Journal Article

The anticentre old open clusters Berkeley 27, Berkeley 34 and Berkeley 36: new additions to the BOCCE project<sup>⋆</sup>

P. Donati, A. Bragaglia, M. Cignoni, G. Cocozza and M. Tosi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 2, pages 1132-1148
Published in print August 2012 | ISSN: 0035-8711
Published online August 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21289.x
The anticentre old open clusters Berkeley 27, Berkeley 34 and Berkeley 36: new additions to the BOCCE project⋆

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Abstract

In this paper, we present the investigation of the evolutionary status of three open clusters: Berkeley 27, Berkeley 34 and Berkeley 36, all located in the Galactic anticentre direction. All of them were observed with SUperb Seeing Imager 2 at the New Technology Telescope using the Bessel B, V and I filters. The cluster parameters have been obtained using the synthetic colour–magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMDs with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST). This analysis shows that Berkeley 27 has an age between 1.5 and 1.7 Gyr, a reddening E(BV) in the range 0.40–0.50 and a distance modulus (mM)0 between 13.1 and 13.3; Berkeley 34 is older with an age in the range 2.1–2.5 Gyr, E(BV) between 0.57 and 0.64 and (mM)0 between 14.1 and 14.3; Berkeley 36, with an age between 7.0 and 7.5 Gyr, has a reddening of E(BV) ∼ 0.50 and a distance modulus (mM)0 between 13.1 and 13.2. For all the clusters, our analysis suggests a subsolar metallicity in accord with their position in the outer Galactic disc.

Keywords: Hertzsprung–Russell and colour–magnitude diagrams; Galaxy: disc; open clusters and associations: general; open clusters and associations: individual: Berkeley 27; open clusters and associations: individual: Berkeley 34; open clusters and associations: individual: Berkeley 36

Journal Article.  9409 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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