Quantitative Stellar Spectral Classification. IV. Application to the Open Cluster IC 2391
In this work we perform the first test of a stellar spectralclassification method (Stock & Stock 1999) by applying it to earlytype stars. The sample of stars are the members of the open cluster IC2391 that have high-resolution spectra available in the UVES Project ofParanal Observatory. We show that, in general, absolute magnitudes M_Vand intrinsic colors (B-V)_0 can be recovered within the uncertaintiesstated in the original calibration (˜ 0.4 for the magnitudes and˜ 0.03 for the colors). This accuracy allows us to estimatedistances and to infer membership of individual stars to obtain anaverage distance to the cluster of 156+/-24 pc, which is in goodagreement with previously reported determinations. Finally, we identifyand discuss the real strengths and limitations of this method and wesuggest how it can be improved for future studies.
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Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue
Context: A new reduction of the astrometric data as produced by theHipparcos mission has been published, claiming that the accuracies fornearly all stars brighter than magnitude Hp = 8 are improved, by up to afactor 4, compared to the original catalogue. As correlations betweenthe underlying abscissa residuals have also been reduced by more than anorder of magnitude to an insignificant level, our ability to determinereliable parallaxes and proper motions for open clusters should beimproved. Aims: The new Hipparcos astrometric catalogue is usedto derive mean parallax and proper motion estimates for 20 openclusters. The HR-diagrams of the nearest clusters are compared andcombined to provide future input to sets of observational isochrones. Methods: Three different methods are applied, according to theproximity of the cluster, to compensate, where needed, for projectioneffects, spread in position along the line of sight, and the internalvelocity dispersion of the cluster stars. Results: The newparallaxes have accuracies between 2 and 2.5 times higher than what hadbeen derived from the original Hipparcos catalogue. At least two tothree groups of clusters, mostly of similar ages, are observed to eachoccupy their own specific space in the HR diagram. A significantdiscrepancy in distance moduli from those obtained with isochrone-basedmain-sequence fitting remains, in particular for one of these groups,containing the Pleiades, NGC 2516, and Blanco 1. The difference inabsolute magnitudes between this group and one containing the Hyades andPraesepe clusters appears to be correlated with systematic differencesin the Strömgren ? c0 index between those groups.The same dependency has been known to exist for a long time, and isagain confirmed by the Hipparcos data, in variations in absolutemagnitudes for field stars of the same effective temperature. Conclusions: The positions of the cluster HR diagrams are consistentwithin different groups of clusters shown for example by thenear-perfect alignment of the sequences for the Hyades and Praesepe, forComa Ber and UMa, and for the Pleiades, NGC 2516, and Blanco 1. Thegroups are mutually consistent when systematic differences in ?c0 are taken into account, where the effect of thesedifferences on the absolute magnitudes has been calibrated usingfield-star observations.
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Data mining in the young open cluster IC2391
Large-scale astrometric and photometric data bases have been used tosearch for and confirm stellar membership of the open cluster IC2391.125 stars were found that satisfied criteria for membership based onproper motion components and BRI photometry from the United States NavalObservatory B (USNO-B) catalogue and JHK photometry from the Two MicronAll Sky Survey (2MASS) catalogue. This listing was compared with othersrecently published. A distance to the cluster of 147.7 +/- 5.5 pc wasfound with mean proper motion components, from the Tycho2 catalogue of(-25.04 +/- 1.53 masyr-1+23.19+/-1.23 masyr-1). Arevised Trumpler classification of II3r is suggested. Luminosity andmass functions for the candidate stars were constructed and comparedwith those of field stars and other clusters.
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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
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Seven-Color Photoelectric Photometry of the Omicron Velorum Cluster
Photoelectric observations in the Vilnius seven-color photometric systemof 36 stars in the magnitude range 3.6 < V < 10.7 in the opencluster around the star o Velorum are presented. Photometric spectraland luminosity classes are determined for each star from which the meandistance modulus of the cluster is found to be 5.94+/-0.02 mag and themean color excess EY-V = 0.00+/-0.02 mag. The membership ofthe cluster stars is discussed.
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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.
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The IC 2391 supercluster
Sixty-three field stars and the sparse cluster IC 2391 have beenidentified as members of the IC 2391 supercluster. The members have atleast 95 percent of their space motion, directed toward (A,D) = (5.82h,- 12.44d). Like members of the very similar Pleiades supercluster, theIC 2391 supercluster contains objects of two ages: t = 8 x 19 exp 7 and2.5 x 10 exp 8 yr. A prototype very active chromosphere star and theenigmatic giant variable TZ For are supercluster members together withtwo A-type stars suspected of possessing particulate disks. Anespecially interesting member is the system of Xi Cep (HR 8417) in whichthe two brightest components are greatly undermassive.
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Photoelectric search for CP2-stars in open clusters. VIII - IC 2391 and NGC 2451
Delta-a photometry for 90 stars in the areas of the rather young openclusters IC 2391 and NGC 2451, covering the whole spectral domain ofCP2-stars, is presented. Seven stars show up as photometricallypeculiar, but membership is probable only for 4, 2 for each cluster. NGC2451 may have to be divided into a near and a far cluster. IC 2391 isunreddened and presents itself as ideal reference for the normality linein the Delta-a photometry. Crawford's (1978) calibration yields absolutemagnitudes for the peculiar stars which result in distance moduli veryclose to the mean cluster modulus. Again it is possible to confront thediversity of spectral classifications with the photometric peculiarityindex Delta-a.
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Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
Not Available
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The chemical evolution of the solar neighborhood. I - A bias-free reduction technique and data sample
The possible ways of measuring the age-metallicity relation for thegalactic disk in the neighborhood of the sun are discussed. It is shownthat the use of a field star sample chosen on the basis of effectivetemperature introduces a bias which results in a monotonic increase inthe metal abundance of the disk with time. However, if theage-metallicity relation for the disk can be shown to satisfy certaincriteria, the bias introduced in such a sample can be neglected: thegalactic disk apparently satisfies the criteria. It is concluded that asample analyzed through the use of uvby and H(beta) photometry inconjunction with a self-consistent set of theoretical isochronesprovides the least biased, most accurate estimate of the age-metallicityrelation for the disk.
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Relative radial velocities from objective prism spectra in the region of nine southern open star clusters and a star field at Eta Carinae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..245G&db_key=AST
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Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
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NGC 2516 and the Pleiades Group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...173...63E&db_key=AST
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K-Line Photometry of Stars in Population i Clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJS...23..453H&db_key=AST
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Spectroscopic Studies of Southern Galactic Clusters, I. IC 2391
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969PASP...81..629P&db_key=AST
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Photometric studies of southern galactic cluster. I. IC 2391.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74..899P&db_key=AST
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Stellar spectra in galactic cluster IC 2391
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965MNRAS.129..411B&db_key=AST
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On some southern galactic clusters
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INHABITED SKY
