תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Does convective core overshooting depend on stellar mass?. Tests using double-lined eclipsing binaries
Aims.We have selected 13 double-line eclipsing binary systems (DLEBS),strategically positioned in the HR diagram, to infer the mass dependenceof the core overshooting parameter α_ov. Methods: In order tocompare the data from these DLEBS with the theoretical predictions wecomputed four grids of evolutionary stellar models with variable amountsof core overshooting (α_ov = 0.0, 0.2, 0.4, and 0.6) in additionto those previously computed. In some particular cases specific modelswere computed for the precise observed masses. This procedure avoidsinterpolations and extrapolations, and only considers chemicalcompositions within the limits of the usual primordial helium abundanceand enrichment law. Results: We used the ratio TR ≡ Teff2/Teff 1 instead of the effective temperaturesthemselves as we consider it a much better constrained parameter. Thisis because it is directly derived from the analysis of light curves andis independent of calibrations, distances, and model atmospheres. Incontrast to previous studies on the subject, we have found that standardmodels or models with moderate core overshooting (α_ov ≈ 0.2)are able to match the absolute dimensions of key DLEBS such as V380 Cygor V453 Cyg. The resulting log M - α_ov diagram indicates that thedependence of α_ov on mass is more uncertain and less pronouncedthat previously established. This result is also consistent with theanalysis of colour-magnitude diagrams for clusters and with previouscomparisons of stellar models with larger samples of DLEBS.Figures 1-12 are only available in electronic form athttp://www.aanda.org
| The early-type close binary CV Velorum revisited
Aims.Our goal was to improve the fundamental parameters of the massiveclose double-lined eclipsing B2.5V+B2.5V binary CV Velorum. Methods: Wegathered new high-resolution échelle spectroscopy on 13 almostconsecutive nights covering two orbits. We computed a simultaneoussolution to all the available high-quality radial-velocity and lightdata with the latest version of the Wilson-Deviney code. Results: Weobtained the following values for the physical parameters: M1= 6.066(74)~M_ȯ, M2 = 5.972(70)~M_ȯ, R1= 4.126(24)~R_ȯ, R2 = 3.908(27)~R_ȯ, logL1 = 3.20(5)~L_ȯ, and log L2 =3.14(5)~L_ȯ. The quoted errors contain a realistic estimate ofsystematic uncertainties mainly stemming from the effective temperatureestimation. We derived abundances for both components and found them tobe compatible with those of B stars in the solar neighbourhood. Wediscovered low-amplitude periodic line-profile variations with theorbital frequency for both components. Their interpretation requires newdata with a longer time span. The primary rotates subsynchronously whilethe secondary's v sin i and radius are compatible with synchronousrotation. We provide an update of the empirical mass-luminosity relationfor main-sequence B stars which can be used for statistical predictionsof masses or luminosities.Based onspectroscopic observations gathered with the CORALIE spectrographmounted onthe 1.2 m Euler telescope at La Silla, Chile.
