The variable shell star HR 5999.
Hack, M.; The, P. S.; Tjin A Djie, H. R. E.; Selvelli, P. L.
Netherlands, Italy
Abstract
High and low resolution IUE spectra of the Herbig Ae-type star HR 5999 show strong emission lines of H, O I, C II, C IV, Mg II and possibly C III, N I and O V, and numerous shell absorption lines, mainly of Fe II, Cr II, Mn II and Ni II. The presence of strong emission lines due to hot gas suggests that Hr 5999 has a chromosphere and a corona, probably induced and maintained by a convection zone below the photosphere of this fast rotating (about 180 km/sec) 3 solar mass star. Such emission line spectra are observed for the first time in an A-type star, resembling in strength those of T Tauri stars and late type stars with chromospheres and coronae. These facts confirm the pre-main sequence character of HR 5999.