1998A&A...335.1009H

The classification of λ Bootis stars based on photometric indices or low resolution spectra is not sufficient for a final decision concerning a membership to this group. A detailed spectroscopic investigation is necessary to rule out stars with similar classification spectra but different abundance patterns. Therefore a program on abundance analyses of λ 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 λ 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 projected rotational velocity, the newly determined abundance pattern confirms its membership to the λ Bootis group. We also investigated the effect of using several different codes for the calculation of the model atmospheres on the synthetic spectra of the program stars, which span a wide range in effective temperature, gravity and metallicity. The substitution of opacity distribution functions, which where pretabulated for metal abundances scaled according to the solar composition, by ones calculated for the individual abundance patterns does not change the synthetic spectra significantly. On the other hand, the derived abundances are sensitive to the treatment of overshooting within the calculation of the convective flux for cool stars.