| Absolute dimensions of eclipsing binaries. XXIV. The Be star system DW Carinae, a member of the open cluster Collinder 228
Context: The study of detached eclipsing binaries which are members ofstellar clusters is is a powerful way of determining the properties ofthe cluster and of constraining the physical ingredients of theoreticalstellar evolutionary models. Aims: DW Carinae is a close but detachedearly B-type eclipsing binary in the young open cluster Collinder 228.We have measured accurate physical properties of the components of DWCar (masses and radii to 1%, effective temperatures to 0.02 dex) andused these to derive the age, metallicity and distance of Collinder 228. Methods: The rotational velocities of both components of DW Car arehigh, so we have investigated the performance of double-Gaussianfitting, one- and two-dimensional cross-correlation and spectraldisentangling for deriving spectroscopic radial velocites in thepresence of strong line blending. Gaussian and cross-correlationanalyses require substantial corrections for the effects of lineblending, which are only partially successful for cross-correlation.Spectral disentangling is to be preferred because it does not assumeanything about the shapes of spectral lines, and is not significantlyaffected by blending. However, it suffers from a proliferation of localminima in the least-squares fit. We show that the most reliable radialvelocities are obtained using spectral disentangling constrained by theresults of Gaussian fitting. Complete Strömgren uvby light curveshave been obtained and accurate radii have been measured from them bymodelling the light curves using the Wilson-Devinney program. Thisprocedure also suffers from the presence of many local minima inparameter space, so we have constrained the solution using an accuratespectroscopic light ratio. The effective temperatures and reddening ofthe system have been found from Strömgren photometric calibrations. Results: The mass and radius of DW Car A are MA = 11.34± 0.12 {M}_ȯ and RA = 4.558 ± 0.045{R}_ȯ. The values for DW Car B are MB = 10.63 ±0.14 {M}_ȯ and RB = 4.297 ± 0.055 {R}_ȯ.Strömgren photometric calibrations give effective temperatures of{T_eff}A = 27 900 ± 1000 K and {T_eff}B =26 500 ± 1000 K, and a reddening of Eb-y = 0.18± 0.02, where the quoted uncertainties include a contributionfrom the intrinsic uncertainty of the calibrations. The membership of DWCar in Cr 228 allows us to measure the distance, age and chemicalcomposition of the cluster. We have used empirical bolometriccorrections to calculate a distance modulus of 12.24 ± 0.12 magfor DW Car, which is in agreement with, and more accurate than,literature values. A comparison between the properties of DW Car and thepredictions of recent theoretical evolutionary models is undertaken inthe mass-radius and mass-T_eff diagrams. The model predictions match themeasured properties of DW Car for an age of about 6 Myr and a fractionalmetal abundance of Z ≈ 0.01.
| Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
| 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.
| Automatic classification of eclipsing binaries light curves using neural networks
In this work we present a system for the automatic classification of thelight curves of eclipsing binaries. This system is based on aclassification scheme that aims to separate eclipsing binary systemsaccording to their geometrical configuration in a modified version ofthe traditional classification scheme. The classification is performedby a Bayesian ensemble of neural networks trained with Hipparcos data ofseven different categories including eccentric binary systems and twotypes of pulsating light curve morphologies.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Observational Tests and Predictive Stellar Evolution. II. Nonstandard Models
We examine contributions of second-order physical processes to theresults of stellar evolution calculations that are amenable to directobservational testing. In the first paper in the series, we establishedbaseline results using only physics that were common to modern stellarevolution codes. In this paper we establish how much of the discrepancybetween observations and baseline models is due to particular elementsof new physics in the areas of mixing, diffusion, equations of state,and opacities. We then consider the impact of the observationaluncertainties on the maximum predictive accuracy achievable by a stellarevolution code. The Sun is an optimal case because of the precise andabundant observations and the relative simplicity of the underlyingstellar physics. The standard model is capable of matching the structureof the Sun as determined by helioseismology and gross surfaceobservables to better than a percent. Given an initial mass and surfacecomposition within the observational errors, and no current observablesas additional constraints for which the models can be optimized, it isnot possible to predict the Sun's current state to better than ~7%.Convectively induced mixing in radiative regions, terrestriallycalibrated by multidimensional numerical hydrodynamic simulations,dramatically improves the predictions for radii, luminosity, and apsidalmotions of eclipsing binaries while simultaneously maintainingconsistency with observed light element depletion and turnoff ages inyoung clusters. Systematic errors in core size for models of massivebinaries disappear with more complete mixing physics, and acceptablefits are achieved for all of the binaries without calibration of freeparameters. The lack of accurate abundance determinations for binariesis now the main obstacle to improving stellar models using this type oftest.
| Apsidal Motion in Binaries: Rotation of the Components
A sample of 51 separated binary systems with measured apsidal periodsand rotational velocities of the components is examined. The ranges ofthe angles of inclination of the equatorial planes of the components tothe orbital plane are estimated for these systems. The observed apsidalvelocities can be explained by assuming that the axes of rotation of thestars are nonorthogonal to the orbital plane in roughly 47% of thesystems (24 of the 51) and the rotation of the components is notsynchronized with the orbital motion in roughly 59% of the systems (30of 51). Nonorthogonality and nonsynchrony are defined as deviations from90° and a synchronized angular velocity, respectively, at levels of1 or more.
