2. Observational material
Several B main sequence stars having small projected rotational velocities were selected for analysis. Observations were made with the AURELIE spectrograph (1200 lines grating) on the 1.52-m telescope of Haute Provence Observatoire (France) during January 1999. A linear array detector (Thompson TH 7832) consisting of the 2048 photodiodes was used. Spectral domains were centered on the wavelengths 4700 Å, 5100 Å and 6500 Å. These spectral regions have been selected in order to observe as many C II and N II lines as possible. The resolving power was about 18000. It should be noted that due to excellent weather conditions and extremely good "seeing" during the observations we were able to reach very high S/N ratios for majority of the spectra. Information concerning the program stars and their spectra is given in Table 1. The S/N ratio is the mean value within the order at the continuum level.
Table 1. Program stars and spectra
Preliminary reduction of the spectra (i.e. offset correction, flat-fielding, wavelength calibration) was performed using IHAP package installed at Haute Provence Observatoire. Further work upon the spectra (continuum placement, equivalent width measurement, fragment extraction from the whole spectrum, etc) has been performed with the IBM/PC compatible package DECH20 (Galazutdinov, 1992).
© European Southern Observatory (ESO) 1999
Online publication: October 4, 1999