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.