2. Observations and data reduction
A first snapshot spectrum of HD 192639, covering the wavelength range 4530 - 4720 Å, was taken in July 1995 (JD 2449913.54) with the Carelec spectrograph attached to the 1.93 m telescope of the Observatoire de Haute-Provence. The spectrum was obtained in the second order with a 1200 lines/mm grating blazed at 7500 Å, providing a reciprocal dispersion of 17 Å/mm. The detector was a Tektronix TK512 CCD with a pixel size of m. The spectral resolution as derived from the FWHM of the lines in the NeAr calibration exposures is 1.0 Å.
A more extensive set of spectroscopic observations of HD 192639 was secured during two observing campaigns in August 1996 and July 1997 with the Aurélie spectrograph (Gillet et al. 1994) fed by the 1.52 m telescope of the Observatoire de Haute-Provence. The data were obtained with a 300 lines/mm grating blazed at 6000 Å providing a reciprocal dispersion of 33 Å/mm over a wavelength range from 4100 to 4950 Å. The detector was a Thomson TH7832 linear array with a pixel size of 13 µm. Two spectra were taken in 1996 (JD 2450316.38, 2450318.39), while a total of 25 spectra of HD 192639 were obtained over seven nights in 1997 (JD 2450638.42 - 2450644.60). The mean exposure time was 30 minutes and the mean S/N ratio in the continuum of the raw spectra is 200. Comparison exposures of a ThAr lamp were taken for each stellar spectrum. The spectral resolution as derived from the FWHM of the calibration lines is 1.2 Å.
All the data were reduced in the standard way using the MIDAS software developed at ESO.
The spectra were normalized using properly chosen continuum windows. As for many Of stars, there is a broad emission bump between 4600 and 4700 in the spectrum of HD 192639. The normalized line profiles shown in Figs. 1 and 3 therefore include a weak contribution from this underlying emission feature.
© European Southern Observatory (ESO) 1998
Online publication: June 26, 1998