A type of eruptive variable (often known as a flare star) exhibiting sudden flares with a rise time of seconds to tens of seconds, and decay times of minutes to tens of minutes; abbr. UV. Amplitudes of up to 6 magnitudes have been recorded as in UV Ceti itself, which ranges from 7th to 13th mag. X-ray and radio flares also occur, sometimes coincident with the optical flares. The stars are K–M emission-line dwarfs with very strong magnetic fields, and those in associations are rapidly rotating, young stars. Tidal effects in a binary system may create the strong magnetic fields of other UV Ceti stars. The flare activity is similar to that found on the Sun, but appears more prominent because of the intrinsic faintness of these cool red dwarfs. See also By Draconis star.