Abstract
. Previous observations of M giants and supergiants have indicated that chromospheric Ca II,H and K emission is lacking in stars with high circumstellar dust-to-gas ratios (Hagen, Stencel, and Dickinson 1983, Ap. J., 274, 286). Observations with lUE detected other chromospheric lines (e.g., Mg II, Al II, Fe II) in stars without Ca II emission, indicating that the dust does not completely quench the . However, line intensities in dusty stars were reduced. (Carpenter, Stencel, and Hagen 1986, Ap. J., 308, 859). IRAS observations of visually bright M giants and supergiants and simple dust shell models indicate that the 60 and lO0 m excesses can be satisfactorily explained by silicate grains. Examination of individual IRAS scans indicates spatially extended emission for the stars R Dor,aOri, W Hya, a Sco, AH Sco, R Lyr, Cep, PZ Cas and L2 Pup at 60 m. Kay : STARS-CIRCUMSTELLAR SHELLS - STARS-CHROMOSPHERES
