Open AccessNGC 2587: a sparse open cluster projected on to a populous star field
Author(s) -
Piatti Andrés E.,
Clariá Juan J.,
Ahumada Andrea V.
Publication year - 2009
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2009.15069.x
Subject(s) - physics , astrophysics , open cluster , metallicity , star cluster , photometry (optics) , radius , distance modulus , cluster (spacecraft) , stellar density , star (game theory) , stars , astronomy , computer security , computer science , programming language
We present CCD photometry in the Johnson U , B and V and Kron–Cousins I passbands for the open cluster NGC 2587. The sample consists of 4406 stars reaching down to V ∼ 21.0 . We developed a new method to clean statistically the colour–magnitude diagrams. NGC 2587 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 HD 70927, located close to the cluster centre, seems not to be a member. Our analysis suggests that NGC 2587 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 NGC 2587: μ α =−4.3 ± 3.6 mas yr −1 and μ δ =−2.5 ± 3.4 mas yr −1 . 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. NGC 2587 is located at a distance of (2.70 ± 0.70) kpc from the Sun and ∼9.8 kpc from the Galactic centre.