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Astron. Astrophys. 345, 233-243 (1999)

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2. Observation

Our program stars are summarized in Table 1. The sample consists of 26 J-type carbon stars, most of which were selected from the lists of carbon stars with the C-classification (Yamashita 1972, 1975), and those with comments on spectral peculiarities (Dean 1976). The IRAS database (NASA) and Stephenson (1973, 1989) are also important references. The silicate carbon stars were selected from the literature such as Willem & de Jong (1986), Little-Marenin (1986), Lloyd-Evans (1990), Lambert et al. (1990), and Chan (1993). Our sample includes five of them: EU And, BM Gem, V778 Cyg, NC 83, and GCCCS 447 1. We also emphasized such stars for which photometric data are available.


Table 1. Summary of the observations of 26 J-type carbon stars. The first row for each star is the exposure covering from 7800 to 7920 Å, while the second row is that covering from 7910 to 8030 Å

All the observations were carried out using the 74-inch reflector of Okayama Astrophysical Observatory (OAO 2), during the period between December 1987 and February 1993. The spectrum of each star consists of two adjacent exposures, covering from 7800 to 8030 Å. Each exposure covers 120 Å with an overlap of 10 Å allowed. The measured full widths at half maximum of thorium comparison lines appear to be about 0.4 Å, corresponding to a spectral resolution of about 20,000. The signal-to-noise ratios range from 20 to 800. For some of the program stars, large differences of signal-to-noise ratios are found between two exposures, because of the changes of the integration time and the weather condition. The descriptions of the spectrograph and the way of data reduction are found in Paper I.

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© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999