Flare star

A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. The flares occur due to magnetic reconnection in the atmospheres of the stars. The brightness increase is across the spectrum, from X rays to radio waves. Flares can happen once every few days or much less frequently.

Most flare stars are dim red dwarfs. Less massive brown dwarfs might also be capable of flaring. The more massive type RS CVn variables are also known to flare, but it is understood that these flares are induced by a companion star in a binary system which causes the magnetic field to become tangled.