U. Heiter et al., ABUNDANCE ANALYSIS OF THE LAMBDA-BOOTIS STARS HD-192640, HD-183324 AND HD-84123, Astronomy and astrophysics (Berlin), 335(3), 1998, pp. 1009-1017
The classification of lambda Bootis stars based on photometric indices
or low resolution spectra is not sufficient for a final decision conc
erning a membership to this group. A detailed spectroscopic investigat
ion is necessary to rule out stars with similar classification spectra
but different abundance patterns. Therefore a program on abundance an
alyses of lambda Bootis candidates was established, which makes use of
a software package that enables the analysis of high signal-to-noise
spectra with large resolution. In this paper we present the results of
the application of these tools on two lambda Bootis stars (HD 192640
and HD 183324), for which the derived abundances agree very well with
the literature. For a third star (HD 84123), which shows a very low pr
ojected rotational velocity, the newly determined abundance pattern co
nfirms its membership to the lambda Bootis group. We also investigated
the effect of using several different codes for the calculation of th
e model atmospheres on the synthetic spectra of the program stars, whi
ch span a wide range in effective temperature, gravity and metallicity
. The substitution of opacity distribution functions, which where pret
abulated for metal abundances scaled according to the solar compositio
n, by ones calculated for the individual abundance patterns does not c
hange the synthetic spectra significantly. On the other hand, the deri
ved abundances are sensitive to the treatment of overshooting within t
he calculation of the convective flux for cool stars.