Comparison of the measured (black) and model SEDs for HD 183143. Two model solutions are shown: Application of the CCM extinction law to the ATLAS9 SED with E(B–V) = 1.02 and R_V = 3.8 (dashed blue line) and a modification by employing SKIRT to introduce additional extinction by a PAH component, including secondary emission (red line). With the additional PAH component extinction, values of E(B–V) = 1.22 and R_V = 3.3 are required to obtain a near-perfect fit to the observed SED.