How many lambda Bootis stars are binaries?

Abstract

In the attempt to shed new light on the lambda Boo phenomenon we analyzed the astrometric, photometric and spectroscopic characteristics of stars out of a list of recently selected lambda Boo candidates. We show that the class is still ill-defined and discuss the possibility that some, if not most stars presently classified as lambda Boo, are in fact binary pairs and that peculiar abundances may not correspond to actual values if the average values of the atmospheric parameters {T_eff} and log g are assumed and the effect of veiling is not taken into account. Partly based on data from the ESA Hipparcos astrometry satellite.