Chemical composition and fundamental parameters of roAp stars

Abstract

Element abundances of three roAp stars, HD 166473, HD 203932, and HD 217522, were determined using Kurucz model atmospheres with metal abundances scaled to solar ones and the results were compared with data from the literature concerning three further roAp stars, normal B and A stars and two lambda Bootis stars. Up to 38 elements could be identified and therefore, this work represents the most complete chemical investigation hitherto published, which can be summarized as follows: - all investigated roAp stars have a similar abundance pattern, - the overabundances of rare earth and other heavy elements are comparable to cool non-pulsating Ap-stars, - iron belongs to the most deficient and cobalt to the most enhanced elements in the group of the iron peak elements, and - the light elements carbon, nitrogen, and oxygen are less abundant than in atmospheres with abundances scaled to the Sun. Beside an unexpected possible relation between effective temperature and metallicity of roAp stars, no outstanding differences from non-pulsating Ap stars could be detected. This statement, however, suffers from the lack of comparably detailed investigations of the latter.