The Mean Overabundance of Manganese over the Surface of 21 Com from its Midultraviolet Spectra Recorded by IUE

The coaddition of 21 mid ultraviolet spectra of 21 Com taken over the International Ultraviolet Explorer (IUE) mission reveals three strong lines of Mn II at 2576.10, 2593.72 and 2605.68 Å. The synthesis of these lines consistently yields a sizable overabundance of manganese about 10 times the solar manganese abundance. Inspection of the 10 individual spectra taken over the 24 hr monitoring of 21 Com with IUE on 1991 April 17 does not reveal convincing variations of these lines between rotational phases 0.18 and 0.65 of the 2 days period.