THE MASS-LOSS HISTORY OF HIGH-LATITUDE SUPERGIANTS

A sample of 25 high latitude supergiants with spectral types B-G were surveyed in the (CO)-C-12 J=1-0 and J=2-1 lines using the Swedish ESO Submillimeter Telescope (SEST). Twenty percent of the sources were detected. For the analysis an additional 6 sources were added for which CO observations are reported in the literature. The majority of the detected sources have post-AGB mass loss rates and expansion velocities that confirm earlier suggestions that these stars, despite their supergiant-like spectra, are in fact low mass post-AGB stars (Trams et al. 1989). The non-detections and their systematic lower 60 mum fluxes can be explained assuming that they are low mass post-AGB stars, whose remnant AGB shells are significantly diluted and which are evolving rather slowly to higher temperatures.