תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
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 Apparent Descriptive Method for Judging the Synchronization of Rotation of Binary Stars
The problem of the synchronous rotation of binary stars is judged byusing a synchronous parameter Q introduced in an apparent descriptivemethod. The synchronous parameter Q is defined as the ratio of therotational period to the orbital period. The author suggests severalapparent phenomenal descriptive methods for judging the synchronizationof rotation of binary stars. The first method is applicable when theorbital inclination is well-known. The synchronous parameter is definedby using the orbital inclination i and the observable rotationalvelocity (V1,2 sin i)M. The method is mainly suitable for eclipsingbinary stars. Several others are suggested for the cases when theorbital inclination i is unknown. The synchronous parameters are definedby using a1,2 sin i,m1,2 sin3 i, the mass function f (m) andsemi-amplitudes of the velocity curve, K1,2 given in catalogue ofparameters of spectroscopic binary systems and (V1,2 sin i)M. Thesemethods are suitable for spectroscopic binary stars including those thatshow eclipses and visual binary stars concurrently. The synchronousparameters for fifty-five components in thirty binary systems arecalculated by using several methods. The numerical results are listed inTables 1 and 2. The statistical results are listed in Table 3. Inaddition, several apparent descriptive methods are discussed.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| 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
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
| 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.
| Comparison of Parallaxes from Eclipsing Binaries Method with Hipparcos Parallaxes
The parallaxes determined by Lacy (1979) by means of eclipsing binariesmethod are compared with the Hipparcos parallaxes for 19 systems. Theresidual scatter of the distance moduli inferred from eclipsing binariesmethod - after allowing for known errors as given by Lacy and Hipparcos- is equal to 0.18 mag. It decreases to 0.08 mag when obviously notfitting semi-detached systems and systems with chromospheric activity ofcomponents are removed from the sample.
| Absolute Dimensions of Eclipsing Binaries. XXIII. The F-Type System EI Cephei
We report new radial velocity measurements made with theHarvard-Smithsonian Center for Astrophysics Digital Speedometers of theF-type double-lined eclipsing binary EI Cep (P=8.4 days), in which thesecondary is a metallic-line star. Using these and previous measurementsfrom the literature, we redetermine the masses of the components to aprecision of 0.4%, 4 to 5 times better than previously achieved. We alsoreanalyze UBV light curves for the system from the literature withmodern methods to determine the radii and the effective temperatures.The resulting stellar parameters are MA=1.7716+/-0.0066Msolar, MB=1.6801+/-0.0062 Msolar,RA=2.896+/-0.048 Rsolar,RB=2.329+/-0.044 Rsolar,TAeff=6750+/-100 K, andTBeff=6950+/-100 K. Further properties of thesystem are given in this paper. Both components are near the end oftheir main-sequence evolution, and a comparison of the observationalresults with theoretical evolutionary models gives excellent agreementwith models using two somewhat different treatments of overshooting fromthe convective cores (but not with standard models). An age of 1.4 Gyris derived for the roughly solar metallicity indicated by our lowsignal-to-noise ratio spectra. A precise spectroscopic determination ofthe metallicity of EI Cep would be very useful to place even tighterconstraints on the models. The measured projected rotational velocitiesof the stars (13 and 17 km s-1 for EI Cep A and B,respectively) are very close to, but not quite synchronized with, theorbital motion. This is in agreement with predictions from current tidaltheories, which, however, also predict that orbital circularization hasnot yet occurred, although we detect no significant eccentricity. Someof the observations reported in this paper were obtained at the MultipleMirror Telescope Observatory, a facility operated jointly by theUniversity of Arizona and the Smithsonian Institution.
| Neglected binaries of special interest
Not Available
| 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.
| The calculation of critical rotational periods in three typical close binary systems based on synchronization theory.
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_.
| 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.
| Measurement and analysis of rotation in close binaries. II. Calculation of synchronism.
Not Available
| The active dynamo stars: RS CVn, BY Dra, FK Com, Algol, W UMa, and T Tau
Not Available
| Measurement and Analysis of Rotation in Close Binary Stars - Part One - Observations and Results
Not Available
| Catalogue of astrophysical parameters of binary systems
Not Available
| Photoelectric Minima of Eclipsing Binaries
Not Available
| Eclipsing binaries with eccentric orbits
Two groups of eclipsing binaries are dealt with: the first consists ofall binaries with enough data in the General Catalog of Variable Stars(GCVS; Cholopov et al, 1987), the other of those for which accurateparameters are known. In the first group, problems with classificationin GCVS are noticed and several examples of binaries with unexpectedparameters are named. For binaries of the second group, their fractionalradii, ages, and initial radii are used to discuss the relation of theirevolutionary status and orbital eccentricity. Dependence of eccentricityon spectral type and age is observed, and no peak in the initialeccentricity distribution at e = 0 seems to be present. It is suggestedthat binary origin by fragmentation followed by disruption of initialmultiple systems can explain all observed binaries, perhaps with theexception of contact systems in the main sequence. In several cases thecircularization must be due to mass transfer in the eccentric orbit.
