Chemical abundance analysis of the open clusters Berkeley 32, NGC 752, Hyades, and Praesepe^{⋆,⋆⋆,⋆⋆⋆}

¹ Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
e-mail: rcarrera@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain
³ INAF - Osservatorio Astronomico di Bologna, Bologna, Italy
⁴ Centro de Investigaciones de Astronomía, Mérida, Venezuela

Received: 14 June 2011
Accepted: 12 August 2011

Abstract

Context. Open clusters are ideal test particles for studying the chemical evolution of the Galactic disc. However, the number and accuracy of existing high-resolution abundance determinations, not only of [Fe/H], but also of other key elements, remains largely insufficient.

Aims. We attempt to increase the number of Galactic open clusters that have high quality abundance determinations, and to gather all the literature determinations published so far.

Methods. Using high-resolution (R  ~  30 000), high-quality (S/N  ≥  60 per pixel), we obtained spectra for twelve stars in four open clusters with the fibre spectrograph FOCES, at the 2.2 Calar Alto Telescope in Spain. We employ a classical equivalent-width analysis to obtain accurate abundances of sixteen elements: Al, Ba, Ca, Co, Cr, Fe, La, Mg, Na, Nd, Ni, Sc, Si, Ti, V, and Y. We derived oxygen abundances by means of spectral synthesis of the 6300 Å forbidden line.

Results. We provide the first determination of abundance ratios other than Fe for NGC 752 giants, and ratios in agreement with the literature for the Hyades, Praesepe, and Be 32. We use a compilation of literature data to study Galactic trends of [Fe/H] and [α/Fe] with Galactocentric radius, age, and height above the Galactic plane. We find no significant trends, but some indication for a flattening of [Fe/H] at large R_gc, and for younger ages in the inner disc. We also detect a possible decrease in [Fe/H] with |z| in the outer disc, and a weak increase in [α/Fe] with R_gc.