2 Spectroscopic observations

The observations were performed in August 2000 and September 2001 at the VLT-UT2 with the high-resolution spectrograph UVES (Dekker et al. 2000). The spectrograph settings (dichroic mode, central wavelength 396 nm in the blue arm, and 573 or 850 nm in the red arm) provide almost complete spectral coverage from $\sim$330 to 1000 nm. A 1$\arcsec$ entrance slit yielded a resolving power of $R\sim45~000$.

For CS 22949-037 (V = 14.36) we accumulated a total integration time of 7 hours in the blue, 4 hours in the setting centered at 573 nm, and 3 hours in the setting centered at 850 nm. Table 1 provides the observing log, together with the final S/N obtained at three typical wavelengths, and the barycentric radial velocity of the star at the time of the observation.

The spectra were reduced using the UVES package within MIDAS, which performs bias and inter-order background subtraction (object and flat-field), optimal extraction of the object (above sky, rejecting cosmic ray hits), division by a flat-field frame extracted with the same weighted profile as the object, wavelength calibration and rebinning to a constant wavelength, and step and merging of all overlapping orders. The spectra were then co-added and normalised to unity in the continuum. The mean spectrum from August 2000 has been used for the abundance analysis. The spectrum from September 2001 has a lower S/N ratio, and has been used only to check for radial velocity variations and as a check of the oxygen line profile.

Table 1 gives the barycentric radial velocity for each spectrum of CS 22949-037. The zero-point was derived from the telluric absorption lines (accurate wavelengths of these lines were taken from the GEISA database). The mean value is $V_{\rm r}= -125.64\pm0.12$ km s^-1 (internal error). Note that McWilliam et al. (1995) reported a heliocentric velocity $V_{\rm r}= -126.4\pm0.5$ km s^-1 in 1990, while Norris et al. (2001) obtained $V_{\rm r}= -125.7\pm0.2$ km s^-1 in September 2000. Hence, there is so far no evidence of any significant variation of the radial velocity, and thus no indication that CS 22949-037 might be part of a binary system.