The Behavior of Bp He-weak Stars in the Far UV-Paper IX: HD 142990

The analysis of eighteen spectra of the B6 He-weak star HD 142990 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution shortwards of 1700 Å over about 6 hr, ie. about 25% of the rotational period. Several Si II, Si III and Si IV vary consistently. Silicon must be distributed in a non uniform manner over the surface of HD 142990 so as to modulate the FUV flux over the rotational period. The low resolution spectra also confirm this variability.