Top: wavelet intensity spectrum of monthly averaged S_MWO of κ Ceti. The strongest cycle periods are represented by the darker colours and the dashed horizontal white lines, and the cross-hatched area shows the COI. Bottom: the probability associated with the two detected periods of 5.8 (solid black line) and 3.1 (dotted black line) years. The 90% probability level is shown as a horizontal dashed and dotted line.