Observed spectrum, PD, and PA predicted by retBB for a = 0, M = 21.2 M_⊙, Ṁ = 2.5 × 10¹⁸ g s⁻¹, i = 45° and f_col = 1.5. (a) The red dotted curve shows the spectrum of the direct disk emission. The blue and magenta dashed curves show the elastic reflection of the returning radiation, excluding and including, respectively, the reflection inside ISCO. The spectra include multiple reflections; however, contributions beyond the first order are negligible. The solid black and green curves show the total spectrum without and with reflection inside the ISCO, respectively. (b) and (c) The corresponding PD and PA, the color scheme follows panel (a).