2018MNRAS.480.1696J

We present Large Binocular Telescope difference imaging data for the final years of four Type II-P/L supernovae progenitors. For all four, we find no significant evidence for stochastic or steady variability in the U, B, V, or R bands. Our limits constrain variability to no more than roughly 5-10per cent of the expected R-band luminosities of the progenitors. These limits are comparable to the observed variability of red supergiants in the Magellanic Clouds. Based on these four events, the probability of a Type II-P/L progenitor having an extended outburst after Oxygen ignition is < 37 per cent at 90 per cent confidence. Our observations cannot exclude short outbursts in which the progenitor returns to within ∼10 per cent of its quiescent flux on the time-scale of months with no dust formation.