a) IRS spectrum of source ID#8. The positions of the C₂H₂ and HCN rovibrational bands are marked. b) IRS spectrum of the source ID#10. The dotted vertical lines mark the features of enstatite. c)–e): The mass absorption coefficients of enstatite and amorphous silicates (with olivine and pyroxene stoichiometry) with grain sizes of 0.1 μm (solid lines), 1.5 μm (dashed lines), and 6.0 μm (dash-dotted lines). The dotted lines in panels b), c) are identical.