| Detached double-lined eclipsing binaries as critical tests of stellar evolution. Age and metallicity determinations from the HR diagram
Detached, double-lined spectroscopic binaries that are also eclipsingprovide the most accurate determinations of stellar mass, radius,temperature and distance-independent luminosity for each of theirindividual components, and hence constitute a stringent test ofsingle-star stellar evolution theory. We compile a large sample of 60non-interacting, well-detached systems mostly with typical errorssmaller than 2% for mass and radius and smaller than 5% for effectivetemperature, and compare them with the properties predicted by stellarevolutionary tracks from a minimization method. To assess the systematicerrors introduced by a given set of tracks, we compare the resultsobtained using three widely-used independent sets of tracks, computedwith different physical ingredients (the Geneva, Padova and Granadamodels). We also test the hypothesis that the components of thesesystems are coeval and have the same metallicity, and compare thederived ages and metallicities with the ones obtained by fitting asingle isochrone to the system. Overall, there is a good agreement amongthe different determinations, and we provide a comprehensive discussionon the sub-sample of systems which either present problems or haveestimated metallicities. Although within the errors the published trackscan fit most of the systems, a large degeneracy between age andmetallicity remains. The power of the test is thus limited because themetallicities of most of the systems are unknown. The full version ofTable 6 is only available in the electronic form athttp://www.edpsciences.org
| Determination of the Ages of Close Binary Stars on the Main Sequence from Evolutionary Model Stars of Claret and Gimenez
A grid of isochrones, covering a wide range of stellar ages from thezero-age main sequence to 10 billion years, is calculated in the presentwork on the basis of the model stars of Claret and Gimenez withallowance for convective overshoot and mass loss by the components. Theages of 88 eclipsing variables on the main sequence from Andersen'scatalog and 100 chromospherically active stars from Strassmeier'scatalog are calculated with a description of the method of optimuminterpolation. Comparisons with age determinations by other authors aregiven and good agreement is established.
| Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations
A list of 62 detached binaries having reliable data on the rotation ofthe line of apsides is considered. Theoretical estimates of the rate ofapsidal motion are obtained. These estimates are compared withobservational data. It is shown that cases in which the theoreticalestimate exceeds the observed value are several times more frequent thancases in which the theoretical value is lower than the observed one.This discrepancy increases when systems with more reliable observationaldata are considered.
| New results on the apsidal-motion test to stellar structure and evolution including the effects of dynamic tides
We revised the current status of the apsidal-motion test to stellarstructure and evolution. The observational sample was increased by about50% in comparison to previous studies. Classical and relativisticsystems were analyzed simultaneously and only systems with accurateabsolute dimensions were considered. New interior models incorporatingrecent opacity tables, stellar rotation, mass loss, and moderate coreovershooting were used as theoretical tools to compare the predictedwith the observed shifts of the position of the periastron. The stellarmodels were computed for the precise observed masses and the adoptedchemical compositions are consistent with the corresponding tables ofopacities to avoid the inherent problems of interpolation in mass and in(X, Z). The derived chemical composition for each individual system wasused to infer the primordial helium content as well as a law ofenrichment. The values found are in good agreement with those obtainedfrom various independent sources. For the first time, the effects ofdynamic tides are taken into account systematically to determine thecontribution of the tidal distortion to the predicted apsidal-motionrate. The deviations between the apsidal-motion rates resulting from theclassical formula and those determined by taking into account theeffects of dynamic tides are presented as a function of the level ofsynchronism. For systems close to synchronisation, dynamic tides causedeviations with respect to the classical apsidal-motion formula due tothe effects of the compressibility of the stellar fluid. For systemswith higher rotational angular velocities, additional deviations due toresonances arise when the forcing frequencies of the dynamic tides comeinto the range of the free oscillation modes of the component stars. Theresulting comparison shows a good agreement between the observed andtheoretical apsidal-motion rates. No systematic effects in the sensethat models are less mass concentrated than real stars and nocorrelations with the evolutionary status of the systems were detected.
