η Carinae's second eruption and the light curves of the η Carinae variables

Within the general class of highly unstable massive stars called luminous blue variables (LBVs), four stars have experienced "giant eruptions" during which the total luminosities of the stars actually increase. This rare group includes η Carinae, P Cygni, SN 1961v, and V12 in NGC 2403. Several different observations now suggest that some of the material in η Car's equatorial region was probably ejected during its lesser or second eruption around 1890. When the old visual observations are corrected for the probable circumstellar extinction at that time, we find that its 1890 eruption is much more significant in terms of its luminosity, energy, and mass loss than previously assumed and resembles the second peak seen in the historical light curve for P Cyg. The light curves of all four η Carinae variables share a very distinctive appearance with a postmaximum plateau; a second, lesser eruption; and obscuration by circumstellar dust after the giant eruption.