Astron. Astrophys. 325, 1077-1082 (1997)

2. Observations and data reduction

Spectral observations of 19 ALIVARS have been obtained during 1988-1992 using the spectral complex "Zebra" at the 6-m telescope of SAO RAS. "Zebra" consists of an echelle spectrograph located at the Nasmyth focus, and a quanta-counting system with a frame memory which gives the possibility to control the state of the spectrum being registered (Gazhur et al. 1990). The dispersion spanned a range of 1.2 /pixel (at -line) to 0.6 /pixel (at -line). For control and calibration purposes some MK-standards of different luminosity classes were observed and processed in exactly the same way as the programme stars. The "Journal of observations" is given in Table 1.

Table 1. Journal of observations

The following reductions of the observational material were performed:

1. The spectral sensitivity of the equipment was determined by observing the white dwarfs G 191B2B, HZ 44, Feige 67 and Feige 110 with the known energy distribution in their spectra (Massey et al. 1988) and necessary corrections were introduced.
2. The scattered light was taken into account by introducing an 8% correction.
3. The instrumental profile was determined using argon spectra lines (their own widths are negligible). Averaged profiles ) were drawn for every spectral region from all unblended argon lines. Within the limits of the 5% level of statistical significance, real instrumental profile can be well represented by a Gaussian frequency curve with the parameters a₀ =0, =2.15 pixels.

© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998

helpdesk.link@springer.de