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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
| The nature of some doubtful open clusters as revealed by HIPPARCOS
We discuss the nature of some galactic open clusters by using propermotions and parallaxes from the Hipparcos and ACT catalogues. We showthat the clusters Collinder 399, Upgren 1, NGC 1252 and Melotte 227 donot exist. Collinder 132 is found to be mainly composed out of membersof an OB association, but there may be a star cluster present in thisarea too. Roeser & Bastian (1994) proposed that NGC 2451 consists oftwo star clusters. We show that NGC 2451 A definitively does exist, NGC2451 B may exist. A star cluster may also be present in the area ofRoslund 5. The Hipparcos data finally confirm the reality of Collinder135.
| Radial velocities in the region of CR 135
We give mean radial velocities of 63 stars belonging to a 2 deg x 2 degfield centered on Cr 135 in Puppis, where only a few radial velocitiesof bright stars are at present known. We obtained relative radialvelocities which have been fitted to the IAU standard system of radialvelocities by means of some stars with already known radial velocities.We present the histogram of the errors and a general radial-velocitydiagram, as well as a discussion about the possible variable stars andthe cluster membership. The histogram of the errors shows a maximumbetween E = 2.0 and E = 3.0 km/s for an average of six plates per star.The general radial-velocity diagram has a peak at about 20 km/srepresenting principally the field stars. The radial velocities of thefive brightest stars and those of stars previously selected as probablecluster members lie in this peak. On the basis of photometric data, thephysical reality of Cr 135 has been contested. Our results show that if,nevertheless, the cluster exists, its radial velocity is very close tothat of field stars. Cr 135 could also belong to an old association orto a stellar group.
| Six clusters in Puppis-Vela
Intermediate band and H-beta observations of stars in the clusters NGC2451, Cr 140, Cr 135, Cr 173, IC 2391, and Cr 132 in Puppis-Vela arediscussed. Photometric and astrometric parameters for the stars areshown and discussed, along with light and color curves, color-luminosityarrays, histograms for reddening and luminosity, and stellardistributions. Cr 132 consists mainly of members of CMa OB2 plus a fewstars that may be an extension of Cr 140. The latter is an elongatedcluster of some 20 stars, 450 pc distant, 30 million years old, and with(U,V,W) = (+27,-6,-16) km/s. Cr 135 has only eight members, including aK2 Ib star, some 30 million years old, 310 pc distant, and (U,V,W) =(+13,-11,-12) km/s. For NGC 2451, extensive photometry reveals nocluster. Cr 173 is in the Vela sheet and may contain Gamma Vel and thecepheid AH Vel. IC 2391 is a very extended cluster including about twodozen stars brighter than the sun, some 30 million years old and 165 pcdistant, with (U,V,W) = (+20,-19,-3) km/s.
| Wide- and narrow-band photometry of stars in a field around Collinder 135
A field of about 10,000 square arcmin around the cluster Cr 135 isstudied using UBV, H-alpha, and H-beta photometries. The photometricdata do not favor the existence of Cr 135 as a real open cluster. Onlyeight B-type stars lie on a very well-defined main sequence in the UBVphotometric diagrams. These eight stars - which are shown not to begravitationally bound - are located at a mean distance of 630 pc with aforeground color excess amounting to E(B-V) equals 0.06 magnitudes.These stars, together with most of the B stars in the region, can beconsidered probable members of the large, old, Pup-Can association.
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