Research Note

Abundances of a sample of A and F-type dwarf members of the Ursa Major Group

Groupe de Recherches en Astronomie et Astrophysique du Languedoc UMR 5024, Université Montpellier II, Place E. Bataillon, 34095 Montpellier, France e-mail: monier@graal.univ-montp2.fr

Received: 11 April 2005
Accepted: 31 May 2005

Abstract

Abundances of 11 chemical elements have been determined for 10 F and 12 A dwarfs (“normal” and chemically peculiar) bona-fide and probable members of the Ursa Major Group (age about 500 Myr). The abundances were determined in a uniform manner using a model atmosphere analysis by minimising the chi-square of grids of synthetic spectra to observed high resolution high S/N ( and ) spectra obtained in three narrow spectral regions centered around 5075 Å, 5525 Å  and 6160 Å. Specifically, Takeda's (1995) semi-automated procedure was used to derive the abundances of C, O, Na, Mg, Si, Ca, Sc, Fe, Ni, Y, and Ba, the projected rotational velocity and the microturbulent velocity for each star analysed. In graphs [X/H] versus T_eff, the A stars exhibit larger star-to-star variations in [Fe/H], [Ni/H], and [Si/H] than the F dwarfs do. The abundance of nickel is the only one that appears to be correlated with that of iron.