Rosseland opacity as a function of photon energy in the selected frequency bins with T = 1.5 × 10⁴ K and densities ranging from 2 × 10⁻¹⁶ to 7 × 10⁻¹³ g cm⁻³, taken from the TOPS opacity table assuming solar abundance. The dashed vertical lines mark the frequencies where Lyman, He I, and He II edges are expected to occur. Note that the opacity table reaches floor values for this temperature for densities below 5 × 10⁻¹⁶ g cm⁻³.