EX Lupi star
A subclass of eruptive T Tauri stars, also known as EXors or subfuors. EX Lupi stars exhibit optical outbursts of 1–4 mag., each lasting some 10–100 days and separated by several months. They are K or M dwarfs, and at maximum their spectrum is dominated by emission lines similar to those of classical T Tauri stars. As in the case of FU Orionis stars, the eruptions of EX Lupi stars are attributed to an enhanced rate of accretion from a circumstellar disk onto the star's surface.