Identification of Cool Iras Sources

The IRAS Point Source Catalogue contains a large number of very cool sources with color indices indicating temperatures between 200 and 350K. Among these objects one would expect to find late AGB objects (Mira variables, carbon stars, OH/IR stars) and also proto- and young planetary nebulae. Objects at the tip of the AGB and planetary nebulae would be expected to be non-variable; the others would be expected to vary.