The binary manganese star Iota Coronae Borealis

Analysis of high dispersion coudé spectrograms shows that the Hg–Mn star ι CrB is a double-lined spectroscopic binary with period 35.47 day and a very small semi-amplitude K = 2.3 km s-1. The secondary star’s lines are visible for those elements in which the primary star is deficient. The mass ratio Mp/Ms = 1.5 ± 0.1. The line-profile asymmetries in ι CrB described by Smith & Parsons are shown to be due to the blending of lines of the two components at the times of their observations. This result casts doubt on the existence of line-profile asymmetries in Hg–Mn stars. Further observations with very high resolution (∼ 5 × 105) are needed in order to check the predictions of Michaud regarding this phenomenon. If Hg–Mn stars are to be studied for this purpose, observers should choose stars known to be single.