Enhancing SED-based astrometric, photometric, and kinematic studies of SAI 72 and SAI 75 using Gaia DR3

Abstract

This study investigates the open clusters SAI 72 and SAI 75 using Gaia DR3 data, employing the Automated Stellar Cluster Analysis (ASteCA) tool to determine their structural and fundamental properties, including centre coordinates, size, age, distance, mass, luminosity and kinematics. Based on membership probabilities (\(P\ge 50\%\)), we identified 112 and 115 stars as probable members of SAI 72 and SAI 75, respectively. Radial density profile (RDP) analysis yielded cluster radii of 2.35 arcmin for SAI 72 and 2.19 arcmin for SAI 75. The spectral energy distribution (SED) fitting was performed to refine metallicity, distance and colour excess parameters, ensuring consistency within 1\(\sigma \) of isochrone-based estimates. Isochrone fitting of the colour–magnitude diagram (CMD) suggests ages of 316 and 302 Myr, with corresponding distances of \(3160 \pm 80\) and \(3200 \pm 200\) pc. We derived their galactic positions, projected distances \((X_\odot ,Y_\odot )\), and vertical displacements \((Z_\odot )\). Mass function analysis estimates cluster masses of \(612 \pm 174\) M\(_\odot \) for SAI 72 and \(465 \pm 90\) M\(_\odot \) for SAI 75. Kinematic studies indicate that both clusters have reached dynamical equilibrium. The AD diagram method provided convergent point coordinates of \((A,~D)_o = (97^{\circ }.016 \pm 0^{\circ }.09,4^{\circ }.573 \pm 0^{\circ }.05)\) for SAI 72 and \((99^{\circ }.677 \pm 0^{\circ }.10,1^{\circ }.243 \pm 0^{\circ }.09)\) for SAI 75. Orbital analysis confirms that both clusters follow nearly circular trajectories with low eccentricities and minor variations in apogalactic and perigalactic distances. Furthermore, we determine that SAI 72 and SAI 75 originated beyond the solar circle at \(R_{\textrm{Birth}} = 10.825\pm 0.068\) and \(R_{\textrm{Birth}} = 9.583\pm 0.231\) kpc, respectively. Their maximum heights above the galactic plane, \(Z_{\textrm{max}}\) are \(109 \pm 9\) pc for SAI 72 and \(232 \pm 24\) pc for SAI 75, reinforcing their classification as part of the young stellar disc population.