2009MNRAS.397.1073P

We present CCD photometry in the Johnson U, B and V and Kron-Cousins I passbands for the open cluster NGC2587. The sample consists of 4406 stars reaching down to V ∼ 21.0. We developed a new method to clean statistically the colour-magnitude diagrams. NGC2587 appears to be a sparse, relatively bright open cluster, with a few tens of members projected on to a populous star field. The comparatively bright F7/8 II type star HD70927, located close to the cluster centre, seems not to be a member. Our analysis suggests that NGC2587 is slightly younger than the Hyades and probably of solar metallicity. A cluster radius of roughly 8 arcmin was estimated from the radial stellar density profile. From 18 probable cluster members with measured proper motions, we derive the following mean values for NGC2587: µ_α= -4.3±3.6mas/yr and µ_δ= -2.5 ±3.4mas/yr. Adopting the theoretical metal content Z = 0.02, which provides the best global fit, we derive a cluster age of 500⁺⁶⁰_–50. Simultaneously, colour excesses E(B - V) = 0.10 and E(V - I) = 0.15 and an apparent distance modulus of V - M_V = 12.50 are obtained. The interstellar extinction in the cluster direction is found to follow the normal law. NGC2587 is located at a distance of (2.70±0.70) kpc from the Sun and ∼9.8 kpc from the Galactic centre.