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Infrared properties

Recent improvements in instrumentation now allows high quality infrared stellar spectroscopy. Despite only a tiny fraction of the luminosity of W-R and related stars being emitted in the infrared, this region contains extremely important wind diagnostic lines (e.g. HeI 2.058m) and allows studies of objects which are too heavily reddened to be observed at shorter wavelengths. For example, many emission line objects lying close to the Galactic Centre (Krabbe et al. 1991, 1995) show K-band spectra similar to WNL stars. In order to verify whether IR spectroscopic analyses are consistent with studies from optical observations Crowther & Smith (1996a) performed a detailed analysis of two WNE stars. Infrared profile fits to observations of HD191765 (WN6b) are shown in Fig. 2. Quantitative comparisons with previous optical and ultraviolet studies confirmed the reliability of IR analyses, as performed for several Galactic Centre stars by Krabbe et al. (1995). Crowther & Smith (1996a) also confirmed the presence of hydrogen in HD192163 (WN6b(h)), quite unprecedented for a hot WNE star (Table 1).

Paul Crowther
Mon Feb 12 13:51:35 GMT 1996