Attempts to identify regularity in the unpredictable changes of brightness suggest a period of around 100 days for the small amplitude variations near maximum brightness. At minimum brightness, these microvariations are considered to occur with periods as long as 195 days. The slower variations have been characterised with a period of 6.8 years, with an interval of 35–40 years between deep minima. The microvariations are similar to the brightness changes shown by α Cygni variables, which are less luminous hot supergiants.
