Infrared spectral observations of late-type stars

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The goal of the project is to examine the late stages of the stellar evolution by observing late-type stars and related astronomical objects in the infrared wavelength region. In this evolutional stages, late-type stars are believed to evolve through asymptotic giant branch stage to protoplanetary nebulae and then to planetary nebulae. In this process, mass loss from stars plays an important role. These stars, therefore, are covered with circumstellar dust envelopes(CDE)which are condenced from lost molecules. These stars are very bright in the infrared wavelength region due to the thermal omission from CDE.Late-type stars are generally classified into three types of stars(0-rich stars, S-type stars, and Carbon stars)depending on the stellar atmospheric composition. Since the composition and characteristics of dust grains in CDE of these three types of stars are different from one another, infrared spectral characteristics for these stars give important information for examining the evolution of three types of stars separately. We carried out both photometric and spectral observations for these stars and have got valuable information on the evolution of late-type stars.