Zero-Age Main Sequence in the HR Diagram of the Vilnius Photometric System
The zero-age main sequence for solar metallicity stars in the absolutemagnitude vs. color diagram of the Vilnius seven-color photometricsystem is determined. The calibration is based on the results ofphotoelectric photometry of stars in the Hyades, Pleiades and Praesepeopen clusters and the Ori OB1 association. A theoretical Victoria-Reginaisochrone, corresponding to an age of 10 million years, coincides wellwith the lower envelope of the unevolved main sequence.
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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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The Age Range of Hyades Stars
On the basis of canonical models, the age of Hyades supercluster stars,whether in the Hyades and Praesepe clusters or the noncluster field,ranges from (5-6) x 10^8 to 10^9 yr. The difference between the parallaxderived from the supercluster motion and that obtained from Hipparcosobservations has a dispersion only twice that of the mean dispersion ofthe individual Hipparcos values. The supercluster appears not to containred giants on the first ascent of the red giant branch, but onlyasymptotic giant branch (``clump'') stars. The masses obtained forindividual components of binary stars in the supercluster show adispersion of less than 10% when compared with model predictions.
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Evolution of mass segregation in open clusters: some observational evidences
On the basis of the best available member list and duplicityinformation, we have studied the radial structure of Praesepe and of thevery young open cluster NGC 6231. We have found mass segregation amongthe cluster members and between binaries and single stars, which isexplained by the greater average mass of the multiple systems. However,the degree of mass segregation for stars between 1.5 and 2.3 M_sun isless pronounced in Praesepe than in the Pleiades. Furthermore, masssegregation is already present in the very young open cluster NGC 6231although this cluster is likely still not dynamically relaxed. Wediscuss the implications of these results and propose a qualitativescenario for the evolution of mass segregation in open clusters. InPraesepe the mass function of single stars and primaries appears to besignificantly different, like in the Pleiades. We observe an absence ofellipticity of the outer part of Praesepe. Tables 2 and 3 are availableonly in electronic form from the Strasbourg ftp server at 130.79.128.5
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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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High-precision study of proper motions and membership of 924 stars in the central region of Praesepe.
High-precision proper motions for 257 and 296 stars in a 90'x90' regioncentered on BD+20 2170 were obtained from seven plates taken with the40cm refractor (f=6895mm) at Zo-Se station of Shanghai Observatory withsix AC plates and the stellar positions in Russell's (1976) catalogue,respectively. Combining with the data given by Klein-Wassink (1927),Jones (1971), Artyukhina (1971), and Jones & Cudworth (1983), theseproper motions give a sample of 924 stars in the region mentioned above.With membership probabilities estimated by an improved maximumlikelihood method, a very good sample of 198 members is obtained withproper motion accuracies ranging from +/-0.2 to +/-5.0mas/yr, of which60 per cent are better than +/-1.0mas/yr, and the completeness nearlydown to B=15.5.
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Photoelectric Observations in a Wide-Field Area around the Praesepe Cluster
Not Available
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Map-based trigonometric parallaxes of open clusters: The Praesepe
Trigonometric parallaxes for stars in the Praesepe open star cluster arededuced from data collected with the Multichannel Astrometric Photometer(MAP) at the Thaw Refractor of the University of Pittsburgh's AlleghenyObservatory. The weighted mean parallax of five cluster members is +5.21+/- 0.79 mas (0.00079 arcsec), corresponding to a distance modulus of6.42 +/- 0.33 mag. We briefly compare this result with that derivedearlier for the Hyades and note agreement with the distance found bymain-sequence fitting. We also discuss briefly an improvement in theweighting scheme of the centroiding algorithm used in this series.
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ICCD speckle observations of binary stars. IX - A duplicity survey of the Pleiades, Praesepe, and IC 4665 clusters
Multiplicity of stars within clusters is a well-studied phenomenon.However, recent survey work done on the Hyades by Mason et al. (1993)would seem to indicate that even in the most often studied clusters,there may be binaries yet undiscovered. In order to expand the sample ofcluster binaries with potentially short-period visual orbits, a specklesurvey of 45 Pleiades, 54 Praesepe, and 22 IC 4665 bright stars (V isless than 10) for possible multiplicity was conducted at the KPNO 4 mMayall telescope between 1987 October and 1991 November. Of these, threenew binaries have been discovered: one in the Pleiades where the newcomponent may be spectroscopic, another in Praesepe which has beenconfirmed from examinations of archival observations and also has beenresolved by occultation, and the third in IC 4665. Continued study ofthese new binary stars could further refine the cluster distance modulias well as the cluster mass-luminosity relations.
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Washington photometry of open cluster giants - Nine old disk clusters in the third Galactic quadrant
Washington photoelectric photometry for 136 stars in nine old openclusters is presented and used to determine the luminosity class, T(e),and metallicity. The virtually unstudied cluster NGC 2324 is found tohave a metallicity one tenth that of the sun, as is the cluster NGC 2660for which previous estimates have ranged from about +0.1 to -0.5. Athird cluster, NGC 3960, with a Galactocentric distance of only 8 kpc,is found to have a metallicity of -0.7, also substantially lower thanpublished values. Such clusters indicate that substantial scatteractually exists in the tight relation found by Friel and Janes (1992)between the metallicity of an open cluster and its currentGalactocentric distance. Outer disk clusters have a metallicity at agiven age that is much more like that of the LMC counterparts than thatof solar neighborhood disk field stars or clusters.
