The top-left (top-right) frame is the radio data from epoch 1 (epoch 2). The SSA power-law fits of Equation (5) are the continuous curves (see Sections 2 and 3). The bottom frames extrapolate the power-law fit above 3 GHz to lower frequency revealing an excess at 675 MHz. The data in this figure is from Margutti et al. (2018), Troja et al (2018a), and Resmi et al (2018).