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A method of open cluster membership determination
A new method for the determination of open cluster membership based on acumulative effect is proposed. In the field of a plate the relative xand y coordinate positions of each star with respect to all the otherstars are added. The procedure is carried out for two epochst1 and t2 separately, then one sum is subtractedfrom another. For a field star the differences in its relativecoordinate positions of two epochs will be accumulated. For a clusterstar, on the contrary, the changes in relative positions of clustermembers at t1 and t2 will be very small. On thehistogram of sums the cluster stars will gather to the left of thediagram, while the field stars will form a tail to the right. Theprocedure allows us to efficiently discriminate one group from another.The greater the distance between t1 and t2 and themore cluster stars present, the greater is the effect. The accumulationmethod does not require reference stars, determination of centroids andmodelling the distribution of field stars, necessary in traditionalmethods. By the proposed method 240 open clusters have been processed,including stars up to m<13. The membership probabilities have beencalculated and compared to those obtained by the most commonly usedVasilevskis-Sanders method. The similarity of the results acquired thetwo different approaches is satisfactory for the majority of clusters.
| 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 frequency of peculiar A and metallic-line stars in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJ...205..807H&db_key=AST
| The space distribution of M giants in the Warner and Swasey luminosity function field LF 15.
Abstract image available at:http://adsabs.harvard.edu/abs/1974A&AS...15..141S
| The galactic cluster NGC 3228
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..307H&db_key=AST
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Member of following groups:
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Observation and Astrometry data
| Constellation: | Ιστία |
| Right ascension: | 10h22m41.20s |
| Declination: | -51°36'49.5" |
| Apparent magnitude: | 7.896 |
| Distance: | 456.621 parsecs |
| Proper motion RA: | -15.7 |
| Proper motion Dec: | -0.9 |
| B-T magnitude: | 7.811 |
| V-T magnitude: | 7.889 |
Catalogs and designations:
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