2001A&A...374..957S

This is the first of two papers whose main goal is to update and improve the information available on the physical properties of the λ Bootis stars. The determination of the stellar parameters is of fundamental importance to shed light into the different theories proposed to explain the λ Bootis phenomenon. With this aim, projected rotational velocities, effective temperatures, surface gravities and chemical abundances of a sample of suspected λ Bootis stars have been calculated. Five objects showing composite spectra typical of binary systems were found in our analysis. The abundance distribution of the program stars does not resemble the chemical composition of the class prototype, λ Boo, which poses some concerns regarding the idea of a well-defined, chemically homogeneous group of stars. A possible relation between rotational velocities and the λ Bootis phenomenon has been found. This result would be in agreement with the accretion scenario proposed by Turcotte & Charbonneau (1993).