A Spectroscopic Search for λ Bootis and Other Peculiar A-Type Stars in Intermediate-Age Open Clusters
As part of our continuing search for peculiar A-type stars, especiallyλ Bootis stars, in open clusters of all ages, we have obtainedclassification spectra of 130 late B, A, and early F-type stars in 12intermediate-age open clusters, including NGC 1039, 2281, 2548, 6633,7039, 7063, 7092, and 7209, IC 4665, IC 4756, Stock 2, and Praesepe. Thespectra were obtained with resolutions of 1.8 and 3.6 Å on the 0.8m telescope of Appalachian State University and were classified on theMK system. Numerous classical Ap and Am stars were found among the 130,including two new Ap stars in NGC 7092. In addition, three emission-linestars and two candidate λ Bootis stars were found. Neither ofthese λ Bootis candidates turned out to be members of theirrespective clusters. Combined with 184 stars previously classified in 10other intermediate-age open clusters, also devoid of λ Bootisstars, a statistically significant null result is obtained. We discussthe implications of this null result for our understanding of theλ Bootis mechanism.
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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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Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
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Spectrophotometry of 237 Stars in 7 Open Clusters
Spectrophotometry is presented for 237 stars in 7 nearby open clusters:Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, andM39. The observations were taken by Lee McDonald and David Bursteinusing the Wampler single-channel scanner on the Crossley 0.9m telescopeat Lick Observatory from July 1973 through December 1974. Sixteenbandpasses spanning the spectral range 3500 Angstroms to 7780 Angstromswere observed for each star, with bandwidths 32Angstroms, 48 Angstromsor 64 Angstroms. Data are standardized to the Hayes-Latham system tomutual accuracy of 0.016 mag per passband. The accuracy of thespectrophotometry is assessed in three ways on a star-by-star basis.First, comparisons are made with previously published spectrophotometryfor 19 stars observed in common. Second, (B-V) colors and uvby colorsare compared for 236 stars and 221 stars, respectively. Finally,comparsions are made for 200 main sequence stars to the spectralsynthesis models of Kurucz, fixing log g = 4.0 and [Fe/H] = 0.0, andonly varying effective temperature. The accuracy of tests using uvbycolors and the Kurucz models are shown to track each other closely,yielding an accuracy estimate (1 sigma ) of 0.01 mag for the 13 colorsformed from bandpasses longward of the Balmer jump, and 0.02 mag for the3 colors formed from the three bandpasses below the Balmer jump. Incontrast, larger scatter is found relative to the previously publishedspectrophotometry of Bohm-Vitense & Johnson (16 stars in common) andGunn & Stryker (3 stars). We also show that the scatter in the fitsof the spectrophotometric colors and the uvby filter colors is areasonable way to identify the observations of which specific stars areaccurate to 1 sigma , 2 sigma , .... As such, the residuals from boththe filter color fits and the Kurucz model fits are tabulated for eachstar where it was possible to make a comparison, so users of these datacan choose stars according to the accuracy of the data that isappropriate to their needs. The very good agreement between the modelsand these data verifies the accuracy of these data, and also verifiesthe usefulness of the Kurucz models to define spectrophotometry forstars in this temperature range (>5000 K). These data define accuratespectrophotometry of bright, open cluster stars that can be used as asecondary flux calibration for CCD-based spectrophotometric surveys.
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Catalogue of proper motions, UBV-photometry and spectral classification in the region of NGC 7092 (M39)
Not Available
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Absolute proper motions of the open clusters M 39 and TR 37
The absolute proper motions of five BD stars in the region of the opencluster M 39 and of 20 BD stars in the region of the open cluster Tr 37are determined with an accuracy of 0.26 arcsec/100 yr. Measurements ofthe proper motions of the open clusters M 39 and Tr 37 are reported.
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Infrared photometry of upper main sequence stars in M39
Infrared photometry of 19 Main sequence stars in the open cluster M39 ispresented. Infrared-infrared and optical-infrared color-color andcolor-magnitude diagrams are presented and compared with mean intrinsiccolor for Population I stars. An interstellar reddening of E(B - V) =0.01 is obtained by analysis of the color-color diagrams. Comparisonwith a set of theoretical isochrones leads to an age estimate for thecluster between 240 and 480 million years.
