The central stars

Circumstellar molecules, brightness distributionsIRAM PdB data towardsIRC+10216(Guelin et al. 1996)Some molecules are ofphotospheric origin (e.g., SiS),some are photodissociationproducts (e.g., CN), andsome are due to circumstellarchemistry (e.g., HNC)For chemical reasons,these emissions shouldnot coincide (Guelin etal. 1993).