The enigmatic composite system HD 45166 - B8V +qWR or SdO ?

Abstract

High- and low-resolution IUE ultraviolet spectroscopic observations of the binary system HD 45166, previously classified as qWR + B8 V, obtained at several epochs are presented. The UV spectra show a photospheric absorption spectrum from highly ionized species like Fe v, which with the observation of B8 V absorptions in the visible, confirms the binary nature of the system. UV data obtained at different epochs show gross changes in the strengths of comparatively narrow emission lines in N IV, C III and He II. C IV 1550 shows a P-Cygni profile indicating a significant stellar wind from the hot object in the system, with v(infinity) of about 1200 km/s. An analysis of the UV and visible continuum, which shows no apparent epoch variations, yields the following parameters for the hot object: M(v) = -0.21, T(eff) = 60,000 K, log L/L(solar) = 3.84, R = 0.77 R(solar) and M = 0.5 M(solar). It is suggested that the hot stellar component may be an SdO rather than a qWR star. The cause of the observed variability in the emission lines remains an enigma.