| Abstract |
The process of dust condensation in the gas ejected from stars of variousspectral types during their evolution shall be an important issue to bedemonstrated observationally. While the intermediate- to low-mass starsare generally expected to play significant roles as the dust budgets inthe Milky Way and in the present universe, massive stars may contributeefficiently towards the chemical enrichment in the early universe byproviding heavy atoms synthesized during their stellar evolution andsupplying dust grains into the circumstellar space via the stellarmass-loss activities and the supernova explosions. However, we have quitea limited knowledge on the compositions and the amount of dust producedaround each type of stars, particularly, from the observational point ofview.We have carried out the multi-epoch mid-infrared observations ofperiodically dust-forming Wolf-Rayet binaries and dust forming novaetaking advantages of the high-spatial resolution capabilities achieved bymid-infrared instruments onboard 8m class ground-based telescopes, aimingto directly demonstrate the sites of dust nucleation in the stellarejecta. In this presentation, the sites of dust nucleation and thefollowing chemical evolution and/or destruction in the circumstellarenvironments are discussed based on those mid-infrared imaging andspectroscopic datasets collected so far. |
