3 Observations and data reduction

3.1 WHT/UES observations

Stars 6 and C were observed with the William Herschel Telescope (WHT) at La Palma, Canary Islands on the nights February 10 and 11, 2000, using the Utrecht Echelle spectrograph (UES). With a slit width of 1.1$\arcsec$, the 31 mm^-1 grating and the SiTe1 2048$\times$2048 24 $\mu$m pixel CCD as detector, the resultant wavelength coverage was $\sim$ 3820 - 7000 Å at $R\equiv\lambda/\Delta\lambda = 50~000$. In spite of over 9 hours of on-star integration for Star 6, the signal-to-noise ratio nowhere exceeded 10, even in the peaks of the best orders. However, for Star C, a total integration time of 9000 s (in 1800 s exposures) yielded a peak S/N ratio of $\sim$60. A 120 s exposure spectrum of the star $\nu$ Leo with V=5.26, d=55 pc and lying 2.5$\degr$ from IRC +10$\degr$ 216, was also obtained with the same instrumental setup, in order to provide information on foreground interstellar absorption and as a comparison spectrum for telluric lines.

Data reduction was performed using standard   IRAF procedures within the   ECHELLE package. After subtraction of the bias level, images were subsetted to avoid edge effects and flat-fielded using lamp flats taken at the beginning and end of each night. Spectra were then extracted using the   DOECSLIT task, allowing cosmic ray removal, inter-order background subtraction, optimal spectrum extraction and wavelength calibration using Thorium-Argon arc exposures which bracketed each stellar exposure. After heliocentric correction, the spectra were co-added using the   SCOMBINE task and output in   ASCII format to the   STARLINK package   DIPSO (Howarth et al. 1998) for subsequent analysis.

3.2 VLT/UVES observations

Following the failure to obtain a spectrum of Star 6 at the WHT, ESO time on VLT/UT2 (Kueyen) with the Ultraviolet and Visual Echelle Spectrograph (UVES), in service mode, was obtained. A total of 6 hours of integration time was achieved on Star 6 in a number of runs during December 2000 and January 2001. Using a 0.8$\arcsec$ slit width and both red and blue dichroics, spectra were obtained over six wavelength ranges: 3045-3870 Å, 3758-4980 Å, 4785-5761 Å, 5838-6811 Å, 6707-8523 Å and 8662-10430 Å, at a resolution R=50 000. Over a wide range of wavelength from $\sim$3758 Å to $\sim$8522 Å, continuum counts were sufficient to yield a signal-to-noise ratio approaching, and over certain ranges exceeding, 50. Data reduction was provided by the ESO/UVES reduction pipeline, based on the ESO   MIDAS package. Pipeline reduced, wavelength calibrated spectra were then corrected for the heliocentric velocity and converted into   ASCII format for output to   DIPSO for co-addition and analysis.