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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New absolute magnitude calibrations for W Ursa Majoris type binaries
Parallaxes of W UMa stars in the Hipparcos catalogue have been analyzed.31 W UMa stars, which have the most accurate parallaxes(σπ/π<0.15) which are neither associated with aphotometric tertiary nor with evidence of a visual companion, wereselected for re-calibrating the Period-Luminosity-Color (PLC) relationof W UMa stars. Using the Lutz-Kelker (LK) bias corrected (mostprobable) parallaxes, periods ({0.26< P< 0.87}, P in days), andcolors ({0.04<(B-V)0<1.28}) of the 31 selected W UMa,the PLC relation have been revised and re-calibrated. The differencebetween the old (revised but not bias corrected) and the new (LK biascorrected) relations are almost negligible in predicting the distancesof W UMa stars up to about 100 pc. But, it increases and may becomeintolerable as distances of stars increase. Additionally, using(J-H)0 and (H-K_s)0 colors from 2MASS (Two MicronAll Sky Survey) data, a PLC relation working with infrared data wasderived. It can be used with infrared colors in the range-0.01<(J-H)0<0.58, and{-0.10<(H-K_s)0<0.18}. Despite of the fact that the2MASS data refer to single epoch observations which are not guaranteedto be taken at maximum brightness of the W UMa stars, the establishedrelation has been found surprisingly consistent and reliable inpredicting LK corrected distances of W UMa stars.
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WIYN open cluster study. XXVI. Improved kinematic membership and spectroscopy of IC 2391
Context: Young open clusters provide important clues to the interfacebetween the main sequence and pre-main-sequence phases of stellarevolution. The young and nearby open cluster IC 2391 is well-suited tostudies of these two evolutionary phases. Aims: We establish a bonafide set of cluster members and then analyze this set in terms of binaryfrequency, projected rotational velocities, [Fe/H], and lithiumabundance. In the wake of the Hipparcos distance controversy for thePleiades, we compare the main-sequence fitting distance modulus to theHipparcos mean parallax for IC 2391. Methods: We have obtained newproper motions for 6991 stars down to V ˜ 13-16 over a~9-deg2 area of the sky comprising IC 2391. The precision ofproper motions, σ_μ=1.7 mas yr-1, allowed us tocalculate reliable membership probabilities. We also obtained preciseradial velocity and v sin i measurements with Coravel and FEROS for 76probable cluster members. The cluster's mean radial velocity is+14.8±0.7 km s-1. The FEROS high-resolution spectrawere used to determine both the [Fe/H] abundance in the four mainsequence dwarfs of IC 2391 and the Li abundance in 47 stars. Inaddition, new BV CCD photometry was obtained for the majority ofprobable cluster members. Results: The proper-motion survey covers a 6times larger sky area than the prior targeted searches for clustermembers in IC 2391. A total of 66 stars are considered bona fide clustermembers down to a mass equivalent to 0.5 Mȯ. A quarterof them have been newly identified with many in the F2-K5 spectralrange, which is crucial for a main-sequence fit. We find a mean [Fe/H]value of +0.06±0.06, when a solar abundance of log ɛ(Fe)= 7.45 is adopted. The main sequence fitting yields a distance modulusthat is 0.19 mag larger than that derived from Hipparcos parallaxes;thus this offset nearly has the size of a similar offset found for thePleiades. The Li abundance pattern is similar to the earlier findingsand is typical for a 40 Myr old open cluster. Conclusions: .A varietyof new data on the probable members of IC 2391 improve essentially allobservational parameters of this young open cluster.
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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.
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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.
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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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Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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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
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True and Possible Contact Binaries in the Hipparcos Catalogue
A comprehensive list of contact binaries included in the HIPPARCOScatalogue is given.
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The Evolution of Rotation and Activity in Young Open Clusters: IC 2391
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..106..489P&db_key=AST
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ICCD Speckle Observations of Binary Stars. XIII. Measurements During 1989- 1994 From the Cerro Tololo 4 M Telescope
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111..936H&db_key=AST
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The Evolution of Stellar Coronae: Initial Results from a ROSAT PSPC Observation of IC 2391
Not Available
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Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
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Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
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Catalog of AP and AM stars in open clusters
The previous results of Raab (1922), Markarian (1951), and Collinder(1931) have been used to catalog Ap and Am stars that are in the fieldof open clusters. Tabular data are presented for the clusterdesignation, the HD or HDE number, the right ascension (1900), thedeclination (1900), and the magnitude. Also listed are the spectraltypes and, for certain stars, the probability of cluster membership.
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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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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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Analysis of the results of MK classification of 176 stars in 37 southern open clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...37..345F&db_key=AST
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Multicolor photometry of metallic-line stars. III. A photometric catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..175M&db_key=AST
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Southern open clusters II. UBV and Hbeta photometry of 11 clusters between galactic longitudes 259d and 280d
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS....9...97V&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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Variation of Metal Abundance in Stars in Population I Clusters
Abstract image available at:http://adsabs.harvard.edu/abs/1971PASP...83..173H
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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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INHABITED SKY
