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Astron. Astrophys. 318, 819-834 (1997)

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2. Observations

The observations of [FORMULA]  Sco and HD 169454 were carried out at La Silla, Chile, using the ESO 50-cm telescope with our fiber-linked echelle spectrograph [FORMULA]. In 1992 to 1994 we got a sampling rate of one spectrum per day. In 1995 we observed one spectrum every second day with the [FORMULA] upgrade [FORMULA] (see below).

HD 190603 was observed at the Landessternwarte Heidelberg, Germany, Calar Alto Observatory, Spain and the Landessternwarte Tautenburg, Germany, in 1990 and 1991 with the [FORMULA] spectrograph. The planned sampling rate was one spectrum per night for HD 190603. This rate could only be achieved at Calar Alto. At the other sites the sampling rate typically was one spectrum every fourth night. The numbers of spectra and nights of the various campaigns are given in Table 1.


Table 1. The observation campaigns

[FORMULA] covers the wavelength range from 4000 Å to 6740 Å in a single exposure on one CCD (Mandel 1994). The spectral resolving power is [FORMULA].

[FORMULA] (H eidelberg E xtended R ange O ptical S pectrograph) is basically the same instrument with an additional blue channel. A beam splitter is used to divide the light beam into two channels after the echelle grating. Each has its own cross-disperser, camera, and detector. The blue channel covers the range from 3450 Å to 5560 Å, and the red channel from 5820 Å to 8620 Å. The spectral resolving power in both channels is [FORMULA].

The average signal-to-noise ratio in the wavelength range from 5350 Å to 5450 Å is about 110 for the spectra of [FORMULA]  Sco, 100 for HD 169454, and 330 for HD 190603.

The spectra taken at La Silla in the years 1992 to 1994 were published on CD-ROM by Stahl et al. (1995), where the reduction and visualization of the data is described in detail. To represent the large amount of data we display the spectra as dynamical spectra, i.e. time-velocity frames around the rest wavelength of the spectral line. The normalized intensity of the spectra is translated into grey-scales. Black bars mean bigger time gaps, which were not interpolated. Ticks on the right side mark the exposure dates of the original spectra. Above those frames, all spectra are overplotted in the corresponding wavelength range. The cut values applied to the dynamical spectra are indicated by a grey-scale bar on the right. See Fig. 1 for an example of a dynamical spectrum showing the [FORMULA] line of [FORMULA]  Sco in 1992.

[FIGURE] Fig. 1. The dynamical spectrum of [FORMULA]  Sco in [FORMULA] in 1992
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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998