Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
Radial Velocity Studies of Close Binary Stars. XI.
Radial-velocity measurements and sine-curve fits to orbital radialvelocity variations are presented for 10 close binary systems: DU Boo,ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi, andAG Vir. With this contribution, the David Dunlap Observatory program hasreached the point of 100 published radial velocity orbits. The radialvelocities have been determined using an improved fitting technique thatuses rotational profiles to approximate individual peaks in broadeningfunctions. Three systems, ET Boo, VW LMi, and TV UMi, are found to bequadruple, while AG Vir appears to be a spectroscopic triple. ET Boo, amember of a close visual binary with Pvis=113 yr, waspreviously known to be a multiple system, but we show that the secondcomponent is actually a close, noneclipsing binary. The new observationshave enabled us to determine the spectroscopic orbits of the companion,noneclipsing pairs in ET Boo and VW LMi. A particularly interesting caseis VW LMi, for which the period of the mutual revolution of the twospectroscopic binaries is only 355 days. While most of the studiedeclipsing pairs are contact binaries, ET Boo is composed of twodouble-lined detached binaries, and HL Dra is a single-lined detached orsemidetached system. Five systems of this group have been observedspectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-linedbinary), V566 Oph, and AG Vir, but our new data are of much higherquality than in the previous studies.Based on data obtained at the David Dunlap Observatory, University ofToronto, Canada.
| 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.
| On the Period Variation of the W UMa-type Contact Binary V502 Ophiuchi
The variation in the orbital period of the W UMa type contact binaryV502 Oph is analyzed. The orbital period exhibits a wavelike variationwith a periodicity of 23.0 years and an amplitude of ΔP =1.24×10-6 days superimposed on secular decrease ofdP/dt = 1.68×10-7 day per year. The long-term decreasemay be accompanied by the contraction of the secondary at a rate of 83 mper year and a mass transfer rate from the primary to the secondary of4.28×10-8Modot per year. The short-termoscillation may be explained by the presence of a third component.Orbital elements of the third body and its possible mass are presented.
| 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.
| Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation
We study the kinematics of 129 W UMa binaries and we discuss itsimplications on the contact binary evolution. The sample is found to beheterogeneous in the velocity space. That is, kinematically younger andolder contact binaries exist in the sample. A kinematically young (0.5Gyr) subsample (moving group) is formed by selecting the systems thatsatisfy the kinematical criteria of moving groups. After removing thepossible moving group members and the systems that are known to bemembers of open clusters, the rest of the sample is called the fieldcontact binary (FCB) group. The FCB group is further divided into fourgroups according to the orbital period ranges. Then, a correlation isfound in the sense that shorter-period less-massive systems have largervelocity dispersions than the longer-period more-massive systems.Dispersions in the velocity space indicate a 5.47-Gyr kinematical agefor the FCB group. Compared with the field chromospherically activebinaries (CABs), presumably detached binary progenitors of the contactsystems, the FCB group appears to be 1.61 Gyr older. Assuming anequilibrium in the formation and destruction of CAB and W UMa systems inthe Galaxy, this age difference is treated as an empirically deducedlifetime of the contact stage. Because the kinematical ages (3.21, 3.51,7.14 and 8.89 Gyr) of the four subgroups of the FCB group are muchlonger than the 1.61-Gyr lifetime of the contact stage, the pre-contactstages of the FCB group must dominantly be producing the largedispersions. The kinematically young (0.5 Gyr) moving group covers thesame total mass, period and spectral ranges as the FCB group. However,the very young age of this group does not leave enough room forpre-contact stages, and thus it is most likely that these systems wereformed in the beginning of the main sequence or during thepre-main-sequence contraction phase, either by a fission process or mostprobably by fast spiralling in of two components in a common envelope.
| 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
| Photoelectric Minimum Times of Some Eclipsing Binary Stars
We present 24 minimum times of 7 eclipsing binaries observed in theyears from 2001 to 2003.
