1 Introduction

Humphreys & Ney (1974) found near-infrared excess in HD 101584 and suggested that it is a massive F-supergiant with an M-type binary companion star (Humphreys 1976). However, HD 101584 (V = 7.01, F0 Iape (Hoffleit et al. 1983) was found to be an IRAS source (IRAS 11385-5517) (Parthasarathy & Pottasch 1986). On the basis of its far-infrared colors, flux distribution and detached cold circumstellar dust shell, Parthasarathy & Pottasch (1986) suggested that it is a low mass star in the post-Asymptotic Giant Branch (post-AGB) stage of evolution.

CO molecular emission lines at millimeter wavelengths were detected by Trams et al. (1990). The complex structure of the CO emission shows large Doppler velocities of 130 km s^-1 with respect to the central velocity of the feature indicating a very high outflow velocity. Te Lintel Hekkert et al. (1992) reported the discovery of OH 1667 MHz maser emission from the circumstellar envelope of HD 101584. The OH spectrum has a velocity range of 84 km s^-1 and shows two unusually broad emission features. Te Lintel Hekkert et al. (1992) found from the images obtained from the Australian Telescope, that the OH masers are located along the bipolar outflow. The post-AGB nature of HD 101584 is also suggested by the space velocity of the star derived from the central velocity of the CO and OH line emission. This velocity of $V_{\rm rad}=50.3$ $\pm$ 2.0 km s^-1 does not agree with the galactic rotation curve assuming it to be a luminous massive population I F supergiant.

Bakker et al. (1996a) studied the low and high resolution ultraviolet spectra and the high resolution optical spectra of HD 101584. Based on the strength of HeI (see also Morrison & Zimba 1989) N II, C II lines and Geneva photometry, Bakker et al. (1996a) suggest that HD 101584 is a B9 II star of $T_{\rm eff}=12000$ K $\pm$ 1000 K and log g=3.0. Bakker et al. (1996b) also found small amplitude light and velocity variations and suggested that HD 101584 is a binary with an orbital period of 218 days.

The optical spectrum of HD 101584 is very complex and shows many lines in emission. In this paper we report an analysis of the high resolution optical spectrum of HD 101584.