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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Spitzer 24 μm Observations of Open Cluster IC 2391 and Debris Disk Evolution of FGK Stars
We present 24 μm Spitzer MIPS photometric observations of the ~50 Myropen cluster IC 2391. Thirty-four cluster members ranging in spectraltype from B3 to M5 were observed in the central square degree of thecluster. Excesses indicative of debris disks were discovered around oneA star, six FGK stars, and possibly one M dwarf. For the cluster membersobserved to their photospheric limit, we find a debris disk frequency of10+17-3% for B-A stars and31+13-9% for FGK stars using a 15% relative excessthreshold. Relative to a model of decaying excess frequency, thefrequency of debris disks around A-type stars appears marginally low forthe cluster's age while that of FGK stars appears consistent. Scenariosthat may qualitatively explain this result are examined. We concludethat planetesimal activity in the terrestrial region of FGK stars iscommon in the first ~50 Myr and decays on timescales of ~100 Myr.Despite luminosity differences, debris disk evolution does not appear todepend strongly on stellar mass.
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Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
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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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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 Evolution of Stellar Coronae: Initial Results from a ROSAT PSPC Observation of IC 2391
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Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
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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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Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
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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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Radial velocities in the open cluster IC 2391
Radial velocities have been determined for 31 stars in the field of theopen cluster IC 2391, and the percentage of probable radial-velocityvariables is derived. The orbit of one previously known spectroscopicbinary is improved, and the existence of two double-line binaries isconfirmed. The membership to the cluster and the average cluster radialvelocity are discussed and the incidence of short-period binaries amongthe Main-Sequence members of IC 2391 is compared with the incidence forother clusters with similar average axial rotation of its members.
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Chemically peculiar stars in open clusters. I - The catalog
The largest existing compilation is presented of Ap and Am open clusterstars. The catalog contains information on 381 chemically peculiar (CP)stars of the upper main sequence in 79 open clusters. The catalog iscomposed of the following tables: (1) the main body, which lists CP (orsuspected CP) stars which are kinematical (or suspected kinematical)members of open clusters; (2) the list of CP (or suspected CP) starssometimes numbered among cluster members but which are actuallykinematical nonmembers; (3) the list of stars sometimes designated as'peculiar' but, in fact, probably not CP; (4) references for numberingsystems of cluster stars; (5) references for membership; and (6)references for spectral and/or peculiarity types.
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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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Axial rotational velocities in the open cluster IC 2391
Projected rotational velocities have been determined for the members ofthe open cluster IC 2391. The results are discussed in the context ofthe statistical relation between axial rotation and percentage ofbinaries found by Abt (1962) for open clusters and associations.
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Spectral morphology in the open cluster IC 2391
Thirty-one stars brighter than B = 10 in the field of the open clusterIC 2391 are classified on the basis of the mean and MK dispersion. Byusing only normal stars of the main sequence and the absolute visualmagnitudes taken from the calibration made by Garrison (1978), adistance modulus of 5.9 + or - 0.07 (p.e.) magnitudes has been obtainedwhich corresponds to a distance of about 150 pc. A new Am star has beendiscovered, and the presence of two more, discovered earlier, has beenconfirmed. The spectra of the Silicon star HD 74535 and of a Si-Cr-Srobject are characterized.
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Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters
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Six clusters in Puppis-Vela
Intermediate band and H-beta observations of stars in the clusters NGC2451, Cr 140, Cr 135, Cr 173, IC 2391, and Cr 132 in Puppis-Vela arediscussed. Photometric and astrometric parameters for the stars areshown and discussed, along with light and color curves, color-luminosityarrays, histograms for reddening and luminosity, and stellardistributions. Cr 132 consists mainly of members of CMa OB2 plus a fewstars that may be an extension of Cr 140. The latter is an elongatedcluster of some 20 stars, 450 pc distant, 30 million years old, and with(U,V,W) = (+27,-6,-16) km/s. Cr 135 has only eight members, including aK2 Ib star, some 30 million years old, 310 pc distant, and (U,V,W) =(+13,-11,-12) km/s. For NGC 2451, extensive photometry reveals nocluster. Cr 173 is in the Vela sheet and may contain Gamma Vel and thecepheid AH Vel. IC 2391 is a very extended cluster including about twodozen stars brighter than the sun, some 30 million years old and 165 pcdistant, with (U,V,W) = (+20,-19,-3) km/s.
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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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Rotational Velocities in IC 2391
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..940L&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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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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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