| Calculation of the masses of the binary star HD 93205 by application of the theory of apsidal motion
We present a method to calculate masses for components of both eclipsingand non-eclipsing binary systems as long as their apsidal motion ratesare available. The method is based on the fact that the equation thatgives the rate of apsidal motion is a supplementary equation that allowsthe computation of the masses of the components, if their radii and theinternal structure constants can be obtained from theoretical models.For this reason the use of this equation makes the method presented heremodel dependent . We apply this method to calculate the mass of thecomponents of the non-eclipsing massive binary system HD 93205 , whichis suspected to be a very young system. To this end, we have computed agrid of evolutionary models covering the mass range of interest, andtaking the mass of the primary (M 1 ) as the only independentvariable, we solve the equation of apsidal motion for M 1 asa function of the age of the system. The mass of the primary that wefind ranges from for zero-age main-sequence models, which sets an upperlimit for M 1 , down to for an age of 2Myr. Accordingly, theupper limit derived for the mass of the secondary is in very goodagreement with the masses derived for other O8V stars occurring ineclipsing binaries.
| Observational Tests and Predictive Stellar Evolution
We compare 18 binary systems with precisely determined radii and massesfrom 23 to 1.1 Msolar and stellar evolution models producedwith our newly revised code TYCHO. ``Overshooting'' and rotationalmixing were suppressed in order to establish a baseline for isolatingthese and other hydrodynamic effects. Acceptable coeval fits are foundfor 16 pairs without optimizing for heavy-element or helium abundance.The precision of these tests is limited by the accuracies of theobserved effective temperatures. High-dispersion spectra and detailedatmospheric modeling should give more accurate effective temperaturesand heavy-element abundances. PV Cas, a peculiar early A system, EK CepB, a known post-T Tauri star, and RS Cha, a member of a young OBassociation, are matched by pre-main-sequence models. Predicted massloss agrees with upper limits from IUE for CW Cep A and B. Relativelypoor fits are obtained for binaries having at least one component in themass range 1.7
| Determination of the consistent and interdependent values of the basic characteristics of eclipsing variable systems components
An approximate approach for determining consistent and interdependentwith each other principal characteristics as well as the equatorialrotational velocity and the inclination angle of rotation axis of arotator to the line - of - sight for components of eclipsing variablesystems is suggested.
| 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.
| Chemical composition of eclipsing binaries: a new approach to the helium-to-metal enrichment ratio
The chemical enrichment law Y(Z) is studied by using detacheddouble-lined eclipsing binaries with accurate absolute dimensions andeffective temperatures. A sample of 50 suitable systems was collectedfrom the literature, and their effective temperatures were carefullyre-determined. The chemical composition of each of the systems wasobtained by comparison with stellar evolutionary models, under theassumption that they should fit an isochrone to the observed propertiesof the components. Evolutionary models covering a wide grid in Z and Ywere adopted for our study. An algorithm was developed for searching thebest-fitting chemical composition (and the age) for the systems, basedon the minimization of a χ2 function. The errors (andbiases) of these parameters were estimated by means of Monte Carlosimulations, with special care put on the correlations existing betweenthe errors of both components. In order to check the physicalconsistency of the results, we compared our metallicity values withempirical determinations, obtaining excellent coherence. Theindependently derived Z and Y values yielded a determination of thechemical enrichment law via weighted linear least-squares fit. Our valueof the slope, ΔY/ΔZ=2.2+/-0.8, is in good agreement withrecent results, but it has a smaller formal error and it is free ofsystematic effects. Linear extrapolation of the enrichment law to zerometals leads to an estimation of the primordial helium abundance ofYp=0.225+/-0.013, possibly affected by systematics in theeffective temperature determination.
