Best-fitting hydrostatic MARCS atmospheric spectrum (green solid line) and best-fitting dust-free spectrum of the DMA 1 (red solid line) at bolometric phase φ_bol = 0.59, together with the broadband photometric data (black squares) and ISO/SWS spectrum (black solid line) of RT Vir. The insets present the flux deviation of the hydrostatic MARCS spectrum (green solid line) and the flux deviation of the dust-free spectrum of the DMA 1 (red solid line) from the ISO/SWS spectrum around 3 μm and 4.25 μm, respectively.