THE DISCOVERY OF EUV FLARING ACTIVITY IN THE K0V STAR HD-197890 WITH THE ROSAT WIDE-FIELD CAMERA

We announce the detection of flaring activity from a stellar source no t previously known to be coronally active. The source was detected wit h the ROSAT Wide Field Camera during the All Sky Survey stage of the s atellite mission. A long-duration flare lasting for similar to 12000 s was observed with the low-energy survey filter, followed by a period of enhanced activity of about 20 h. Optical observations have identifi ed the source as an active KOV star, HD 197890. Spectral measurements have found CaII emission cole FWHM linewidths corresponding to a rotat ional upsilon sini value of 240 km s(-1), implying that HD 197890 is o ne of the fastest rotating single normal stars known.