The wavelength calibration was done by taking a ThAr lamp spectrum in conditions identical to the spectrum of IRAS 04553-6825. The average seeing was on both nights. Our echelle spectra resemble the lower resolution spectrum published by Elias et al. I -band magnitude and mag. Van Loon et al.
Flux units are arbitrary.
8183,8195 lines is presented in Fig. Note the perfect match between the spectra taken with a time interval of 3 months or 0.1 in pulsation phase, both between minimum and average light in the K -band. I lines reach their minima in giants, and are larger in both dwarfs and supergiants. Comparison with Schiavon et al. Elias et al.