| Estimating the ages of eclipsing variable DM-stars on the basis of the evolutionary star models by Maeder and Meynet
A set of isochrones covering a wide range of star ages from5\cdot106 to 1010 yr was built on the basis of thestellar models by A. Maeder and G. Meynet with overshooting and massloss for Population I stars with abundances (X, Y, Z) = 0.70, 0.28,0.02. The isochrones were used to compute the ages of 88 eclipsingvariable stars from the catalog by Andersen which lie on the mainsequence. The influence of initial data errors on the rezultes wasinvestigated. The ages derived are in good agreement with the results ofother authors.
| Apsidal Motion in Double Stars. I. Catalog
A catalog of 128 double stars with measured periods of apsidal motion iscompiled. Besides the apsidal periods, the orbital elements of binariesand physical parameters of components (masses, radii, effectivetemperatures, surface gravities) are given. The agreement of the apsidalperiods found by various authors is discussed.
| Asteroseismology of the beta Cephei stars. II. 12 (DD) Lacertae
Five pulsation modes are simultaneously excited in this well-known betaCephei star. Three of them, including the one with the largest light andradial-velocity amplitudes, form a triplet. The triplet is equidistantin frequency to within the errors of measurement, that is, 0.0003 d(-1). Explaining why the triplet should be so nearly equidistant turns outto be a real challenge to the theory. We investigate the following threeoptions: (1) rotational splitting, (2) an oblique magnetic pulsator, and(3) nonlinear phase lock. Unfortunately, apart from the frequencies, thedata are meager. Photometric indices yield the effective temperature andsurface gravity of rather low accuracy. In addition, the existingdeterminations of the spherical harmonic degree of even the strongestobserved mode are discrepant. Consequently, the model parameters are notwell constrained. We show that of the three above-mentioned options, theoblique pulsator model is unlikely because it would require excessivelystrong dipolar field or a special field geometry. The rotationalsplitting is a possibility, but only for an l = 2, p_0 mode in a modelwith specific values of the effective temperature and surface gravity.Finally, we note that the nonlinear phase lock may be the solution.However, verifying this depends on the progress of nonlinearcalculations.
| The apsidal motion test of stellar structure in relativistic systems.
We have compared observational data of apsidal motion rates forrelativistic eclipsing binaries with theoretical predictions based onstellar theoretical models. Ten double-lined eclipsing binaries withhigh quality light curves and radial velocities were selected. Theanalysis of the data available indicate that the predictions by theGeneral Relativity and the new stellar models are able to explain theshift in the periastron position. The two versions of thenon-symmetrical theory of gravitation were also investigated. The earlyversion of this theory (Moffat, 1984ApJ...287L..77M) is not supportedwhen contrasted with recent observational data since it predicts tooslow apsidal motion rates. The more recent version (Moffat,1989PhRvD..39..474M) presents several problems in its formulation, liketoo many degrees of freedom and some parameters for which there is nosevere physical constraint. Moreover, such a theory is not able topredict a priori the apsidal motion rates.
| Photometric versus empirical surface gravities of eclipsing binaries.
Systematic differences in photometric stellar surface gravitydetermination are studied by means of the comparison with empiricalvalues derived from detached double-lined eclipsing binaries.Photometric gravities were computed using Moon & Dworetsky(1985MNRAS.217..305M) grids based on Kurucz (1979ApJS...40....1K)atmosphere models, and empirical gravities were taken from Andersen(1991A&ARv...3...91A). Individual Stroemgren colours and βindices of each component of the binary system have to be taken intoaccount to correctly analyze the observed differences. A compilation ofdata on a sample containing 30 detached double-lined eclipsing binarieswith accurate (=~1-2%) determination of mass and radius and availableuvbyHbeta_ photometric data is also presented. Correction ofthe differences in terms of T_eff_ and logg for the range11000K
| Further critical tests of stellar evolution by means of double-lined eclipsing binaries
The most accurately measured stellar masses and radii come fromdetached, double-lined eclipsing binaries, as compiled by Andersen. Wepresent a detailed quantitative comparison of these fundamental datawith evolution models for single stars computed with our evolution code,both with and without the effects of enhanced mixing or overshootingbeyond the convective cores. We use the same prescription forovershooting that Schroder, Pols & Eggleton found to reproduce theproperties of zeta Aurigae binaries. For about 80 per cent of the 49binary systems in the sample, both sets of models provide a good fit toboth stars at a single age and metallicity within the observationaluncertainties. We discuss possible causes for the discrepancies in theother systems. For only one system, AI Hya, do the enhanced-mixingmodels provide a significantly better fit to the data. For two others(WX Cep and TZ For) the fit to the enhanced-mixing models is alsobetter. None of the other systems can individually distinguish betweenthe models with and without enhanced mixing. However, the number ofsystems in a post-main-sequence phase is in much better agreement withthe enhanced-mixing models. This test provides supportive evidence forextended mixing in main-sequence stars in the range 2-3Msolar.
