New Observational Results of Of/WN - Transition Types

Abstract

Of/WN stars have been introduced by walborn (1977). These luminous stars are particularly characterized by the appearance of both the characteristic of emission lines of HeII and NIII and strong HeI and [NII] emissions. These objects have become particularly interesting due to the discovery of their link to the S Dor variables (Stahl et al. 1983, Stahl 1986, Wolf 1987). They are supposed to represent key objects in the evolution of massive stars being the immediate progenitors of WN stars. We observed the Of/WN transition type stars R127, R84, and S61 of the LMC with high dispersion spectroscopy in the optical and satellite-UV range. R127 is at present undergoing an S Dor-type outburst. In 1986 R127 became the visually brightest star of the LMC until it was surpassed by SN1987A in Feb. 1987. The spectrum in the optical range during the extraordinary bright outburst phase is distinguished by numerous P Cygni type lines of singly ionized metals. Since the beginning of the present outburst the spectral type has gradually become later and the equivalent spectral type as derived from our latest CASPE spectrum taken in 1986, August 22 was middle A. The IUE-spectrum of R127 during maximum is characterized by copious lines of singly ionized metals formed in the wind. A detailed disucssion of the optical and satellite UV high dispersion spectrograms of R127 taken during its present extraordinary bright outburst phase is forthcoming in Astronomy and Astrophysics (Wolf et al. 1987a).