Multi - site observations of surface structures on ABDoradus in 1994 November ?

We present time-resolved optical spectroscopy and broad-band photometry of the rapidly-rotating southern K0 dwarf star AB Doradus, obtained during 1994 November. The data were obtained as part of a collaboration dedicated to MUlti-SIte COntinuous Spectroscopy (MUSICOS), and entailed coordinated observations on three continents to obtain the fullest phase coverage possible subject to limitations of local weather conditions. The Doppler images from the three consecutive nights of the run show excellent mutual agreement, with a dark polar cap and numerous intermediate-and low-latitude features. Simultaneous optical photometry showed numerous short-duration U-band ares, and two longer-duration optical ares with durations of order hours. The latter produced broad-band continuum enhancements throughout the optical spectrum. Where simultaneous spectroscopy was available, both types of are were seen to have counterparts in H and the Ca ii H line. Simultaneous time-resolved ultraviolet spec-troscopy from the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope, reported elsewhere, shows that at least one of the short-duration U-band ares was also observed in C iv with the GHRS. Time-series H spectra showed sig-niicant evolution of the circumstellar prominence system over ve consecutive stellar rotations. One prominence underwent a dramatic increase in distance from the stellar rotation axis. We speculate that this event may have been associated with one of the long-duration ares.