Angle- and polarization-averaged emergent spectrum dN/dE as a function of energy E for various transverse Thomson optical depths. The bulk velocity was set to v_ff = 0.05c. The black dashed line represents the seed Bremsstrahlung photon spectrum of temperature kT_e = 10 keV. The solid blue line stands for τ_⊥ = 0.01, the solid gold line is for τ_⊥ = 0.1, and the solid green line refers to τ_⊥ = 1. The vertical blue dotted line indicates the classical cyclotron line energy E_c = 25.55 keV. All spectra are normalized to unity.