EDP Sciences
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Volume 418, Number 2, May I 2004
Page(s) 539 - 549
Section Galactic structure, stellar clusters and populations
DOI http://dx.doi.org/10.1051/0004-6361:20040043

A&A 418, 539-549 (2004)
DOI: 10.1051/0004-6361:20040043

Membership, rotation, and lithium abundances in the open clusters NGC 2451 A and B

M. Hünsch1, S. Randich2, M. Hempel3, C. Weidner1 and J. H. M. M. Schmitt3

1  Institut für Theoretische Physik und Astrophysik, Universität Kiel, Olshausenstraße 40, 24118 Kiel, Germany
2  INAF-Osservatorio Astrofisico di Arcetri, Largo Fermi 5, 50125 Firenze, Italy
3  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

(Received 19 June 2003 / Accepted 15 January 2004)

High-resolution spectra of 30 late-type and 9 early-type candidate members of the young (~50-80 Myr) open clusters NGC 2451 A and B have been analyzed in order to complement our previous photometric and X-ray study. Cluster membership of these X-ray selected stars has been confirmed or rejected on the basis of radial velocity and H $\alpha$ chromospheric emission. The metallicity of both clusters seems to be about solar - contrary to previous investigations. Lithium abundances have been determined by two different methods, namely curve-of-growth techniques and spectrum synthesis, yielding quite consistent results. The pattern of Li abundances versus effective temperature resembles that of the equally-old Alpha Per cluster, i.e., little Li depletion is seen for solar-type and earlier-type stars, while towards cooler stars Li is more and more depleted, possibly showing a star-to-star scatter below ~ 5200 K. The hottest star in our sample shows a Li abundance ~0.5 dex higher than the meteoritic value. Rotational velocities have been determined in order to investigate the supposed dependence of activity and Li depletion on rotation.

Key words: stars: abundances -- stars: late-type -- stars: rotation -- Galaxy: open clusters and associations: individual: NGC 2451

Offprint request: M. Hünsch, mhuensch@astrophysik.uni-kiel.de

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