Berkeley 32: A Metal-poor and Dynamically Evolved Open Cluster with Evidence of Radial Migration

Creative Commons License

ÇINAR Ç., Bisht D., Jiang I., Elsanhoury W. H., Belwal K., BİLİR S.

ASTRONOMICAL JOURNAL, vol.172, no.3, 2026 (SCI-Expanded, Scopus)

Abstract

We present a comprehensive chemodynamical analysis of the old, metal-poor open cluster Berkeley 32 based on Gaia DR3 astrometry and Gaia-ESO Survey DR5.1 spectroscopy. Cluster membership is determined using a Gaussian mixture model applied to proper-motion components and trigonometric parallaxes. Isochrone fitting yields an age of 4.9 +/- 0.5 Gyr, a heliocentric distance of 3325 pc, and an extinction of AV = 0.38 +/- 0.12 mag. Spectroscopic member stars exhibit a mean metallicity of [Fe/H] = -0.39 +/- 0.02 dex, near-solar alpha-element abundances, and a weighted mean radial velocity of Vrad = 106.26 +/- 0.03 km s-1. The [Y/Mg] chemical clock yields an age of 4.73 +/- 2.39 Gyr, consistent with the isochrone estimate. Orbital integration indicates a moderately eccentric orbit (e = 0.268 +/- 0.004) with a guiding radius of Rg = 8.82 kpc. The inferred chemical birth radius, Rb = 9.82 kpc, together with Delta R approximate to - 1 kpc, suggests moderate inward radial migration, while the offsets among Rb, Rg, and RGC are consistent with both churning and blurring processes. A photometric analysis identifies a binary fraction of fb = 0.449 +/- 0.017 for systems with mass ratios q >= 0.5, implying a substantial unresolved binary population. Radial cumulative distribution functions further reveal significant mass segregation, with evolved stars more centrally concentrated than main-sequence stars. These results indicate that Berkeley 32 is a dynamically evolved old-disk cluster whose present-day structure and orbit preserve signatures of both internal dynamical evolution and radial migration within the Galactic disk.