Eruptive variables are stars varying in brightness because of violent processes and flares occurring in their chromospheres and coronae. The light changes are usually accompanied by shell events or mass outflow in the form of stellar winds of variable intensity and/or by interaction with the surrounding interstellar medium. Among others, T Tauri and R Coronae Borealis stars belong to this group.

T Tauri stars

T Tauri stars are young low mass stars. These stars receive their energy by the contraction of the gas and dust cloud out of which they are formed. The variations in light are irregular and the amplitudes can be as high as 5 magnitudes.

R Coronae Borealis stars (RCB)

This is a rare class of variables. In recent lists of known and suspected RCB stars, one finds only about 40 stars. These stars are normally in their bright state. Without any warning, their brightness can suddenly drop to 8 magnitudes in a few weeks time. They can stay for weeks or even years in this minimum. Rebrightenings are slower and are sometimes interrupted by new minimum state. The unpredictable drops are caused by the formation of dust clouds around the star.