(Proposal ID) S15B-139

(PI) Ishihara, Daisuke

(Proposal Title)
Investigating non-steady processes in warm debris disks II

(Abstract)
The AKARI mid-IR all-sky survey detected mysterious debris disks which have 
large amount of warm circumstellar dust even at older (>1 Gyr) stages. These 
objects cannot be accounted for by the conventional theory on the evolution of 
debris disks. By the follow-up N-band spectroscopy of them using Subaru/COMICS 
etc., we have identified (sub-)micron sized grains which indicate recent 
transient events like violent collisions of grown-up planets, because smaller 
grains dissipate in a shorter (~1yr) time scale due to the radiation pressure 
of the central stars. They are important objects for understanding late stages 
of the planetary system formation. Recently, we have identified another ~30 
mysterious debris-disk candidates, by the intensive exploration based on the 
AKARI mid-IR PSC and the follow-up observations of the central stars. Among 
them, we propose the N-band follow-up observations of the objects, the disk 
fluxes of which differ between the AKARI 18 mu m and WISE 22 mu m measurements.
 This difference indicates the temporal variations of disk fluxes between 2006 
and 2010 or the existence of (sub-)micron sized grains showing spectral 
features in the mid-IR. Following our observations in the previous semester 
(S15A), we list up the other sub-smaple observable for this semester.