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A deep wide-field optical survey in the young open cluster Collinder 359
We present the first deep, optical, wide-field imaging survey of theyoung open cluster Collinder 359, complemented by near-infraredfollow-up observations. This study is part of a large programme aimed atexamining the dependence of the mass function on environment and time.We have surveyed 1.6 square degrees in the cluster, in the I and zfilters, with the CFH12K camera on the Canada-France-Hawaii 3.6-mtelescope down to completeness and detection limits in both filters of22.0 and 24.0 mag, respectively. Based on their location in the optical(I-z, I) colour-magnitude diagram, we have extracted new cluster membercandidates in Collinder 359 spanning 1.3-0.03 Mȯ,assuming an age of 60 Myr and a distance of 450 pc for the cluster. Wehave used the 2MASS database as well as our own near-infrared photometryto examine the membership status of the optically-selected clustercandidates. Comparison of the location of the most massive members inCollinder 359 in a (B-V, V) diagram with theoretical isochrones suggeststhat Collinder 359 is older than α Per but younger than thePleiades. We discuss the possible relationship between Collinder 359 andIC 4665 as both clusters harbour similar parameters, including propermotion, distance, and age.
| A study of the young open cluster Collinder 359
We present the first deep, optical, wide-field imaging survey of theyoung open cluster Collinder 359, complemented by near-infraredfollow-up observations. This study is part of a large programme aimed atexamining the dependence of the mass function on environment and time.We have surveyed 1.6 square degree in the cluster in the I and z filterswith the CFH12K camera on the Canada-France-Hawaii 3.6m telescope downto completeness and detection limits in both filters of 22\fm0 and24\fm0, respectively. Based on their location in the optical (I-z,I)colour-magnitude diagram, we have extracted new cluster membercandidates in Collinder 359 spanning 1.3-0.04 Mȯ,assuming an age of 100 Myr and a distance of 450 pc for the cluster. Wehave used the 2MASS database as well as our own near-infrared photometryto confirm the membership of the optically-selected cluster candidates.Additionally, we have obtained optical spectroscopy and employedchromospheric activity as a further criterion to assess the membershipof candidates.
| 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
| UBVRI photometry of the open cluster Collinder 359, alleged to contain W Ursae Majoris systems
The question of the existence of Cr 359 is addressed. UBV(RI)cphotometry for all 13 stars suggests that nine stars of the originalcluster may form a common main sequence. This may be an indication ofthe physical association of these stars.
| A note on the existence of W UMa-type systems in the cluster CR 359
Arguments are presented that supposedly numerous W UMa-type systems inCr 359 might in fact be field objects with the expected frequency ofoccurrence; in addition four out of the listed nine objects might beeither non-variable or of the RR Lyr-type. The physical association ofstars forming Cr 359 is also questioned but the present data do not makeit possible to disprove it entirely. The far reaching conclusion ofvan't Veer regarding the presence of W UMa systems in very youngclusters finds no support from these results.
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