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Spectroscopic study of the open cluster Blanco 1
Aims: As a part of our program on binaries in open clusters, we presenta spectroscopic study of the bright stars of Blanco 1 aimed at detectingand characterizing spectroscopic binaries. Methods: Forty fivestars previously mentioned as cluster candidates, plus another 24 starsin a wider region around the cluster were observed repeatedly during 6years, with a spectral resolving power 13 300. Radial velocities weremeasured by cross-correlations. Results: We obtained a meancluster velocity of 6.2 ± 0.3 km s-1 and determinedkinematic membership. Eleven spectroscopic binaries were detected, andorbital solutions are presented for eight of them. Six binaries areconfirmed to be members of the cluster. All of them are single-linedspectroscopic systems with periods in the range 1.9-1380 days.Considering all suspected binaries, the cluster binary frequency amountsto about 50%.Based on observations obtained at the Complejo Astronómico ElLeoncito (CASLEO), Argentina.
| 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
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Spectroscopy of the young cluster Blanco 1
We present spectroscopic observations of some 115 stars of the clusterBlanco 1, extending from the Ca II(H,K) region to the Ca II(I-R)triplet, supporting an age similar to that of the young cluster alphaPersei. The H-alpha absorption equivalent with vs (B - V) diagram formsa well-defined locus, with decreasing absorption equivalent width fordecreasing effective temperature, akin to solar neighborhood dwarfs. Alarge spread in the Ca II surface flux, as a function of (B - V), alsoindicates the presence of a high degree of surface inhomogeneity,synonymous with high magnetic activity in young stars. A drop-off in theCa II flux at (B - V) = 1.0 is also similar to the solar neighborhoodstars, and shows that the primary chromospheric cooling changes from theCa II and Mg II lines to the Balmer lines. The mean chromospherictemperature for stars at 4800 K lies between 8000 K and 10,000 K, basedon theoretical models, which is somewhat higher than the older solarneighborhood dwarfs. The high mean Ca II surface flux of the sample isalso consistent with that of other young clusters. We were able tomeasure the equivalent width of the Li(6708) line, whose strength as afunction of (B - V) indicates an age similar to the young cluster alphaPersei. The lithium abundance decreases with decreasing effectivetemperature, consistent with the premise of lithium depletion in starswith larger convection zones. Using published photometry and a recentZero Age Main Sequence (ZAMS) fitting method, we also re-define thedistance to the cluster to be 246 pc.
| UBV and uvby-beta photometry of stars in the region of the Zeta SCULPTORIS cluster
Photoelectric observations of 130 stars in the region of Zeta Sculptorishave been obtained in UBV and uvby-beta. A total of 32 stars areidentified as cluster members, and several other F and G type stars areidentified as probable members. Results indicate an interstellarreddening of E(B-V) = 0.02 mag and that the cluster is slightly metaldeficient.
| Interstellar polarization from observations of A and F stars in high and intermediate galactic latitudes, and from stars in the Mathewson and Ford polarization catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...64..487K&db_key=AST
| Multicolor photometry of the ZET Scl open cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90...81P&db_key=AST
| Visual double stars measured at Las Campanas Observatory, Chile.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..582H&db_key=AST
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