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Third preliminary catalogue of stars observed with the photoelectric astrolabe of the Beijing Astronomical Observatory.
Not Available
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A photometric study of the open cluster M39
Photoelectric UBV magnitudes of 50 stars in the field of M39 have beenobtained for most of which previous photoelectric data were notavailable. These include 36 new members given by Platais (1984). Thereddening for the cluster has been found to be 0.03 mag. A distance of300 pc has been estimated for the cluster. The age of the cluster liesbetween 200 million and 400 million yr.
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Galactic cluster star radial velocities obtained with a focal reducer field spectrograph. I - The clusters IC 1805, NGC 2287, NGC 2548, IC 4665, NGC 6633, NGC 6940 and NGC 7092
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...62..301G&db_key=AST
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New candidate members of the open cluster NGC 7092 (M39)
Proper-motion and UBV data on 7931 stars in the 110-arcmin-diameterfield of the open cluster NGC 7092 from the catalog of Platais (1983)are analyzed, and the results are presented in tables and a graph. Atotal of 38 stars previously identified as cluster candidates areconfirmed, and 43 new candidates are presented. Of the members andcandidates, 38 have B magnitude 6-11 mag; 34 have 11.0-14.8 mag; and 9have 14.8-16.7 mag.
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Evidence of decay of the magnetic fields of AP stars
Data obtained in the Geneva photometric system (Rufener, 1981) andappropriate calibrations of this system in terms of surface magneticfield and gravity are used to provide, on the basis of 708 field andcluster Ap stars, observational evidence that these stars undergo decayof their magnetic field on an evolutionary timescale. Justifications aregiven for the application of a photometric gravity calibration topeculiar stars. The dependence of the photometrically estimated surfacemagnetic field on gravity is found to differ markedly from availabletheoretical calculations. HgMn stars are found to show the same trend,strengthening the impression that they might be slightly magnetic.He-weak stars do not.
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The Sirius group as a moving supercluster
Without use of trigonometric parallaxes, the distances of some 50 brightstars have been determined on the basis of their well-determined propermotions and membership in a supercluster that includes Sirius. Theastrometric parallaxes are in excellent agreement with those obtainedfrom photometric parameters and, for the stars within 40 pc of the sun,they are also in agreement with trigonometric determinations. Thesupercluster stars are near 2.4 x 10 to the 8th yr old with (Fe/H) near-0.1. The resulting color-luminosity array confirms the expectedmain-sequence displacement for stars with a metal abundance only abouttwo thirds that of the Hyades supercluster members. The superclustercontains the UMa cluster and M39 (NGC 7092) but the former, at least,has only attracted attention because of the concentration of a fewbright (Dipper) supercluster members in Ursa Major.
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Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
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Membership of M39
Proper motions are presented for 1710 stars in the vicinity of M39. Only30 of these stars are suggested to be cluster members. The cluster isunusual both for its sparseness and its lack of a faint stellarpopulation. The cluster distance is redetermined and found to be 265 pc,and its age is estimated as 780 million years.
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Spectral types in the open cluster M 39.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..222A&db_key=AST
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A spectroscopic study of the open cluster M39.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...186..177A&db_key=AST
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Narrow-band photometry of early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&A....12....5H&db_key=AST
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Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
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A study of eight galactic clusters from proper motions and photometric characteristics of separate stars.
Not Available
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Rotational Velocities of Stars in M39 and the Ursa Major Cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...133..907M&db_key=AST
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Distribution of the nearer bright stars in the color-luminosity array.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957AJ.....62...45E&db_key=AST
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The color-luminosity array for some galactic clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955AJ.....60..407E&db_key=AST
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Drei-Farben-Photometrie von 11 offenen Sternhaufen, insbesondere solchen mit O-und frühen B-Sternen. Mit 21 Text-abbildungen
Not Available
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Magnitude, Color, and Spectral-Type Relations in the Galactic Cluster M 39.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1953ApJ...117..366W&db_key=AST
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Magnitudes, Colors, and Spectral Types in M 39.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1953ApJ...117..353J&db_key=AST
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Proper Motions in the Galactic Cluster Messier 39.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1940ApJ....92..434E&db_key=AST
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Untersuchungen der offenen Sternhaufen NGC 7092 (M 39), NGC 7209, und NCG [sic] 7243
Not Available
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