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Photometry of astrometric reference stars
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference starsis presented. Spectral types and luminosity classifications made fromthe colors are used to determine their spectroscopic parallaxes. In thispaper, colors for 309 stars in 25 regions are given, and classificationsfor 210 stars have been made. These stars form reference frames in theAllegheny Observatory Multichannel Astrometric Photometer astrometricprogram, and in the Praesepe cluster reduced by Russell (1976). It isfound that the present photometric spectral types are reliable to within2.5 spectral subclasses.
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J 2000.0 positions and proper motions of 257 stars in the central part of the Praesepe astrometric standard region
Data are presented on the J2000.0 positions and proper motions of 257stars in the central 1.5 deg x 1.5 deg area of the Praesepe astrometricstandard region. These data obtained with accuracies of 0.005-0.10arcsec for the positions in each direction and 0.0002-0.006 arcsec/yrfor the proper motions in each direction. The list includes stars forwhich proper motions were not given in the Russell (1976) catalog.
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Spectroscopic parallaxes of MAP region stars from UBVRI, DDO, and uvbyH-beta photometry
This paper presents the results of spectral type and luminosityclassification of reference stars in the Allegheny Observatory MAPparallax program, using broadband and intermediate-band photometry. Inaddition to the use of UBVRI and DDO photometric systems, the uvbyH-betaphotometric system was included for classification of blue (B - V lessthan 0.6) reference stars. The stellar classifications made from thephotometry are used to determine spectroscopic parallaxes. Thespectroscopic parallaxes are used in turn to adjust the relativeparallaxes measured with the MAP to absolute parallaxes. A new methodfor dereddening stars using more than one photometric system ispresented. In the process of dereddening, visual extinctions, spectraltypes, and luminosity classes are determined, as well as a measure ofthe goodness of fit. The measure of goodness of fit quantifiesconfidence in the stellar classifications. It is found that the spectraltypes are reliable to within 2.5 spectral subclasses.
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MK classification of the brighter praesepe stars
MK classifications have been obtained for the 42 brightest stars in therich open cluster Praesepe. In the H-R diagram, 10 of the 12 starsbrighter than V = 7.0 mag have luminosity classes brighter than V or areAm stars. Only two of the stars fainter than V = 7.0 mag are ofluminosity class IV. The nine Am stars discovered by Bidelman (1956) areconfirmed. The frequency of these among the late A stars is consistentwith results for field stars, but there is only one Ap star. The reasonsfor that deficiency are discussed.
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Lunar occultations of Praesepe. I - Mauna Kea
Results of lunar occultations of the Praesepe cluster during theDecember 1981 and April 30, 1982 passages as observed from Mauna Keawith the IR telescope facility are reported. Timings of 40 events aregiven. Four Praesepe binaries, previously unknown, were resolved, and anadditional measurement of the occultation-speckle system, 63 Gem, isreported. Two of the Praesepe systems have separations small enough togive hope for spectroscopic resolution.
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A catalogue of stellar spectrophotometric data
A list of 378 sets of stellar energy distributions for 356 stars basedon photoelectric spectrophotometry is presented. Data from eight sourceshave been transformed to the Hayes-Latham calibration of Alpha Lyrae.The procedure follows that of Breger (1976) and the present list extendsprevious data, especially for stars of earliest and intermediatespectral types.
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Energy distributions in main-sequence A and F stars
Scanner observations of A and F main-sequence stars are examined inorder to check whether the observed continuum energy distributions matchscaled Bilderberg models and whether some influence of rotation onconvection can be detected. The continuum energy distributions of A andF field stars and of stars in different clusters with differentrotational velocities are compared; the clusters include the Hyades,Praesepe, Coma, Alpha Persei, and the Pleiades. A comparison withradiative-equilibrium model-atmosphere computations reveals some UV fluxreduction for many stars with B-V greater than 0.14 and a strong UV fluxreduction for all stars with B-V greater than 0.22, regardless ofrotational velocity. The energy distributions are found to match thescaled Bilderberg models, and this is attributed to a reducedtemperature gradient in convectively unstable layers. It is shown thatrotation does not impede convection, but even seems to enhance it,contrary to expectations.
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Scanner observations of main-sequence A and F stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..461B&db_key=AST
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Metallic-Line a Stars and Pulsation
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJ...162..597B&db_key=AST
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Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
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Four-color and H-bet photometry of open clusters. III. Praesepe.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74..818C&db_key=AST
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Effect of rotation on the colors and magnitudes of stars in Praesepe.
Not Available
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Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
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La mesure des vitesses radiales au prisme objectif. XVIII-Classifications spectrales et mesure de vitesses radiales de 112 étoiles situées dans Praesepe
Not Available
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Infrarot-Photometrie der Praesepe. Mit 10 Textabbildungen
Not Available
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Stellar rotation in galactic open clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960MNRAS.121..503T&db_key=AST
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Spectral Classification of the Brighter Stars of the Praesepe Cluster
Not Available
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Praesepe: Magnitudes and Colors.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...116..640J&db_key=AST
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Visuelle und photographische Helligkeiten von 218 Präsepe Sternen
Not Available
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