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The interacting binary Eta Carinae remains one of the most enigmatic massivestars in our Galaxy despite over four centuries of observations. In this work,its light curve from the ultraviolet to the near-infrared is analysed usingspatially resolved HST observations and intense monitoring at the La PlataObservatory, combined with previously published photometry. We have developed amethod to separate the central stellar object in the ground-based images usingHST photometry and applying it to the more numerous ground-based data, whichsupports the hypothesis that the central source is brightening faster than thealmost-constant Homunculus. After detrending from long-term brightening, thelight curve shows periodic orbital modulation ($\Delta V$ $\sim$ 0.6 mag)attributed to the wind-wind collision cavity as it sweeps around the primarystar and it shows variable projected area to our line-of-sight. Twoquasi-periodic components with time scales of 2-3 and 8-10 yr and lowamplitude, $\Delta V$ $<$ 0.2 mag, are superimposed on the brighteninglight-curve, being the only stellar component of variability found, whichindicates minimal stellar instability. Moreover, the light curve analysis showsno evidence of `shell ejections' at periastron. We propose that the long-termbrightening of the stellar core is due to the dissipation of a dusty clump infront of the central star, which works like a natural coronagraph. Thus, thecentral stars appear to be more stable than previously thought since thedominant variability originates from a changing circumstellar medium. Wepredict that the brightening phase, due mainly to dust dissipation, will becompleted around 2032 $\pm$ 4 yr, when the star will be brighter than in the1600's by up to $\Delta V$ $\sim$ 1 mag.

Distinguishing Circumstellar from Stellar Photometric Variability in Eta Carinae