| Description |
Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. However, there is a very small interesting group of stars in our neighbourhood (49 Ceti, and our discovery HD 21997), which may represent the missing link between these phases as indicated by the unexpected presence of debris-like dust content and measurable CO gas component. With the aim of discovering and characterizing more of these spectacular objects here we propose to obtain [O I] 63 micron observations of a sample of carefully selected young (<50Myr) debris disks of high fractional luminosity with Herschel-PACS. Our objectives are to 1) discover and determine the incidence of 49 Ceti-like gaseous debris disks; 2) characterize disk structure; 3) determine the timescale of gas dispersal; 4) perform a detailed investigation of HD 21997. New discoveries would lead to the definition of a new subclass of circumstellar disks, the gaseous debris disks. We required 17.2h of Herschel time for the observations. |
