2. Observations and reductions
High-resolution spectroscopy of CS 22873-139 in the red portion of the spectrum (5000-8000 Å) was carried out with the ESO Multi-Mode Instrument (EMMI) at the 3.5-m New Technology Telescope (NTT), and in the blue ( Å) with the CASPEC spectrograph at the 3.6m telescope at ESO, La Silla. The spectral resolving power, as measured from the FWHM of lines in the Th-Ar comparison spectra, is about () for the EMMI spectra, and for the CASPEC spectra (). The FEROS instrument on the ESO 1.5m telescope was used to obtain lower spectra in order to provide additional (independent) information for the velocity zero point of this star, as our initial inspection of the EMMI data suggested the presence of a possible offset with respect to the values provided by Preston (1994) (see below).
The observing log is given in Table 1. All the spectra have been reduced with a semi-automatic code developed for échelle spectra at Paris-Meudon Observatory (Spite 1990). The code locates the spectral orders by optimal extraction and performs flat fielding and wavelength calibration from the comparison lamp spectrum with a minimum of user intervention. The ratios in Table 1 have been directly measured on the spectra. Preliminary results have been published (Nordström et al. 2000).
Table 1. Log of the observations
© European Southern Observatory (ESO) 2000
Online publication: August 23, 2000