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Seven-Color Photometry of the Open Cluster NGC 1647 Area
The area of the open cluster NGC 1647 in Taurus is investigated by CCDphotometry in the Vilnius seven-color system. Magnitudes and colorindices are determined for 433 stars down to V = 15.0 mag in the 45arcmin diameter area. For 252 of them photometric spectral andluminosity classes, interstellar reddenings, extinctions and distancesare obtained. According to the CDS WEBDA database, 89 of them have ahigh cluster membership probability. Their mean distance from the Sunis 555±74 pc, excluding four stars which seem to be field stars.The main sequence starts at spectral class B7 V which corresponds to acluster age of about 150 million years. Cluster members show adifferential interstellar extinction ranging from 0.8 to 1.8 mag. Themean extinction of the cluster stars is 1.12±0.25 mag.Interstellar extinction in the area is dominated by the Taurus darkcloud complex at 160 pc. Color excesses of individual stars correlatewell with the 100 μm dust thermal emission intensity. The clustershape is investigated by counting stars down to K=15.6 mag and is foundto be elongated in the direction roughly perpendicular to the Milky Way,with the flattening 0.4.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| 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
| The Hyades: distance, structure, dynamics, and age
{We use absolute trigonometric parallaxes from the Hipparcos Catalogueto determine individual distances to members of the Hyades cluster, fromwhich the 3-dimensional structure of the cluster can be derived.Inertially-referenced proper motions are used to rediscuss distancedeterminations based on convergent-point analyses. A combination ofparallaxes and proper motions from Hipparcos, and radial velocities fromground-based observations, are used to determine the position andvelocity components of candidate members with respect to the clustercentre, providing new information on cluster membership: 13 newcandidate members within 20 pc of the cluster centre have beenidentified. Farther from the cluster centre there is a gradual mergingbetween certain cluster members and field stars, both spatially andkinematically. Within the cluster, the kinematical structure is fullyconsistent with parallel space motion of the component stars with aninternal velocity dispersion of about 0.3 km s(-1) . The spatialstructure and mass segregation are consistent with N-body simulationresults, without the need to invoke expansion, contraction, rotation, orother significant perturbations of the cluster. The quality of theindividual distance determinations permits the cluster zero-age mainsequence to be accurately modelled. The helium abundance for the clusteris determined to be Y =3D 0.26+/-0.02 which, combined with isochronemodelling including convective overshooting, yields a cluster age of625+/-50 Myr. The distance to the observed centre of mass (a conceptmeaningful only in the restricted context of the cluster memberscontained in the Hipparcos Catalogue) is 46.34+/-0.27 pc, correspondingto a distance modulus m-M=3D3.33+/-0.01 mag for the objects within 10 pcof the cluster centre (roughly corresponding to the tidal radius). Thisdistance modulus is close to, but significantly better determined than,that derived from recent high-precision radial velocity studies,somewhat larger than that indicated by recent ground-based trigonometricparallax determinations, and smaller than those found from recentstudies of the cluster convergent point. These discrepancies areinvestigated and explained. } Based on observations made with the ESAHipparcos astrometry satellite. Table~2 is also available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.html
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Galactic clusters with associated Cepheid variables. III - NGC 1647 and SZ Tauri
Observational data and analysis are used to argue that the Cepheid Z Tauis an outlying member of the open cluster NGC 1647. The spatialcoincidence of the Cepheid with the cluster corona, as well ascoincidences in radial velocity, proper motion, and age with clustermembers, present a convincing case for cluster membership, which is alsosupported by independent estimates for the mean radius of SZ Tau. Theevidence presented by the derived luminosity of the Cepheid and itslight curve strongly indicates that SZ Tau is pulsating in the firstovertone, rather than fundamental, mode.
| Radial velocities of stars in open clusters
A CORAVEL type spectrometer was used to measure precise radialvelocities of 116 late-type stars of spectral classes F5 - M5 in thefields of 18 open clusters. Probable cluster members were selected onthe basis of kinematic and photometric data. New or improved radialvelocities for 12 open clusters were thus obtained.
| A radial-velocity survey of the Hyades
Photoelectric radial-velocity measurements, obtained with external erroras small as 0.1 km/s using the 200-inch Hale telescope at PalomarObservatory during the period 1971-1986, are reported for over 400candidate members (with V magnitude between 6 and 14) of the Hyadescluster. The history of Hyades observations is recalled; the Palomarinstrumentation and observing program are described; the data-reductionand standardization procedures are discussed in detail; and the data arepresented in extensive tables and graphs. About 200 of the stars areclassified as cluster members, including 60 spectroscopic binaries.
| Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
| Photometry of Possible Members of the Hyades Cluster - Part Four
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982PASP...94..475W&db_key=AST
| (R-I) colors of cepheids and yellow supergiants in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...203..466S&db_key=AST
| List of errors found in the Yale Zone Catalogues, the GC, and the Cape Photographic Catalogues
Not Available
| Charts for Hyades Stars
Not Available
| Catalogue des étoiles mesurées dans le système photométrique de l'Observatoire de Genève
Not Available
| Distance Moduli of Open Clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965ApJS...12..215H&db_key=AST
| Spectral Classification in Nine Open Clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962ApJ...136..788S&db_key=AST
| Effective wavelengths of 184 stars in the cluster NGC 1647.
Not Available
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