THE NATURE OF OBJECTS WITH A 21-MU-M FEATURE

We report on the results of a search for an emission feature at 21 mu m from the IRAS data base. Using the sophisticated IRAS-GIPSY software , we are able to obtain and to select reliable LRS spectra from the IR AS data base. Twelve out of more than 900 sources from the IRAS Point Source Catalogue, whose flux at 12 mu m is larger than 5 Jy were selec ted as new candidates with a 21-mu m feature (5 objects are firmly ide ntified, 7 are on a ''waiting list''). These objects belong both to th e class of proto-planetary nebulae and to the class of young stellar o bjects. It is possible that the appropriate circumstellar environment for objects with a 21-mu m feature exists in two different stages of s tellar evolution which points to the basic nature of the physical and chemical processes involved.