R. Carrera1,2,3,4 and E. Pancino3
Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
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
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 Rgc, 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 Rgc.
Key words: Galaxy: disk / open clusters and associations: individual: NGC 752 / open clusters and associations: individual: Hyades / open clusters and associations: individual: Berkeley 32 / open clusters and associations: individual: Preasepe (M 44) / stars: abundances
Based on observations collected with the fiber spectrograph FOCES at the 2.2 m Calar Alto Telescope. Also based on data from 2MASS survey and the WEBDA, VALD, NIST, and GEISA online database.
Full Table 5 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A30
© ESO, 2011