| Catalogue of the field contact binary stars
A catalogue of 361 galactic contact binaries is presented. Listedcontact binaries are divided into five groups according to the type andquality of the available observations and parameters. For all systemsthe ephemeris for the primary minimum, minimum and maximum visualbrightness and equatorial coordinates are given. If available,photometric elements, (m1+m2)sin3i,spectral type, parallax and magnitude of the O'Connell effect are alsogiven. Photometric data for several systems are augmented by newobservations. The quality of the available data is assessed and systemsrequiring modern light-curve solutions are selected. Selectedstatistical properties of the collected data are discussed.
| CCD Minima for Selected Eclipsing Binaries in 2002
Not Available
| 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.
| 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.
| ROSAT all-sky survey of W Ursae Majoris stars and the problem of supersaturation
From ROSAT all-sky survey (RASS) data we obtained X-ray fluxes for 57 WUMa type contact systems. In our sample we detected three stars whichare the shortest period main sequence binaries ever found as X-raysources. For stars with (B-V)_0 < 0.6 the normalized X-ray fluxdecreases with a decreasing color index but for (B-V)_0 > 0.6 aplateau is reached, similar to the saturation level observed for single,rapidly rotating stars. The X-ray flux of W UMa stars is about 4-5 timesweaker than that of the fastest rotating single stars. Because earlytype, low activity variables have longer periods, an apparentperiod-activity relation is seen among our stars, while cool stars with(B-V)_0 > 0.6 and rotation periods between 0.23 and 0.45 days do notshow any such relation. The lower X-ray emission of the single, ultrafast rotators (UFRs) and W UMa stars is interpreted as the result of adecreased coronal filling factor. The physical mechanisms responsiblefor the decreased surface coverage differs for UFRs and W UMa systems.For UFRs we propose strong polar updrafts within a convection zone,driven by nonuniform heating from below. The updrafts should beaccompanied by large scale poleward flows near the bottom of theconvective layer and equatorward flows in the surface layers. The flowsdrag dynamo generated fields toward the poles and create a field-freeequatorial region with a width depending on the stellar rotation rate.For W UMa stars we propose that a large scale horizontal flow embracingboth stars will prevent the magnetic field from producing long-livedstructures filled with hot X-ray emitting plasma. The decreased activityof the fastest rotating UFRs increases the angular momentum loss timescale of stars in a supersaturated state. Thus the existence of a periodcutoff and a limiting mass of W UMa stars can be naturally explained.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| V1073 Cygni: A New Light Curve and Analysis
A new CCD light curve of the A-type W UMa star V1073 Cygni has beenobtained, and the differential-corrections method of Wilson and Devinneywas used to compute a new set of system parameters. The same analysishas been applied to the other photometric light curves in theliterature, including the Hipparcos light curve. A new ephemeris isdetermined for the times of primary minimum. V1073 Cygni probably hasinitially formed as a detached system and evolved into contact.
| Unstable Behavior of the W UMa-Type Contact Binary V1073 Cygni
Observational evidence of unstable behavior for the W UMa-type binarysystem V1073 Cygni is presented in this paper. Having collected 111times of minimum light during 1930-1998, we analyzed the change in theorbital period of this system. A period decrease was detected. Comparingthe photoelectric observations in 1963-64 with that made in 1988-91,obvious variable O'Connell effect of the light curves in V can be seen.Possible reasons for the unstable behavior of V1073 Cyg were discussed.
| New Times of Minima and Updated Ephemerides of Selected Contact Binaries
We present new times of minima of 44i Boo, AB And, SW Lac, U Peg VW Cepand XY Leo. Besides these stars, we also give updated ephemerides of OOAql, DK Cyg, LS Del and V1073 Cyg.
