SCYON Abstract

Received on March 9 2001

Photometric and kinematic studies of open star clusters. III. NGC 4103, NGC 5281, and NGC 4755

AuthorsJörg Sanner1, Jens Brunzendorf2, Jean-Marie Will1, and Michael Geffert1
Affiliation1Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany,
2Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
Accepted byAstronomy & Astrophysics
Links NGC 4103 | NGC 5281 | NGC 4755


We present CCD photometry and proper motion studies of the three open star clusters NGC 4103, NGC 5281, and NGC 4755 (kappa Cru). By fitting isochrones to the colour magnitude diagrams, we found that all three objects are young open star clusters with ages of at most t = 45 Myr. They are located at distances from approx. 1600 pc to 2200 pc, derived from distance moduli (m-M)O ranging from 11 mag to 12 mag. We combined membership determinations based on proper motions and statistical field star subtraction to derive the initial mass function (IMF) of the clusters. The shape of the IMFs could be represented by power laws with exponents of Gamma = -1.46 ± 0.22 for NGC 4103, Gamma = -1.60 ± 0.50 for NGC 5281, and Gamma = -1.68 ± 0.14 for NGC 4755, when - as a reference - Salpeter's (1955) value would be Gamma = -1.35. These results agree well with other IMF studies of open star clusters.