2017MNRAS.472.3115J

Little is observationally known about the progenitors of Type Ibc supernovae (SNe) or the typical activity of SNe progenitors in their final years. Here, we analyse deep Large Binocular Telescope imaging data spanning the 4 yr before and after the Type Ibc SN 2012fh using difference imaging. We place 1σ upper limits on the detection of the progenitor star at M_U > -3.8, M_B > -3.1, M_V > -3.8 and M_R > -4.0 mag. These limits are the tightest placed on a Type Ibc SN to date and they largely rule out single star evolutionary models in favour of a binary channel as the origin of this SN. We also constrain the activity of the progenitor to be small on an absolute scale, with the RMS UBVR optical variability <= 2500 L_☉ and long-term dimming or brightening trends <= 1000 L_☉ yr^–1 in all four bands.