Astron. Astrophys. 353, 311-321 (2000)

2. Observational data

The SMC supergiant sample has been previously discussed by Lennon (1997) and below, we briefly summarize his target selection and observational setup; further details can be found in Lennon (1997).

A subset of the brightest B0-B9 supergiants in the SMC, taken from the compilation of Garmany et al. (1987), were selected. Particular emphasis was placed on the earlier spectral types in order to investigate the behaviour of the important CNO lines. Spectra were obtained at La Silla, Chile using the ESO NTT and the EMMI instrument operated by remote control from Garching in Germany. Data were acquired during two observing runs, on October 7th 1993 and October 22nd-24th 1994, using gratings #3 and #6 in the blue and red arms respectively. For both observing runs the ESO CCD#31 (Tektronix TK 1024 AB) was used in the blue arm, while during the second run the ESO CCD#36 (Tektronix TK 2048) was used in the red arm. Both CCDs have a pixel size of 24 µm which resulted in dispersions of approximately 0.45 Å per pixel in the blue and 0.32 Å per pixel in the red. For a 1" slit (used throughout) this gave FWHM resolutions of 1.18 Å, 1.27 Å and 1.21 Å at H, H and H respectively. Each star was observed in three wavelength regions; in one exposure the dichroic was used to simultaneously obtain data in the blue and red arms covering the approximate wavelength regions 3925-4375 Å and 6190-6830 Å, and another exposure in the blue arm covered the region 4300-4750 Å. Exposure times depended on conditions and the visual magnitude of the target but were typically 10 to 15 minutes giving a signal-to-noise ratio normally in excess of 70.

Table 1 contains the complete list of targets, ordered by their number in the stellar catalogue of Azzopardi & Vigneau (1982), their aliases in the catalogue of Sanduleak (1968), their photometric data (Azzopardi & Vigneau 1982, Garmany et al. 1987) and their spectral types, as estimated by Lennon (1997).

Table 1. Small Magellanic Cloud supergiants and associated data. Stellar identification numbers are from Azzopardi & Vigneau (1982; AV#) and Sanduleak (1968; Sk#). V-magnitudes and colours are taken from Azzopardi & Vigneau, except for those objects marked with a dagger, whose photometric data are taken from Garmany et al. (1987). The spectral types are from Lennon (1997) and AV 415 is a Luminous Blue Variable, whose spectral type from these data is somewhat uncertain. The luminosities were estimated as discussed in Sect. 5.2.

© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999
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