Ultraviolet and Radio Observations of the Young Rapidly Rotating k0 Dwarf Star HD197890

Abstract

We present the results of UV observations taken with the International Ultraviolet Explorer (IUE) satellite and microwave observations obtained with the Australia Telescope during an observing campaign of the rapidly rotating K0 dwarf star III) 197890, nicknamed `Speedy Mic'. This star was recently recognized as a powerful, transient EUV source by the ROSAT WFC, and subsequent investigation showed it to be a ZAMS or possibly a PMS dwarf which may be a member of the Local Association. Our observations show it to have strong, variable UV emission lines near the `saturation' levels. The radio observations show a level of `quiescent' emission consistent with other rapidly rotating stars, but there is no evidence for the large flux variations that normally characterize the time history of such objects.