Temperature determination of the Be star from EW ratios. The ratio of the equivalent widths of Mg II over He I lines of the disentangled spectrum (black line) and model spectra of different temperatures and surface gravities (coloured dots, see legend). Shaded regions indicate 1-σ uncertainties. For an estimated value of logg in the range 3.5 to 4.5, the best fit is found for effective temperatures between 16000 and 21000 K.