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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Open clusters with Hipparcos. I. Mean astrometric parameters
New memberships, mean parallaxes and proper motions of all 9 openclusters closer than 300 pc (except the Hyades) and 9rich clusters between 300 and 500 pc have been computed using Hipparcosdata. Precisions, ranging from 0.2 to 0.5 mas for parallaxes and 0.1 to0.5 mas/yr for proper motions, are of great interest for calibratingphotometric parallaxes as well as for kinematical studies. Carefulinvestigations of possible biases have been performed and no evidence ofsignificant systematic errors on the mean cluster parallaxes has beenfound. The distances and proper motions of 32 more distant clusters,which may be used statistically, are also indicated. Based onobservations made with the ESA Hipparcos astrometry satellite
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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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The catalogue of equivalent line widths in the spectra of A- and F-stars.
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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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Spectroscopic determination of metallicity in the star-members of young open clusters.
Not Available
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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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Estimation of spectral classifications for bright northern stars with interesting Stromgren indices
The purpose of this investigation is to provide spectroscopic observerswith finding lists of potentially interesting objects. From anunpublished UVBY catalogue of 7026 northern stars (mostly brighter than8.3m) 1094 objects with interesting combinations of UVBY indices havebeen selected. Most stars with post-HD classifications have beenexcluded, as well as late F dwarfs belonging to the intermediatepopulation II. For the 792 remaining stars estimated spectralclassifications are given. The techniques and experience from a previouspaper dealing with southern stars have been utilized here. Among thepredicted spectral classifications are 40 OB stars; 262 Ap, Am, or Fmstars; 16 supergiants of types A to G; 110 bright giants of types A to K(class II); 156 double stars or objects with composite spectra; 26 lateF dwarfs; 91 weak-lined dwarf and giant stars of types F to K, includingearly F-type population II field blue stragglers; and a few possiblefield horizontal branch stars, lambda Bootis-type stars, and late-typehalo giants.
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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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A study of eight galactic clusters from proper motions and photometric characteristics of separate stars.
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A Search for Variables in Galactic Cluster M 39
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A System of Three-Color Photometry, with applications to Galactic Structure in Cygnus
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958AJ.....63..127T&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
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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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Photoelectric Studies.VI. Color-Luminosity Arrays for Stars in Praesepe and in M 39.
Abstract image available at:http://adsabs.harvard.edu/abs/1951ApJ...113..657E
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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
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