HD 32918 : Ultraviolet spectrum and optical behaviour.

Abstract

The first ultraviolet observations of HD 32918, a southern member of the FK Comae class, are presented. The observations were taken with the IUE satellite at two phases of the optical light curve, with simultaneous photometric coverage over more than one cycle in order to monitor the activity state of the star. The star shows very strong UV emission lines from the chromosphere and transition zone (TZ), similarly to other objects of the same class. Strong variations are seen in the high temperature lines (N V, Si IV, C IV) within one cycle. Similarly to what Bianchi et al.(1985) found for FK Comae, the Mg II (1) emission varies by a large factor on long time-scales (several months).