A STUDY ON THE NATURE OF THE PECULIAR SUPERGIANT HD-101584

We present a study of low- and high-resolution ultraviolet, high-resol ution optical CAT/CES spectra and ultraviolet, optical and infrared ph otometry of the peculiar supergiant HD 101584. From the photometry we learn that the ultraviolet and optical energy distribution cannot be f itted in a consistent way and we need a model in which the UV and opti cal energy distribution are formed by different gas. The Geneva photom etry is best fitted to a B9II Kurucz model, T-eff = 12000 +/- 1000 K a nd log g = 3.0 +/- 1.0, with an extinction of E(B - V) = 0.49 +/- 0.05 . The observed spectral features in the spectrum of HD 101584 are clas sified in eight different categories based on the velocity, shape of p rofile and the identification. The high-excitation HeI (chi = 20.87 eV ), NII (chi = 18.40 eV), CII (chi = 14.39 eV) and NI (chi = 10.29 eV) optical absorption lines are formed in the photosphere of a late B-sta r (e.g. B8-9I-II). These absorption lines show radial velocity variati ons which are attributed to binary motion, with the secondary being a white dwarf or a low-mass main sequence object. The low-excitation P-C ygni lines in the optical and UV are formed in the wind. The number de nsity of absorption lines in the UV is so large that the wind spectrum acts as an iron curtain in front of the B-star, The terminal velocity of the wind of upsilon(infinity) = 100 +/- 30 km s(-1) is consistent with the star being a low-mass post-ACE star and the low effective gra vity is attributed to the presence of a nearby, unseen, secondary. We estimate a mass-loss rate of M approximate to 10(-8) M. yr(-1) Narrow absorption and emission lines are observed which are formed in a circu msystem disk with a typical radius of 10(2) R.