The abundance pattern of λ Bootis stars^*

Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna and Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215, USA e-mail: ulrike@fafnir.astr.cwru.edu

Corresponding author: heiter@astro.univie.ac.at

Received: 21 July 2001
Accepted: 25 October 2001

Abstract

Within a project to investigate the properties of λ Bootis stars, we report on their abundance pattern. High resolution spectra have been obtained for a total of twelve candidate λ Bootis stars, four of them being contained in spectroscopic binary systems, and detailed abundance analyses have been performed. All program stars show a characteristic λ Bootis abundance pattern (deficient heavy elements and solar abundant light elements) and an enhanced abundance of Na. This work raises the fraction of λ Bootis stars with known abundances to 50%. The resulting abundances complemented by literature data are used to construct a “mean λ Bootis abundance pattern”, which exhibits, apart from general underabundances of heavy elements (≈ -1 dex) and solar abundances of C, N, O, Na and S, a star-to-star scatter which is up to twice as large as for a comparable sample of normal stars.