Chemical abundances in 43 metal-poor stars

Astrophysics, abstract
astro-ph/0505118

From: Bengt Edvardsson [view email]

Date: Fri, 6 May 2005 10:46:35 GMT   (189kb)

We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni
and Ba for 43 metal-poor field stars in the solar neighbourhood with iron
abundances [Fe/H] ranging from -0.4 to -3.0. Total abundance errors are
estimated to about 0.1-0.2 dex for most elements, while relative abundances are
most probably more accurate. We have made an extensive comparison with other
similar studies and traced the reasons for the, in most cases, relatively small
differences.

Among the results we note the following: We find [O/Fe] from the O I IR-
triplet lines to possibly increase beyond [Fe/H]=-1.0, though considerably less
than obtained by others from abundances based on OH lines. We find correlations
among the deviations for individual stars from the trends of individual alpha
elements relative to Fe. This may support the idea that the formation of the
Halo stars occurred in smaller systems with different star formation rates. We
verify the finding by Gratton et al. (2003b) that stars that do not participate
in the rotation of the galactic disk show a lower mean and larger spread in
[alpha/Fe] than stars participating in the general rotation. The latter stars
also seem to show some correlation between [alpha/Fe] and rotation speed. We
finally advocate that a spectroscopic study of a larger sample of halo stars
with well-defined selection criteria is very important, in addition to the very
considerable efforts that various groups have already made. (Abridged)

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