The lambda Bootis phenomenon: interaction between a star and a diffuse   interstellar cloud
  The lambda Bootis stars, a group of late B to early F-type population I stars, have surface abundances that resemble the general metal depletion pattern found in the interstellar medium. Inspired by the recent result that the fundamental parameters of these peculiar stars differ in no respect from a comparison sample of normal stars, the hypothesis of an interaction between a star and a diffuse interstellar cloud is considered as a possible explanation of the peculiar abundance pattern. It is found that such a scenario is able to explain the selective accretion of interstellar gas depleted in condensable elements as well as the spectral range of the lambda Bootis phenomenon. 
Inga Kamp (1), Ernst Paunzen (2), ((1) Leiden Observatory, The   Netherlands, (2) Institut fuer Astronomie der Universitaet ...