Precision analysis of NGC 2158 with Gaia DR3

Abstract This research uses the third edition of the Gaia Data Release (DR3) to re-investigate the open star cluster NGC 2158. We employed the pyUPMASK Python package and HDBSCAN algorithms to identify the cluster member stars. The key focus of this investigation is our new method of evaluating membership probability based on the radius of each shell in the studied cluster, rather than applying a single probability value to the entire cluster. We calculated all astrophysical parameters of NGC 2158-including center, cluster radius, radial density distribution, color-magnitude diagram, distance, age, and reddening-using the photometric and astrometric data from Gaia DR3. The cluster’s relaxation time, total mass, luminosity, and mass functions are computed. The components of the proper motions ( $$\mu$$ $$_{\alpha }$$ cos $$\delta$$ , $$\mu$$ $$_{\delta }$$ ), and the trigonometric parallax ( $$\varpi$$ ) are found to be $$-$$ 0.196 $$\pm$$ 0.03 , $$-$$ 1.984 $$\pm$$ 0.21 mas/yr and 0.21 $$\pm$$ 0.044 mas, respectively. According to the King model and pyUPMASK membership, we obtained 3067 $$\pm$$ 69.84 stars with a total mass of 3216.4 $$\pm$$ 59.50 $$M_{\odot }$$ . Using the PARSEC stellar isochrones fit, the mean cluster age and its relaxation time are 1.95 $$\pm$$ 0.28 Gyr and 89.0 $$\pm$$ 12.54 Myr, respectively. The cluster distance modulus and reddening are estimated to be 12.86 $$\pm$$ 0.080 , and 0.66 $$\pm$$ 0.040 mag, resulting in a distance of 3.733 $$\pm$$ 0.36 kpc. The mass function MF for the cluster under study has been constructed using a step function with two power lows, $$\alpha _1$$ and $$\alpha _2$$ , rather than the single power low suggested by Salpeter. In this cluster, the $$\alpha _1$$ and $$\alpha _2$$ are found to be $$-$$ 3.2 $$\pm$$ 0.3 and 2.52 $$\pm$$ 0.1 , respectively. The Gaia archive contains 17 stars flagged for variability, detecting 11 stars classified as eclipsing binaries. Additionally, we identified 62 member stars as blue stragglers. We utilized the galpy Python package to obtain the cluster’s kinematics and the Galactic orbital parameters using 126 stars which have radial velocities data in Gaia DR3 archive, with average value 26.1 $$\pm$$ 2.3 km/s.