Mid-IR spectra of IC 63 and IC 59 observed with the IRS instrument on board Spitzer. The spectra correspond to the SL and LL modules. For IC 63, we have chosen a 15′′ × 15′′ region at the tip of the nebula, along the second front seen in Fig. 4 where the PAH emission is the brightest. However, inspection of the entire data cube shows only small variations in the PAH band ratios throughout the tip of the nebula ( ≲40%). For IC 59, we took the average spectrum over a 25′′× 25′′ region at thetip of the nebula (see Fig. 2). Left panel: both spectra normalized to the peak intensity of the 11.3 μm feature (132.14 MJy sr⁻¹ for IC 63 and9.34 MJy sr⁻¹ for IC 59). Right panel: spectra normalized to the peak intensity of the 11.3 μm feature, after the subtraction of the continuum between 5 and 20 μm.