| New variable chemically peculiar stars identified in the HIPPARCOS archive
Since variability of chemically peculiar (CP) stars plays an importantrole for the astrophysical explanation of their outstanding behaviour,we have identified new variable CP stars listed in Renson's catalogueusing the extensive Hipparcos Variability Annex. From the 293 objectsfound, 33 were excluded because they are no CP stars and/or have noperiod listed, half of the remaining stars are newly identified and halfhad been already included in the catalogue of variable CP stars by\cite[Catalano & Renson (1997).]{Ca} Most of the newly identifiedvariability is due to an apparent magnetic field coupled with stellarrotation (oblique rotator model). The constraints of this model arefulfilled for all but three CP2 stars. Variations of bona fide Am-Fmstars are exclusively explained by eclipses of binary systems.Furthermore eight candidates of the >~mma Doradus group (pulsatingAm-Fm stars) were detected. Based on data from the ESA Hipparcosastrometry satellite. Table 1 is also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia\break http://cdsweb.u-strasbg.fr/Abstract.html
| Photoelectric Minima of Selected Eclipsing Binaries
Not Available
| Absolute Magnitude Calibration for the W UMa-Type Systems Based on HIPPARCOS Data
Hipparcos parallax data for 40 contact binary stars of the W UMa-type(with epsilon M_V < 0.5) are used to derive a new, (B-V)-basedabsolute-magnitude calibration of the form M_V = M_V(log P,B-V). Thecalibration covers the ranges 0.26 < (B-V)_0 < 1.14, 0.24 < P< 1.15 day, and 1.4 < M_V < 6.1; it is based on a solutionweighted by relative errors in the parallaxes (2.7% to 24%). Previouscalibrations have not been based on such a wide period and color space,and while they have been able to predict M_V with sufficient accuracyfor systems closely following the well-known period-color relation, thenew calibration should be able to give also good predictions for moreexotic ``outlying'' contact binary systems. The main limitations of thiscalibration are the inadequate quality of the ground-based photometricdata, and the restriction to the (B-V) index, which is more sensitive tometallicity effects than the (V-I) index; metallicities are, however,basically unknown for the local W UMa-type systems. (SECTION: Stars)
| On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. II. Metallicity and pseudo-synchronization.
We reveal sufficient evidences that for Am binaries the metallicitymight depend on their orbital periods, P_orb_, rather than on vsini. Inparticular, δm_1_ index seems to decrease with increasing orbitalperiod up to at least P_orb_=~50d, probably even up to P_orb_=~200d.This gives further support to our "tidal mixing + stabilization"hypothesis formulated in Part I. Moreover, while the most metallic Amstars seem to have rather large periods the slowest rotators are foundto exhibit substantially shorter P_orb_. A questioning eye is thus caston the generally adopted view that Am peculiarity is caused by asuppressed rotationally induced mixing in slowly rotating `single'stars. The observed anticorrelation between rotation and metallicity mayhave also other than the `textbook' explanation, namely being the resultof the correlation between metallicity and orbital period, as themajority of Am binaries are possibly synchronized. We further argue thatthere is a tendency in Am binaries towards pseudo-synchronization up toP_orb_=~35d. This has, however, no serious impact on our conclusionsfrom Part I; on the contrary, they still hold even if this effect istaken into account.
| Photoelectric Minima of Some Eclipsing Binaries
Not Available
| On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.
The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_.
| Revised Photometric Analysis of the Eclipsing Binary V 1073 Cygni
Not Available
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Are Contact Binaries Undergoing Thermal Relaxation Oscillations with Contact Discontinuity?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....110..782W&db_key=AST
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
Not Available
| A photometric study of the eclipsing binary V 1073 CYGNI
Photoelectric observations of the eclipsing binary V 1073 Cyg have beencarried out in B and V colors at the Ege University Observatory. Thelight curves were analyzed with the Wilson-Devinney approach. A periodstudy reveals that the orbital period of the system is decreasing at therate of (3.21 +/- 0.17) second per century.
| Studies of late-type binaries. V - The orbit and physical parameters of V 1073 Cygni
From a new spectroscopic orbit of the A-type WUMa system V 1073 Cyg,based on Reticon observations, the following values are found:V0 = -0.8 +/- 1.1 km/s; Kp = 66.7 +/- 1.3 km/s; Ks = 210.2+/- 1.2 km/s; and mp/m sub s = 3.15 +/- 0.07. Combiningresults on the mean secondary temperature, filling factor, andinclination with the spectroscopic orbit, the physical parameters of V1073 Cyg are obtained.
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Лабуд |
| Ректацензија: | 21h25m00.36s |
| Deклинација: | +33°41'15.0" |
| Apparent магнитуда: | 8.39 |
| Даљина: | 183.824 parsecs |
| Proper motion RA: | -4.7 |
| Proper motion Dec: | -21 |
| B-T magnitude: | 8.871 |
| V-T magnitude: | 8.43 |
Каталог и designations:
|
