Abundance analysis of Am binaries and search for tidally driven abundance anomalies – I. HD 33254, HD 178449 and HD 198391.

It is suggested that if the tidally induced meridional circulation of Tassoul & Tassoul existed, it might successfully compete with diffusion processes and rotationally induced meridional circulation. This could affect the chemical composition of an Am binary component. The main goal of this paper is to start a systematic abundance analysis of a sample of Am binaries in order to search for possible observable abundance anomalies driven by tidal interaction in these binary systems. A synthetic spectrum analysis of CCD observations in two spectral regions (6400–6500 and 6660–6760 Å) of HD 33254, HD 178449 and HD 198391 was carried out. Basic stellar properties, atmospheric parameters and abundance patterns were derived. HD 33254 is the star with pronounced Am anomalies, while HD 198391 is found to be an extremely sharp-lined hot Am star. HD 178449 is a controversial and extremely highly rotating star. We have succeeded in detecting a very faint secondary spectrum. The most probable explanation is that we have discovered the new spectroscopic Ab component of this spectroscopic and visual multiple system. [ABSTRACT FROM AUTHOR]