Photometric and spectroscopic study of the intermediate-age open cluster NGC 3960

Abstract

We present charge-coupled device UBVI photometry and high-resolution spectroscopy of the intermediate-age open cluster NGC 3960. The colour-magnitude diagrams (CMDs) derived from the photometric data and interpreted with the synthetic CMD method allow us to estimate the cluster parameters. We derive the following: age τ = 0.9 or 0.6 Gyr (depending on whether or not overshooting from convective regions is included in the adopted stellar models); distance (m - M)0 = 11.6 ± 0.1; reddening E(B - V) = 0.29 ± 0.02; differential reddening ΔE(B - V) = 0.05; and approximate metallicity between solar and half-solar. We obtained high-resolution spectra of three clump stars, and derived an average [Fe/H] = -0.12 (rms 0.04 dex), in very good agreement with the photometric determination. We also obtained the abundances of α-elements, of Fe-peak elements and of Ba. The reddenings towards individual stars derived from the spectroscopic temperatures and the calibrations of Alonso et al. give further support to the existence of significant variations across the cluster. © 2006 RAS.