Transmission spectra for a modeled planet revolving around a G5 star (T_eff = 1300 K, T_int = 200 K, [Fe/H] = 1.0, log(g) = 3.0) with different C/O ratios: (a) C/O = 0.55 (solar), (b) C/O = 0.80, (c) C/O = 1.00, (d) C/O = 1.25, and (e) C/O = 1.50. The blue line indicates the PAH cross section for the abundance obtained from the models for four PAHs together. The red and green lines represent transmission spectra with and without considering PAHs, respectively, in the atmosphere. The gray zones cover the areas with the most important PAH features (represented with the dotted lines) at 3.3 μm and 6–12 μm.