Spectroscopic study of the strontium Am binaries HD 434 and 41 Sex A

Improved spectroscopic orbital elements of the single-line Am binary HD 434 are presented, and cover large gaps in the radial velocity curve obtained earlier by Hube & Gulliver. A substantial deviation of some of the velocities about the computed curve near the ascending node remains unexplained. The MK morphology of the spectrum of HD 434 is examined, and the classification of its metallic line types in the violet and blue regions, along with its revised K- and H-line spectral types, are given for the first time. The strontium anomaly in its spectrum is discussed. 41 Sex A is found to be a prototype of an Am star exhibiting transitional characteristics, forming an evolutionary link between Ap and Am groups of CP stars. Its spectroscopic orbital elements are confirmed using our own velocities. The MK morphology of its spectrum and its spectral line behaviour, especially that of the Sr II 4077 line, are briefly discussed.