Nature of the peculiar supergiant HD 101584

From the photometry we learn that the ultraviolet and optical energy distribution cannot be fitted in a consistent way and we need a model in which the UV and optical energy distribution are formed by different gas. The Geneva photometry is best fitted to a B9II Kurucz model, T_eff_=12000+/-1000K and logg=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 classified in eight different categories based on the velocity, shape of profile and the identification. The high-excitation HeI ({chi}=20.87eV), NII ({chi}=18.40eV), CII ({chi}=14.39eV) and NI ({chi}=10.29eV) optical absorption lines are formed in the photosphere of a late B-star (e.g. B8-9I-II). These absorption lines show radial velocity variations which are attributed to binary motion, with the secondary being a white dwarf or a low-mass main sequence object.