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

TL;DR

This study measures proper motions and membership probabilities for ~2500 stars in NGC 3766, providing a detailed catalog that aids in understanding the cluster's properties and stellar membership.

Contribution

The paper presents the first extensive proper motion-based membership catalog for NGC 3766, including derived cluster parameters and a publicly available star catalog.

Findings

Membership probabilities identify specific Be and Ap stars as cluster members.

Derived cluster parameters include reddening, distance, age, and mass function slope.

The cluster is found to be dynamically relaxed.

Abstract

Relative proper motions and cluster membership probabilities have been derived for ~ 2500 stars in the field of the open star cluster NGC 3766. The cluster has been observed in $B$ and $V$ broadband filters at two epochs separated by ~ 6 years using a wide-field imager mounted on the WFI@ESO2.2m telescope. All CCD frames were reduced using the astrometric techniques described in Anderson et al. (2006). The proper motion r.m.s. error for stars brighter than $V$ ~ 15 mag is 2.0 mas/yr but it gradually increases up to ~4 mas/yr at $V$ ~20 mag. Using proper motion data, membership probabilities have been derived for the stars in the region of the cluster. They indicate that three Be and one Ap stars are member of the cluster. The reddening $E(B-V)=0.22\pm0.05$ mag, a distance 2.5$\pm$0.5 kpc and an age of ~ 20 Myr are derived using stars of $P_{\mu}>70%$. Mass function slope $x=1.60\pm0.10$ is derived for the cluster and cluster was found to be dynamically relaxed. Finally, we provide positions, calibrated $B$ and $V$ magnitudes, relative proper motions and membership probabilities for the stars in the field of NGC 3766. We have produced a catalog that is electronically available to the astronomical community.