| The line-profile variable λ Scorpii is a spectroscopic triple system.
An analysis of 278 spectra of the line-profile variable λ Scorpiileads to the following conclusions. λ Sco is the primary of abinary system. The radial-velocity variations have a peak-to-peakamplitude of ~60km/s and an orbital period of 5.959 days. The orbit isnot circular but has an eccentricity of 0.29. The 5.959^d^-binary systemprobably moves in orbit with another distant, as yet unknown third star.By means of three five-hour time series of high-resolution spectra, theoscillations of the rapidly rotating β Cephei-type main componentare investigated. Line-profile variations, which reveal travellingsubfeatures across the lines, are discovered. λ Sco is so far oneof the very few βCephei stars in which such a moving-bumpphenomenon is detected. Radial-velocity variations are derived from thedata and analysed to reveal a main oscillation frequency near4.66cycles/day, and some more candidate frequencies. λ Sco is anon-radially pulsating β Cephei star which rotatessupersynchronously. The characteristics of λ Sco and the ζOph stars are briefly addressed. Despite the common line-profilebehaviour, spectral type, and vsin(i), we find no evidence ofcircumstellar material around λ Sco.
| A calibration of Geneva photometry for B to G stars in terms of Teff, log G and [M/H]
We have used recent Kurucz models and numerous standard stars to improvethe calibration of the Geneva photometric system proposed a few yearsago. A new photometric diagram for the classification of intermediatestars (8500 <= Teff <= 11000 K) is proposed and fills agap that the previous calibration had left open. Evidence is given for aclear inadequacy of the new Kurucz models in the region of the parameterspace where convection begins to take over radiation in the star'satmosphere. This problem makes the determination of the surface gravitydifficult, but leaves that of the other parameters apparentlyunaffected. The determination of metallicity is considerably improved,thanks to the homogeneous spectroscopic data published recently by\cite[Edvardsson et al. (1993)]{ref23}. Instead of showing thetraditional diagrams, we chose to publish the diagrams of the physicalparameters with the inverted grids inside, i.e. the lines of constantphotometric parameters.
| Improved Elements for Vv-Orionis
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.
| On the absolute brightnesses and masses of early-type stars
A new empirical brightness calibration of early-type stars is presented,entirely based on accurate binary data. This calibration agreesremarkably well with the predictions of the most recent stellar models,but disagrees completely with all other currently used calibrations forearly-type stars. The binaries used to derive the new calibration covera range of masses from about 1.3 solar mass to 25 solar mass,corresponding to a temperature range from 6,700 K to 38,000 K. Over thewhole mass range, no systematic differences between the observed andevolutionary masses were found. The application to the alpha Per clustergives a distance modulus which agrees perfectly with that derived bycomparing its lower main-seqeunce to stars with known parallaxes.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שדרית |
| התרוממות ימנית: | 09h54m33.88s |
| סירוב: | -58°25'16.6" |
| גודל גלוי: | 6.65 |
| מרחק: | 406.504 פארסק |
| תנועה נכונה: | -3.5 |
| תנועה נכונה: | 0.5 |
| B-T magnitude: | 6.435 |
| V-T magnitude: | 6.633 |
קטלוגים וכינוים:
|
INHABITED SKY
