A spectroscopic study of the blue halo silicon star HD 97859.

Summary: A study of the atmosphere of the high latitude blue star HD 97859 was carried out using spectrograms at 12.4 A/mm. The results obtained are the follow- wing: a) HD 97859 is probably a field horizontal-branch star with peculiarities characteristic of Ap Si-4200; the spectral type indicated by the color is B 5, b) the atmosphere seems to have a number of areas of enhanced silicon, helium and magnesium. The rotation of the star gives rise to well-marked variations of radial velocities and equivalent widths of the metallic lines, c) several spectrograms present evidence of Fe I lines and of strong unidentified lines. Key words: HD 97859 - silicon halo star - line splitting - Fe ilines