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

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.