Indirect IUE Observations of O VI from Photoexcited Fluorescence Lines of Fe ii, Present in the Spectrum of RR Telescopii

Abstract

A new, highly excited level of Fe II at 13.7 eV has been established by means of six lines in the laboratory spectrum below 2000 Å. Confirming transitions appear in the infrared region. Four of the ultraviolet lines coincide with previously unidentified lines in the IUE spectrum of RR Tel reported by Penston et al. (1983). One of the remaining UV lines coincides with the resonance line of O VI at 1032 Å, outside the range of the IUE. This suggests that the new Fe II level is selectively photoexcited by O VI in RR Tel, resulting in strong fluorescence lines observed. This case of a Bowen mechanism provides an indirect observation of O VI, important for diagnostics of, e.g., symbiotic stars.