The absence of circumstellar dust debris around G giants

摘要: The IRAS data base has been searched for evidence circumstellar dust around luminosity class III G giants, stars whose progenitors are mostly main-sequence A stars. While 20 percent of all dwarfs have which absorbs at least 5 x 10 to the -6th light from star, less than 3 giants such clouds. One possible explanation absence detectable debris is that Poynting-Robertson effect leads decay stars, and supply these grains not renewed indefinitely. In this case, derived upper limit grain radius about 0.2 cm bulk emitting far-infrared emission consistent with ground-based submillimeter observations. Another lack some original dwarf mainly composed relatively volatile material like water ice thermally evaporates in a short time during giant phase higher luminosity. 35 refs.