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Astron. Astrophys. 339, 525-530 (1998)

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2. Observations and data reductions

The observations were carried out with the cross-dispersed spectrograph ELODIE (Baranne et al. 1996). This instrument is at the Cassegrain focus of the 1.93 m telescope of the Observatoire de Haute-Provence. The detector was a thinned Tk-CCD, with [FORMULA] elements of size 24 µm2.

The observations were obtained during two nights, namely August 1st and 8th, 1994. The spectral domain ranges from 3900 Å to 6800 Å with a resolving power of 42 000. The typical exposure time was 6 min, leading to a signal-to-noise ratio around 50 for the lines considered in this paper (essentially [FORMULA] 4553 Si iii and H[FORMULA] lines). We reduced the spectra with the INTER-TACOS software (Baranne et al. 1996) that takes care of the offset and flat-field pixel-to-pixel corrections. Finally, the spectra were normalized to the continuum using a cubic spline function and computed in the heliocentric frame.

Approximately, each night represents 1.2 pulsation cycle ([FORMULA] h 50 mn). The pulsation phases [FORMULA] were computed using the ephemeris given by Odell (1994): HJD = 2 447 700.1158 + 0.201044444 d.

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998