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4. Spectroscopic observations

A follow-up programme of spectroscopic observations of the C-rich star candidates has been initiated in order to confirm the chemical nature of stars observed in near IR photometry. Medium resolution spectra in the far red (tex2html_wrap_inline1025 Å) have been obtained for a subsample of 10 candidates, namely 03118+6144, 04256+5054, 04391+4904, 04469+3228, 05391+4757, 05581+2232, 05592+4627, 06175+2347, 07152+1228, 19580+2552, with the CARELEC spectrograph (OHP publication, 1986) attached to the 193 cm telescope of Observatoire de Haute Provence during 2 periods (November 28 to December 3, 1992 and November 20 to November 25, 1993). These spectra are displayed in Fig. 3.

This spectral range has been chosen because it allows to measure the reddest objects optically identified (tex2html_wrap_inline1027 brighter than tex2html_wrap_inline1029), and because many molecular features that characterize late giant stars (e.g., Turnshek et al. 1985) are located in this spectral range. The spectra of 9 objects definitely confirm that they correspond to bona fide C-rich stars, since all of them exhibit the CN bands that unambiguously characterize them. Among these objects, only 06175+2347 has a LRS spectrum (code 17), which clearly exhibits a SiC feature. As concerns the spectrum of 05581+2232, it shows TiO bands that characterize O-rich stars, but the near-IR photometric data might be inaccurate because of contamination by a nearby star.



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