| New strong evidence for the importance of convective overshooting in intermediate-mass stars
Major differences between current series of stellar evolutioncalculations concern their opacities and treatment of convection.Accurate mass, radius, luminosity, and abundance data from eclipsingbinaries now allow significant conclusions on these differences: binarystars with small convective cores are very well fitted by standardmodels using Los Alamos (but not Cox-Stewart) opacities. However, atjust slightly larger masses, the moderately evolved binaries clearlyrequire convective overshooting for a satisfactory fit. Precise radialvelocities for F-type turnoff stars in IC 4651 and NGC 3680 not onlyconfirm the signatures of overshooting observed in these clusters butalso show that any such firm conclusions require proper identificationof binaries and nonmembers. It is concluded that standard (and someovershooting) models are inconsistent with current precise data forintermediate-mass stars. Among the consequences of rejecting the oldermodels, it is pointed out that ages for stars younger than roughly 4 Gyrwill increase by up to 50-100 percent.
| An Update on EI Cephei and V377 Cassiopeiae
Updated information is given on the eclipsing binary EI Cephei and theunclassified variable V377 Cassiopeiae
| A Study of the DM and SD Type Eclipsing Variables by Means of the Cluster Analysis Technique
Not Available
| On 'the' spectral type-mass relation for main-sequence stars
The validity of a unique spectral type-mass relation for main-sequencestars is examined in some detail. In this connection, attention is givento the basis for the recent result by van Hamme and Wilson (1986) thatsystematic 'mass discrepancies' exist between directly determined('radial-velocity') masses and those ('spectral type masses') inferredfrom the spectral type-mass relation by Habets and Heintze (1981). It isshown that the apparent reality of these 'mass discrepancies' (and henceof their proposed dependence on chemical composition and stellarinternal structure) is primarily due to the use of a calibrationrelation which is only valid for stars in the lower part of themain-sequence band. It is also demonstrated that application of a meanspectrum-mass relation carries an inherent uncertainty of some + or - 15percent due to effects of evolution within the main-sequence band. Someexamples are given of the range of stellar properties within themain-sequence band and ways to improve the calibrations are discussed.
| Reexamination of the mass-radius relation of main sequence in binary systems
The mass-radius relation of the main sequence was reexamined using 171components of 88 double-lined detached binary systems with welldetermined absolute dimensions and masses. Empirical relations for theZAMS were obtained and compared with the theoretical models. Thepositions of the other 27 semidetached binaries in the log M - log Rdiagram are also discussed.
| Stellar masses and radii based on modern binary data
Accurate data on absolute dimensions of eclipsing binaries published inthe astronomical literature since 1980 are collected and analyzed.Simple approximation formulas relating the effective temperature withother basic physical parameters (mass, radius, bolometric magnitude) arederived. Mean and extreme values of these parameters for each spectraltype are also tabulated. The implication of improved data for theproblem of critical rotational periods and equatorial velocities ofearly-type stars is discussed.
| Nonstationary Phenomena in Eclipsing Detached Main Sequence Binaries
Not Available
| Period changes in EI Cephei
A new period (P = 8.439422 d) of the eclipsing binary system EI Cepheihas been given, which is based on all available times of minima. Periodsusing Strohmeier's (1958) epoch have also been presented for theobservations given by other investigators. Period based on onlyphotoelectric minima comes out to 8.439336 d, which is less than theearlier periods given in the literature. O-C diagrams of EI Cephei havebeen presented for the first time, and period variations have beenestimated in different portions of the O-C diagram of EI Cephei.
| Rediscussion of eclipsing binaries. XVI - The detached early A type binaries PV Cassiopeiae and WX Cephei
The available spectrographic and photometric material for PV Cas (B9.5)and WX Cep (A3) is analyzed to obtain the properties of the stars. Thisstudy completes the presentation of Lick coude material on detachedbinaries in the range late B-A. The nearly equal components of PV Casare cooler than predicted by evolutionary models with helium abundance'primordial' or greater, an effect noted also for other A type binaries.WX Cep appears to be a short-lived evolutionary state. The slightly moremassive star has completed core hydrogen burning, while the less massivehas not.
| Eclipsing Binaries - Cancer to Corona Borealis in 1972-1984
Not Available
| Close binary mass anomalies and metallicity
Direct (radial velocity) and indirect (spectral type, luminosity class)mass determinations for luminosity class V binaries are compared. Theexistence of statistical biases or apparently irreconcilable individualdiscrepancies, or both, in the data is examined, and their explanationby astrophysical effects such as chemical composition and agedifferences is considered. The existence of residual discrepancies,after correction for chemical composition effects and statisticalallowance for age effects, which could only be due to otherastrophysical effects, to instrumental effects, or to selection effects,is investigated. A need for at least one additional astrophysicaleffect, suspected to be fast core rotation, is found in a few binaries.It is argued that some remaining evidence for systematic observationalerrors is more likely to be the result of selection effects rather thanan instrumental effect.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קפיאוס |
| התרוממות ימנית: | 21h28m28.21s |
| סירוב: | +76°24'12.6" |
| גודל גלוי: | 7.604 |
| מרחק: | 198.807 פארסק |
| תנועה נכונה: | -4.4 |
| תנועה נכונה: | -12.6 |
| B-T magnitude: | 8.056 |
| V-T magnitude: | 7.642 |
קטלוגים וכינוים:
|
INHABITED SKY
