Fits of four individual lines in the RGS spectrum of λ Cep. For each row, the top panel illustrates the best-fit model convolved with the RGS response and compared with the observed profile. The bottom panel shows the 68.3 (1σ, red continous line), 90 (violet dotted line) and 99% (blue dashed line) confidence contours in the τ_∗ versus R₀ parameter space. The asterisks indicate the best-fit parameters.