|Mass function of open clusters NGC 1857 and Czernik 25|
The first CCD photometric UBVRI observations of the open clusters NGC1857 (Czernik 20, OCl 427) and Czernik 25 (OCl 493) are presented. Theobservations were obtained on 28 November 2003 with the 2m HimalayanChandra Telescope at Hanle using a LN2 cooled 2k ×2k CCD. Thecolour excess E(B-V) is found to be non-uniform in the line of sight ofNGC 1857 ranging between 0.38 and 0.60 mag, while it is 0.69 mag for Cz25. Further, the clusters NGC 1857 and Cz 25 are estimated to be at adistance of 5.75±0.8 kpc and 4.79±0.5 kpc respectively. Asthe log (age) of NGC 1857 is estimated to be in the range of 8.00 to8.25 and that of Cz 25 is 8.45, they may be considered to be ofintermediate age. The luminosity function (LF) and the mass function(MF) for both the clusters have been derived. The MF slopes for theclusters NGC 1857 and Cz 25 are -2.39±0.26 and -2.70±0.25respectively. These values are in fair agreement with that given bySalpeter. Mass segregation is observed in both the clusters and it couldbe due to the dynamical evolution of the clusters or the imprint of starformation process or both.
|Collaborative Research of Open Star Clusters|
Preliminary results on observations of open clusters are pre-sented. Theproject has been initiated in the framework of the Uzbek-Taiwan andTaiwan-Baltic collaboration, mainly to upgrade and make use offacilities at Maidanak Observatory. We present detailed,multi-wavelength studies of the young cluster NGC 6823 and theassociated complex nebulosity, to diagnose the young stellar populationand star formation history in the region. In addition, 7 compact openclusters have been monitored for stellar variability. We show howobservations like these could feasibly be used to look for exoplanettransit events. We also expect to join the Whole-Earth Telescope effortin future campaigns for asteroseismology.
|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 (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|CCD Photometry of the Open Cluster NGC 1857|
We present a new CCD photometry in the BVRI system of the open clusterNGC 1857, a largely unstudied cluster located in the galacticanticenter. Presented are results obtained using both IRAF/APPHOT andDAOPHOT to reduce multiple datasets obtained with the UAO 61-inchtelescope, Mt. Bigelow, Arizona. The resulting color-magnitude diagramsshow a well-defined sequence from the turnoff, near V = 13.3 and B - V =0.55 to V~17, and present several giant candidates. Fitting oftheoretical isochrones allows numerical estimates of the log(Age) =(8.25 +/- 0.3) and E(B-V) = (0.68 +/- 0.05).
|Formation and evolutionary properties of the Galactic open cluster system|
Results are reported from a statistical analysis of observational dataon 100 open clusters within 2 kpc of the sun, selected from the catalogof Lynga (1987). The selection criteria and the completeness of thesample are discussed; the data are compiled in a table; and the analysisresults are presented in a series of graphs and characterized in detail.A cluster formation rate of 0.45 clusters/kpc Myr is found,significantly lower than the rates determined previously (using clusterswithin 1 kpc of the sun) and corresponding to a cluster star-formationefficiency of 0.0063. The low average cluster lifetime (about 10 Myr)suggests that clusters are formed as unstable systems.
|Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)|
|Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters|
|Dreifarbenphotometrie in offenen Sternhaufen sowie in zwei Sternfeldern im Cyg.|
|Variable stars in open clusters.|
|Red indices in galactic clusters|