Spectroscopic Classification of Post-AGB Candidates: (Searching for Proto-Planetary Nebulae)

We have determined the spectral classification of approximately 50 candidates for post-AGB, proto-planetary nebula (PPN) objects. The candidates were chosen based on their infrared excesses as seen in the IRAS data. The spectra are of low-resolution (R~550) and were obtained with the Kitt Peak National Observatory 2.1-m and the Steward Observatory 2.3-m telescopes. Spectroscopy has permitted us to discriminate between PPNe and other objects with dust, such as pre-main sequence stars and planetary nebulae. Most of the objects appear to be PPNe, ranging in spectral type from K to B, with some of the hotter ones showing hydrogen emission lines. A number of the objects have published classifications, which we list for comparison. Some were previously classified as PPNe but a few are new identifications. We are also carrying on a photometric monitoring program of many of these objects to study light variability. This research is supported by the NSF (most recently AST-1413660)