Abundance analysis of Am binaries and search for tidally driven abundance anomalies - III. HD116657, HD138213, HD155375, HD159560, HD196544 and HD204188

Abstract

We continue here the systematic abundance analysis of a sample of Am binaries in order to search for possible abundance anomalies driven by tidal interaction in these binary systems. New CCD observations of HD116657, HD138213, HD155375, HD159560, HD196544 and HD204188 were obtained in two spectral regions (6400-6500 and 6660-6760Å). A synthetic spectrum analysis was carried out and the basic stellar properties, effective temperatures, gravities, projected rotational velocities, masses, ages and abundances of several elements were determined. We conclude that all six stars are Am stars. These stars were put into the context of other Am binaries with 10 < Porb < 200d, and their abundance anomalies discussed in the context of possible tidal effects. There is a clear anticorrelation of the Am peculiarities with vsini. However, there seems also to be a correlation with the eccentricity and perhaps with the orbital period. The dependence on temperature, age, mass and microturbulence was studied as well. The projected rotational velocities obtained by us were compared with those of Royer et al. and Abt & Morrell.