Variability of η Carinae

Infrared (1.25-3.5 μm) light curves of η Carinae covering the last 20 yr are presented and discussed. Three features are clearly seen in these data. First there is an apparently secular increase in the brightness at the shorter wavelengths (1.25-2 μm), which is also seen in optical data. If this is due to the gradual thinning of dust in the homunculus, then this dust must be predominantly in the form of large grains. Secondly, quasi-periodic variations on a time-scale of about 5 yr are evident. These may be related to the moderate-amplitude variations observed in luminous blue variables. Thirdly, there is evidence for changes on a time-scale of less than 100 d, which are also seen in independent optical photometry. Two possible mechanisms are considered for the quasi-periodic changes: deterministic pulsations and noise-driven pseudo-cyclicity.