Detailed Iron-Peak Element Abundances in Three Very Metal-Poor Stars
  We have obtained new detailed abundances of the Fe-group elements Sc through
Zn (Z=21-30) in three very metal-poor ([Fe/H] $\approx -3$) stars: BD 03 740,
BD -13 3442 and CD -33 1173. High-resolution ultraviolet HST/STIS spectra in
the wavelength range 2300-3050\AA\ were gathered, and complemented by an
assortment of optical echelle spectra. The analysis featured recent laboratory
atomic data for number of neutral and ionized species for all Fe-group elements
except Cu and Zn. A detailed examination of scandium, titanium, and vanadium
abundances in large-sample spectroscopic surveys indicates that they are
positively correlated in stars with [Fe/H]<-$2. The abundances of these
elements in BD 03 740, BD -13 3442 and CD -33 1173 and HD 84937. (studied in a
previous paper of this series) are in accord with these trends and lie at the
high end of the correlations. Six elements have detectable neutral and ionized
features, and generally their abundances are in reasonable agreement. For Cr we
find only minimal abundance disagreement between the neutral (mean of
[Cri/Fe]=+0.01) and ionized species (mean of [Crii/Fe]=+0.08), unlike most
studies in the past. The prominent exception is Co, for which the neutral
species indicates a significant overabundance (mean of [Co/H]=-2.53), while no
such enhancement is seen for the ionized species (mean of [Coii/H]=-2.93).
These new stellar abundances, especially the correlations among Sc, Ti, and V,
suggest that models of element production in early high-mass metal-poor stars
should be revisited.
