Investigation of the open star cluster NGC 2323 (M50) based on the proper motions and photometry of its constituent stars

Abstract

The results of a comprehensive study of the Galactic open cluster NGC 2323 (M50) are presented. The positions of stars to a limiting magnitude B ∼ 16 m . 7 in a 42 .5 × 42 .5 area centered on the cluster were measured on six plates from the Pulkovo normal astrograph with a maximum epoch difference of 60 yr. The measurements were performed with the Pulkovo "Fantasy" automated measuring system upgraded in 2010. The corresponding areas from the USNO-A2.0, USNO-B1, and 2MASS catalogues were used as additional plates. As a result, the relative proper motions of stars were obtained with a root-mean-square error of 5.85 mas yr −1 . A catalogue of U BV and JHK magnitudes for objects in the investigated area was compiled from available published resources. The astrometric selection of cluster members was made by the maximum likelihood method. A high individual cluster membership probability of a star (P ≥ 80%) served as the first selection criterion. The position of a star on the photometric colormagnitude (V ∝ (B−V ), J ∝ (J−K)) diagrams of the cluster was considered as the second criterion. The position of an object on the color-color ((U −B)−(B−V ), (J−H)−(J−K)) diagrams served as the third criterion. On the basis of these criteria, it was established that 508 stars are members of NGC 2323. These data were used to refine the physical parameters of the cluster: the mean reddening E(B−V ) = 0 m . 25, the true distance modulus (V − M V ) = 9 m . 85, and the cluster age of about 140 Myr from the grid of isochrones computed by the Padova group for solar chemical composition. Two tables 1 contain the catalogues of proper motions and photometry for stars in the area. The luminosity and mass functions were constructed. The cluster membership of red and blue giants, variable, double, and multiple stars was considered. The position of the cluster center was improved: α = 07 h 02 m 47 s .5, δ = −08 • 20 16 (2000.0).

Photoelectric search for peculiar stars in open clusters

“…There are some recent investigations of NGC 2323 that include photometric but no spectroscopic data (Clariá et al 1998;Sharma et al 2006;Frolov et al 2012). Clariá et al (1998) list E(B − V) = 0.23 mag for W171 which corresponds to the mean value of the cluster (Table 1).…”

Astrometric and photometric study of the open cluster NGC 2323

“…In our study we obtain physical parameters of the cluster by using astrometry and photometry methods. In our calculations we used the data of Frolov et al (2012), which only used photometric analysis to obtain the parameters of NGC 2323 in their study. Before the calculations of astrometric and photometric parameters of NGC 2323 we should check the membership of stars in the cluster, because these parameters depend on membership, except the coordinates of the cluster's center.…”

“…The data for cluster were taken from Frolov et al (2012), who give the positions of stars to a limiting magnitude B ∼ 16.7 mag. An area of 42.5 × 42.5 arcmin 2 centered on the cluster was measured on six plates from the Pulkovo normal astrograph with a maximum epoch difference of 60 yr.…”

“…The total recorded number of stars from the VizieR Online Data Catalog of Frolov et al (2012) is 1103. In our model we treat only 566 stars from this set which have no missing data of their position, proper motion, and the apparent visual magnitudes.…”

“…According to Frolov et al (2012) all, 1103 stars are single, except for three of them, which are the well-known triple system CCDM 07030-0821, the triple system CCDM 07035-0827, and the double star CCDM 07036-0838. Frolov et al (2012) give the values of 9.85 mag and ≈ 1 kpc for the distance modulus and distance, respectively.…”