The Fe II emission in the UV spectrum of CH Cyg.

Abstract

Fe II emission lines are present in all UV spectra of CH Cyg, with a great increase in number and intensity since 1985. The authors give a list of emission intensities and equivalent widths for the prominent Fe II lines. Optical depth effects are clearly evident from a comparison of the relative emission intensities within couples of multiplets which share the same upper term. The anomalously high intensity of some emissions seems to be due to a selective fluorescence mechanism originating from Ly α.