Alpha Cygni variables are
variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time others parts expand. They are
supergiant stars of
spectral types B or A. Variations in brightness on the order of 0.1
magnitudes are associated with the pulsations, which often seem
irregular, due to
beating of multiple pulsation periods. The pulsations typically have periods of several days to several weeks.