Flux variation gradient diagrams for 2011 (left), 2013 (middle) and 2014 (right) campaigns. The solid lines delineate the bisector regression model yielding the range of the AGN slope. The dashed lines indicate the range of host slopes determined by Sakata et al. (2010) for 11 nearby AGN. The intersection between the host galaxy and AGN slope (red area) gives the host galaxy flux at the time of the campaign in both bands.