Proper motions and membership probabilities of stars in the region of open cluster NGC 3766

Abstract

Relative proper motions (PMs) and cluster membership probabilities (Pμ) were derived for ∼2500 stars in the field of the open star cluster NGC 3766. The cluster was observed in theB and V broad-band filters at two epochs separated by ∼6 yr using a wide-field imager mounted onthe WFI@ESO 2.2-m telescope. All CCD frames were reduced using the astrometric techniques described by Anderson et al. The PM rms error for stars brighter than V ∼ 15 mag is 2.0 mas yr-1, but it gradually increases up to ∼4mas yr-1 at V ∼ 20 mag. Using PM data, membership probabilities were derived for the stars in the region of the cluster. They indicate that one Ap and three Be stars are members of the cluster. A reddening of E(B - V) = 0.22±0.05 mag, a distance of 2.5 ± 0.5 kpc and an age of ∼20 Myr were derived using stars with Pμ >70 per cent. A mass function slope of x=1.60±0.10was derived for the cluster, and the clusterwas found to be dynamically relaxed. Finally, we provide positions, calibrated B and V magnitudes, relative PMsand membership probabilities for the stars in the field ofNGC3766. We have produced a catalogue that iselectronically available to the astronomical community. © 2013 TheAuthor. Published by Oxford University Press on behalf of the Royal Astronomical Society.