Fast Hα variations on a rapidly rotating, cool main sequence star. Pt. 2

New time-resolved Hα spectra of the rapidly rotating KO dwarf star AB Doradus (=HD 36705) are presented. Thirty per cent of the stellar rotation cycle was observed repeatedly on three of four consecutive nights. The transient absorption features reported in earlier observations of this star are seen to recur at intervals of one stellar rotation cycle where Prot = 0.514 day. This confirms that our earlier interpretation is correct: the absorption features arise in large prominence-like condensations of neutral material, trapped in corotation with the stellar magnetic field. In the new data, clouds are seen to form in a region just outside the Keplerian corotation radius, at the rate of one or two per day. Clouds located further out in the corona are also seen to be moving radially outward from the star at velocities in excess of 30 km s-1. (author)