Posterior distribution for each of the parameters of the spectral model in Eq. (2), as obtained through the MCMC fitting algorithm for BB data points. The MCMC results illustrated here are for the LR62 region and the multipole bin ℓ = 40–59, one of the two cases shown in Fig. 7. The diagonal shows the probability distribution of each parameter. Median values are A_s = 0.6 ± 0.1, A_d = 137 ± 2, β_s = −3.15 ± 0.17, β_d = 1.50 ± 0.02, and ρ = 0.17 ± 0.04.