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Astron. Astrophys. 364, 646-654 (2000)

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2. The observations

The spectra used in this analysis are from the IUE archives. Two of them (SWP 4284 and LWR 3787), presented in the atlas of Altamore et al. (1992), were recorded in February 1979, when the binary phase, according to Cowley (1965), was 0.24. This means that the hot companion star is at the far side of the M star, but not obscured. We also used IUE spectrum LWP 23 117 above 3100 Å, recorded by De Martino on 17 May 1992. This spectrum is recorded at a different binary phase and shows a smaller shift between the Fe II absorption and emission features.

For the observation at different phases we have only been interested in the wavelength shifts that are due to the relative motion of the stars and not those that are due to the radial velocity of the binary system. The wavelength scale for the observed spectra is therefore calibrated using sharp, apparently unblended, Fe II absorption lines. The Fe II laboratory wavelengths used for the calibration are all from Fourier Transform Spectroscopy (FTS) measurements and are in every case the most accurate value available. Wavelengths given with five decimal places are published in: Nave et al. (1991) for [FORMULA] Å and Nave et al. (1997) for [FORMULA] Å. The remaining Wavelengths are from an unpublished list of preliminary Fe II wavelengths by Johansson.

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001