SAO-244567 - A POST-AGB STAR WHICH HAS TURNED INTO A PLANETARY-NEBULA WITHIN THE LAST 40 YEARS

SAO 244567 (Hen 1357 = CPD -59(0)6926 = IRAS 17119-5926) is an IRAS source with far infrared colours and flux distribution similar to those of planetary nebulae. The IUE ultraviolet spectra obtained in July, 1988 and April 1992 show nebular emission fines and also the changes in the spectra suggest the formation of the planetary nebula and the rapid evolution of the central star. The optical spectrum of this star obtained by Henize around 1950 shows only the Halpha line in emission, while the most recent one, obtained in 1990 shows strong forbidden emission lines corresponding to a low excitation and young planetary nebula. The IUE ultraviolet spectra show evidence for the presence of stellar wind and mass loss. The stellar lines show P-Cygni type profiles and the terminal velocity of the stellar wind is approximately -3000 km s-1. The spectral type of the central star is approximately 08 V. The presence of a detached cold dust shell (125 K), high galactic latitude and abundances suggest that SAO 244567 has recently evolved from a low or intermediate mass progenitor star which has ejected its outer envelope during the AGB stage of evolution and is rapidly evolving towards hotter spectral types.