Estimating rotational and macroturbulent line broadening of the stripped star. Comparison between the disentangled spectrum (grey) and a POWR model atmosphere around the Si III 4552 Å line for the narrow-lined stripped star. Shaded regions indicate estimated uncertainties, calculated as the standard deviation of the flux residuals between the observed spectra and the disentangled spectrum. The model spectra were calculated with different values for rotation and macroturbulent velocities that are given in the legend.