BY Draconis variables are main-sequence variable stars of late spectral types, usually K or M. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other chromospheric activity. Resultant brightness fluctuations are generally less than 0.5 magnitudes. Light curves from BY Draconis variables are quasiperiodic. The period is close to the star's mean rotational rate. The light curve is irregular over the duration of the period and the light curve changes slightly in shape form one period to the next. For the star BY Draconis the shape of the light curve over a period remained similar for a month.