WARM MOLECULAR ENVELOPE OF M GIANTS AND MIRAS - A NEW MOLECULE FORMING REGION UNMASKED BY THE ISO-SWS

Our observations with the ISO SWS revealed that H2O band at 2.7 mu m a ppears as absorption already in an M2 giant beta Peg and strengthens t owards later M giants. Further, CO2 4.2 mu m band appears as absorptio n in an M7 giant SW Vir and especially strong in a Mira variable S Vir . The excitation temperatures of these molecular bands estimated from their band shapes turn out to be 750 - 1,250 K in M giants as well as in a Mira variable. Absorption features of CO and SiO at 4 mu m region appear to be weaker in cooler hi giants and almost disappear in S Vir (Mira), suggesting filling in by the emission of CO and SiO themselve s. The absorption and/or emission may be produced in a rather warm mol ecule forming region above the photosphere. This molecular envelope sh ould be related to the quasi-static molecular zone previously suggeste d from the high resolution FTS spectra of CO in the near IR.