Abstract: The Variability of the HgII 3984 Line of the Mercury-Manganese Star alpha And

The variability of the Hg II 3984 line in the primary of the binary star alpha And was discovered through the examination of high dispersion spectra with S/N ratios greater than 500. This first definitively identified spectrum variation in any Mercury-Manganese star is not due to the orbital motion of the companion. Rather the variation is produced by the combination of the 2.38236 day period of rotation of the primary which we determined and a non-uniform surface distribution of mercury which is concentrated in its equatorial region. If the surface mercury distribution exhibits long term stability, then it is likely a weak magnetic field operates in its atmosphere, but if changes are observed in the line profile over a period of a few years, these would constitute direct evidence for diffusion.