Rotating Variable Stars

Abstract

There are over 900 stars classified as rotating variables within the General Catalog of Variable Stars. The α2 Canum Venaticorum stars are the most numerous, followed by the BY Draconis variables. Only a dozen or so of the FK Coma Berenices type variables are known. As a group, these variables do not receive a great amount of attention from amateur astronomers, probably because they possess small amplitudes and are almost impossible to accurately observe without the aid of instruments. Generally, the range of brightness between maximum and minimum for rotating variable stars is on the order of hundredths to tenths of a magnitude. On the other hand, when observed with the proper instruments these stars will generally reward the patient observer with rapid amplitude changes (periods) on the order of hours in some cases.

Variable stars with nonuniform surface brightness and/ or ellipsoidal shapes, whose variability is caused by axial rotation with respect to an observer. The nonuniformity of surface brightness distributions may be caused by the presence of spots or by some thermal or chemical inhomogeneity of the atmosphere caused by a magnetic field whose axis is not coincident with the rotation axis.

GCVS