COMPARATIVE-STUDY OF A [WC-6] NUCLEUS WITH OTHER EMISSION-LINES NUCLEI OF PLANETARY-NEBULAE

The central star (CSPN) of the planetary nebula M 1-25 (PN G 4.9+4.9) is classified as a [WC 6] star, the only CSPN of this subclass known a t this time. A comparison with the other emission-lines CSPN (the [WC] -class and the 'weak emission-lines stars' or wels-class) shows that ( 1) the characteristics of this [WC 6] star fit well inside the main pr operties of the other [WC] CSPN; (2) the [WC] CSPN seem to evolve from the [WC 8-11] (latter) to [WC 2-4] (earlier) subclasses, say from den se nebulae with cool stars to more extended nebulae with hot nuclei, a s for other CSPN; (3) on the two-colour IRAS diagram, the [WC] and the wels CSPN form two different groups: the progenitors of the [WC]-type CSPN seem to be carbon stars evolving along post-AGE tracks, whereas the wels CSPN seem to be related to OH/IR stars, some of them having p ossibly experienced a late helium-flash.