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Astron. Astrophys. 354, 193-215 (2000)

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2. The observations

The observations were carried out with the 2.5 m Isaac Newton Telescope at the Roque de los Muchachos Observatory on La Palma during two different observational runs, in 1991 September and 1992 August. We have observed the spectral region between 4000 and 5000 Å, and the region around [FORMULA]. The Intermediate Dispersion Spectrograph was used with the H 2400 B grid in the blue and the H 1800 V grid in the red, attached to the 235 mm camera, which resulted in spectral resolutions of 0.6 and 0.8 Å, respectively, measured on the Cu-Ar arc. The main difference between both runs was the size of the CCD detector, with a larger wavelength coverage per exposure (400 Å instead of 220 Å in the blue) during the second run. Table 1 gives the stellar identification (usually the HD number), star name, OB association to which the star belongs, spectral type and the night in which the stellar spectrum was obtained.


Table 1. Journal of observations. September dates refer to 1991, and August dates to 1992. The night of 9/10 August was dedicated to [FORMULA] observations. All spectral classifications are taken from Walborn (1972, 1973), except that of HD 5 689, which is taken from Garmany & Vacca (1991). Properties indicated in the last column have been taken from Mason et al. (1998)

The reduction of the data was done following standard procedures. We used both IRAF 1and own software developed in IDL. The latter was also used for the spectral analysis. The S/N ratio of the reduced spectra depends on the spectral range, but is usually about 200 in the [FORMULA] region.

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© European Southern Observatory (ESO) 2000

Online publication: January 31, 2000