Astron. Astrophys. 317, 178-184 (1997)

2. Observations

High-resolution spectra were recorded with the Coudé spectrograph (CES) of the ESO 1.4 m telescope during two observing runs in 1993 and 1994 (Table 1 ). They were taken with the short camera equipped with ESO CCD #9 (RCA SID 503, pixels) and cover a 70-Å wide spectral band centred at 8665 Å.

The spectrum of a nearby O star was recorded after each programme star to facilitate flatfield correction. The severe interference fringes which show up in the infrared spectral region could be almost totally eliminated in this way.

The very sharp-lined A1V star HR 4138 was used for wavelength calibration. Normalization of the spectra at this point of the data reduction is impossible, because the strong lines of the Paschen series of hydrogen inhibit a correct continuum placement.

Fig. 1. Infrared spectrum of Vega. Solid line: observed spectrum (Babel, private communication). Dashed line: synthetic spectrum calculated with an ATLAS9 (9500, 3.90, -0.5) model atmosphere, theory of ATLAS9 for the Paschen lines. Dashed-dotted line: similar synthetic spectrum but using VCS tables for the Paschen lines. All spectra are normalized to 1.0

© European Southern Observatory (ESO) 1997

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