Searching for Variable Stars in the Open Cluster NGC 2355 and Its Surrounding Region

Abstract

We have investigated the variable stars in the field surrounding NGC 2355 based on the time-series photometric observation data. More than 3000 CCD frames were obtained in the V band spread over 13 nights with the Nanshan One-meter Wide-field Telescope. We have detected 88 variable stars, containing 72 new variable stars and 16 known variable stars. By analyzing these light curves, we classified the variable stars as follows: 26 eclipsing binaries, 52 pulsating stars, four rotating variables, and six unclear type-variable stars for which their periods are much longer than the time baseline chosen. Employing Gaia DR2 parallax, kinematics, and photometry, the cluster memberships of these variable stars were also analyzed for NGC 2355. In addition to the 11 variable members reported by Cantat-Gaudin et al. (2018), we identify four more variable member candidates located at the outer region of NGC 2355 and showed homogeneity in space positions and kinematic properties with the cluster members. The main physical parameters of NGC 2355 estimated from the two-color and color–magnitude diagrams are log(age/yr) = 8.9, E(B − V) = 0.24 mag, and [Fe/H] = −0.07 dex.

An Investigation of Open Clusters Berkeley 68 and Stock 20 Using CCD UBV and Gaia DR3 Data

“…In the study, we applied the Unsupervised Photometric Membership Assignment in Stellar Clusters (UPMASK; Krone-Martins & Moitinho 2014) method and used Gaia DR3 astrometric data to calculate membership probabilities (P) of stars in the regions of Berkeley 68 and Stock 20. This method was successfully applied in various earlier studies to identify OC members (Cantat-Gaudin et al 2018Castro-Ginard et al 2018Banks et al 2020;Akbulut et al 2021;Wang et al 2022). UPMASK is based on the k-means clustering method (where k is the number of data clusters), which considers an open stellar cluster as a group of stars that share a similar space in proper-motion components and parallaxes.…”

Investigating kinematics and dynamics of three open clusters towards Galactic anticentre

“…They also found a blue straggler and one unusual straggler star above the main sequence. Wang et al (2022) conducted a time-series study for NGC 2355 and found 88 variable stars in this cluster.…”