| 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. |
