The accretion/diffusion theory for λ Bootis stars in the light of spectroscopic data

¹ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: weiss@astro.univie.ac.at
² Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215, USA
³ Zentraler Informatikdienst der Universität Wien, Universitätsstrasse 7, 1010 Vienna, Austria e-mail: ernst.paunzen@univie.ac.at

Corresponding author: U. Heiter, ulrike@fafnir.astr.cwru.edu

Received: 18 May 2001
Accepted: 25 October 2001

Abstract

Most of the current theories suggest the λ Bootis phenomenon to originate from an interaction between the stellar surface and its local environment. In this paper, we compare the abundance pattern of the λ Bootis stars to that of the interstellar medium and find larger deficiencies for Mg, Si, Mn and Zn than in the interstellar medium. A comparison with metal poor post-AGB stars showing evidence for circumstellar material indicates a similar physical process possibly being at work for some of the λ Bootis stars, but not for all of them. Despite the fact that the number of spectroscopically analysed λ Bootis stars has considerably increased in the past, a test of predicted effects with observations shows current abundance and temperature data to be still controversial.