A SYSTEMATIC STUDY ON THE PROPERTIES OF DUST GRAINS AROUND M SUPERGIANT STARS

m supergiant stars are among the most luminous stars in the galaxy and are therefore of interest to study both the galactic structure and the evolution of our galaxy. most m supergiants lose their masses and dust formation takes place around them. since these stars emit much energy in the infrared via these dust grains, it is important to make clear the properties of these dust grains. infrared excesses of m supergiants has been characterized by the silicate dust emission and the freefree emission which is not seen around less massive cool evolved stars. however, recent mid infrared observations show that carbon dust features are also seen around several m supergiants together with silicate one, suggesting an occurrence of complicated nonequilibrium condensation. we propose here to take systematically infrared spectra of m supergiants using sws (sws01). our main objectives of this study are to make clear the properties of dust grains and to investigate the formation of dust grains around m supergiants. the obtained spectra are also useful to understand the atmospheric structure of these stars. furthermore, the results are used to estimate the mass loss rates and the chemical abundances of heavy elements and to give information on the mass loss phenomenon and its effect on stellar evolution. all these will give us useful data to investigate the galactic structure and the evolution of the galaxy. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]