Semi-analytical evolution of the first (top panel) and third (bottom panel) binary of tree 197109-HR in the f_GW, p−eccentricity plane. The dashed grey line shows the evolution of the orbital frequency (f_orb), as a way to compare it with f_GW, p. All the data points are colour-coded to indicate elapsed time (from t_0,SAM = 0 to coalescence, for each binary). We use a red cross to highlight when the binaries enter the PTA band (shaded red area).