1999A&A...344..211Z

We report HST/HRS observations of gas that appears to have been ejected in the equatorial zone of η Carinae. Some of the observed emission lines are produced by Fe II fluorescence processes, which, for unknown reasons, are uniquely intense near η Carinae. Surprisingly low velocities are found, most likely representing ejection events hundreds of years before the well-known Great Eruption of the 1840's. Alternative interpretations are possible with different geometrical assumptions, but they seem less straightforward and imply a different set of novel problems. The observed velocities less than 100km/s must be hints concerning the physical nature of η Carinae; we propose one speculative scenario, combining the effects of rotation and a modified Eddington limit. The strong fluorescent emission lines occur only in the slowest gas, a result that we cannot yet explain. Altogether, these data pose a number of serious theoretical questions and clues, involving remarkably slow ejection speeds, formation of distinct dense condensations in the ejecta, and peculiarly intense radiative excitation of certain emission lines.