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A&A 429, 607-612 (2005)
DOI: 10.1051/0004-6361:20041458

The old open clusters Berkeley 36, Berkeley 73 and Biurakan 13 (Berkeley 34)

S. Ortolani¹, E. Bica², B. Barbuy³ and M. Zoccali<sup>4

1</sup>  Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
    e-mail: ortolani@pd.astro.it
²  Universidade Federal do Rio Grande do Sul, Dept. de Astronomia, CP 15051, Porto Alegre 91500-970, Brazil
    e-mail: bica@if.ufrgs.br
³  Universidade de São Paulo, Rua do Matão 1226, 05508-900 São Paulo, Brazil
    e-mail: barbuy@astro.iag.usp.br
⁴  Universidad Catolica de Chile, Department of Astronomy & Astrophysics, Casilla 305, Santiago 22, Chile
    e-mail: mzoccali@astro.puc.cl

(Received 12 June 2004 / Accepted 10 August 2004 )

Abstract
BV photometry of the faint open clusters Berkeley 36, Berkeley 73 and Biurakan 13 are studied. For these clusters no colour-magnitude analyses were previously available. The colour-magnitude Diagrams indicate that they are all old open clusters. The derived ages are ~4 Gyr for Berkeley 36, and ~2.3 Gyr for both Berkeley 73 and Biurakan 13. The clusters are not very reddened, with E(B-V) = 0.25, 0.10 and 0.30 respectively for Berkeley 36, Berkeley 73 and Biurakan 13. Berkeley 36 and Berkeley 73 are located at a distance from the Galactic center of ~10 kpc, while Biurakan 13 is much farther, at 15 kpc. A peak in the age distribution appears at 5 Gyr suggesting a distinct star forming event in the disk.

Key words: Galaxy: open clusters and associations: individual: Berkeley 36, Berkeley 73, Biurakan 13 -- stars: Hertzsprung-Russell (HR) and C-M

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© ESO 2004

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