Harvard College Observatory archival light curve of KT Eri. The black squares indicate B-band magnitudes, the blue triangles upper limits. The red arrows indicate gaps in the coverage that could accommodate an un-detected outburst similar to that in 2009. The length of the arrow tails are proportional to the probability of “missing” an outburst that occurred between two consecutive Harvard plates (length of one magnitude indicates a 100% probability). Left: entire light curve between 1885 and 1965. Right: light curve between 1923.5 and 1954.5. These data show a highly variable progenitor with  ⟨ B ⟩   =  14.7  ±  0.4 (grey dashed line) and a full amplitude variability of around one magnitude. The red triangles show the derived period of 737 days, which coincides with the dips in the light curve.