Illustration of the procedure used to measure the line parameters for a run with L = 0.6L^*. S_tot is the total spectrum in gray, S_BB is the seed blackbody continuum in dashed black, S_tot − S_BB is the residual spectrum in red, and C_poly is the sixth-order polynomial fit of the residual continuum spectrum, excluding the interval around the CRSF (pink shaded region). We measured the line width from the isolated absorption feature (S_tot − S_BB − C_poly); green curve) as the FWHM (blue segment). Likewise, we estimated the centroid energy as the flux-weighted average energy within the region around the minimum where the absorption depth is larger than 90% of the maximum depth (red segment).