code. The results show that AD Cnc is a W-subtypecontact binary with a small mass ratio of 0.267 and the two componentsare in poor thermal contact. AD Cnc has a component temperaturedifference exceeding 500K, and exhibits a shallow contact of 3.6%. Theasymmetry of the light curves is explained by the star spot model. Wepresent the equivalent widths of 15 extrasolar-planet host stars.Thesedata were based on the high-resolution, high signal-to-noise ratiospectra obtained with the 2.16m telescope at Xinglong station. The errorin the Xinglong equivalent width is estimated by a comparison of thesedata with those given in previous studies of common stars.
| UBV Photometric Study of the Eclipsing Binary DM Delphini
The near-contact system DM Del with an A2V primary and a G8 secondarywas observed in U, B and V wavelengths in July 1998. A new seasonallight curve is presented and a new observed time of minimum is given.The unperturbed part of the light curve was used to determine some basicparameters of the system with the Wilson-Devinney code, some of whichwere kept fixed for spot modelling of the light curves. A simple spotdistribution was determined, based on a model with two cool spots on thesurface of the secondary. Absolute elements were calculated and theevolutionary status was determined.
| V432 Persei: A Contact Binary with Components in Poor Thermal Contact
CCD photometric observation of the short-period eclipsing binary V432Persei was carried out in the B and V bands at the Yunnan Observatory ofChina. The light curves of the system are obviously asymmetrical, withthe primary maximum brighter than the secondary maximum, which is knownas the O'Connell effect. The presented light curves are analyzed bymeans of the latest version of the Wilson-Devinney program. A grid ofsolutions for several fixed values of the mass ratio was calculated. Thebest fitting possible is for a mass ratio of 0.269 and a low degree ofcontact. The results show that V432 Per is seen to be a W-subtype WUrsae Majoris contact binary in poor thermal contact. The differencebetween the mean temperatures of the components is about 850 K. Theasymmetry of the light curves is explained by a cool spot on thesecondary component. The nature of the overluminosity of the secondaryof the system suggests that there should be very great energy transferfrom the primary to the secondary.
| Long-term photometry of the near-contact detached binary GR Tauri
We present photometric observations of the eclipsing binary GR Tau madein 1985, 1993, 1998, 2000 and 2001. New times of minima and ephemeridesare given. Based on a statistical analysis of the times of minimaobtained by photoelectric and CCD photometry, the orbital period of thesystem is found to be decreasing with a rate of Delta P/P = 3.27*E-10 during the past decades. An assumed hot spot on thetrailing hemisphere of the secondary enables us to reconstruct thepeculiar asymmetry of the distorted light curves. The photometricsolution with the Wilson-Devinney code reveals that GR Tau is anear-contact detached system with the two components almost fillingtheir respective critical Roche lobes. The photometric mass ratio turnsout to be q=0.22, and the masses and radii are derived for thecomponents as M1=1.42+/- 0.18 Msun,M2=0.31+/- 0.04 Msun, R1=1.47+/- 0.19Rsun and R2=0.70+/- 0.09 Rsun. Theauthors discuss the possible evolutionary status of the component starsand the probable nature of the assumed hot spot. Tables A.1 to A.3 areonly available in electronic at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/395/587
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| 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.
| CN Andromedae: A Broken-Contact Binary?
We solve new UBV light curves of the eclipsing binary CN Andromedaesimultaneously with radial velocities by the method of differentialcorrections. We find it semidetached with the more massive star fillingits limiting lobe and the less massive star very close to lobe-filling.Our solutions of earlier light curves have the same configuration.Within the uncertainties, the system may be in a broken or a marginalcontact stage as it undergoes thermal relaxation oscillations. The lightcurves are strongly affected by a large dark spot at high latitude onthe more massive star and by a bright substellar spot on the companion.Spot locations and temperatures do not differ significantly from epochto epoch. Based on single star evolutionary models, the primary's mass(1.299+/-0.045 Msolar) and radius (1.425+/-0.016Rsolar) are consistent with those of a star of age2.9×109 yr that will leave the main sequence in another2.0×109 yr. The orbital period has decreased during thepast 50 yr according to traditional eclipse timings and also accordingto our generalized light and velocity solutions that include a referenceepoch T0 and a rate of period change dP/dt. We finddP/dt=-0.01951+/-0.00054 s yr-1, which is consistent withmass transfer from the more to the less massive star of1.4×10-7 Msolar yr-1, assuming nomass is lost from the system. Reliable absolute dimensions aredetermined.
| KW Persei - a near-contact system?
An analysis of UBV photoelectric photometry for the eclipsing binary KWPer based on new observational data is presented. The light changes arenot only due to eclipses, but also to activity in the system. The U, Band V light curves are analyzed by the Binary Maker 2.0 andWilson-Devinney codes to derive the geometrical and physical parametersof the system. Since the O'Connell effect is present on the light curvesin the three colours, the unperturbed parts of the light curves areconsidered to represent the quiet stage of the system, in contrast tothe active stage which is represented by the perturbed parts of thelight curves. The discussion about the evolutionary status of the systemindicates that the secondary component of the binary system is anevolved star and the primary is a MS star. Table 4 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/373/950
| A Photometric study of the near-contact system RU Ursae Minoris
The near-contact system RU UMi with an F0 primary and a K5 secondary wasobserved in U, B and V wavelengths in May and July 1998, as well as inMarch, May and July 1999. Six new observed times of minima are given anda new ephemeris is proposed. The basic parameters of the systemextracted by our observations were used for spot modelling of the lightcurves. A simple spot distribution was determined, based on a model withone relatively small cool spot on the surface of the secondary. Absoluteelements were calculated and the evolutionary status was determined. Ourdata favor a semi-detached configuration, with the secondary filling itsinner Roche lobe; the primary must also be near the limits of its lobe.Table 2 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strabg.fr(130.79.128.5)} or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qeat?/A+A/369/960
| 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
| On the Variability of A3-F0 Luminosity Class III-V Stars
I investigate the Hipparcos Satellite photometry of A3-F0 stars ofluminosity classes III-V to learn about their variability and identify afew stars for which further study is desirable.
| Analysis of UBV Photometry of the Near-Contact Binary AK Canis Minoris
As a part of our study of eccentric eclipsing binary candidates, we haveobtained complete UBV photoelectric light curves of the neglected systemAK Canis Minoris. The observations were taken at Lowell Observatory in1994 February. Two new epochs of minimum light were determined fromthese observations. A period study, spanning 33 years, was undertaken,and both improved linear and quadratic ephemerides were obtained. Therobust period decrease determined in the quadratic ephemeris may implymagnetic braking arising from the solar-type secondary component. UBVlight curves formed from our precision observations are presented. Thefirst synthetic light-curve solution of AK CMi is presented. Ouranalysis reveals that AK CMi is in a near-contact, semidetachedconfiguration with an A3 spectral type primary component and a K2secondary filling its Roche lobe. Contrary to earlier reports that AKCMi has a displaced secondary eclipse, our secondary eclipse occurs atphase 0.5.
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Identification of lambda Bootis stars using IUE spectra. I. Low resolution data
An analysis of the stars included in the catalogue of lambda Bootisstars by Paunzen et al. (1997) and which also have IUE observations ispresented here. Population I A-F type stars as well as field horizontalbranch stars were also included in the analysis. Using line-ratios ofcarbon to heavier elements (Al and Ni) allows us to establishunambiguous membership criteria for the lambda Bootis group. Tables 1-3are only available in electronic form at CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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