Lambda Bootis stars in the SuperWASP survey

Abstract

We have analysed around 170 000 individual photometric WASP measurements of 15 well established lambda Bootis stars to search for variability. The lambda Bootis stars are a small group of late-B to early-F, Pop. I, stars that show moderate to extreme (surface) underabundances (up to a factor 100) of most Fe-peak elements, but solar abundances of lighter elements (C, N, O and S). They are excellent laboratories for the study of fundamental astrophysical processes such as diffusion, meridional circulation, stellar winds, and accretion in the presence of pulsation. From the 15 targets, eight are variable and seven are apparently constant with upper limits between 0.8 and 3.0 mmag. We present a detailed time series analysis and a comparison with previously published results. From an asteroseismologic study we conclude that the found chemical peculiarities are most probably restricted to the surface.