Fast spectroscopic variations on rapidly rotating, cool dwarfs: Pt. 3

We present new time-resolved Hα, Ca II H and K and Mg II h and k spectra of the rapidly rotating K0 dwarf star AB Doradus (=HD 36705). The transient absorption features seen in the Hα line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines-of-sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance-line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. (author)