(Proposal ID) S17A-153

(PI) Ishihara, Daisuke

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

(Abstract)
The AKARI mid-IR all-sky survey newly detected 53 debris disks (Ishihara et al.
2016). Some fluxes of the disks we found differ between the AKARI 18 mu m and 
WISE 22 mu m measurements. These debris disks suggested the silicate features 
caused by small grains <1 mu m. However, debris disks are considered to be gas 
free so that such small grains are blown out in a short timescale (~1 yr) by 
radiation pressure. Therefore, the silicate feature in debris disks indicates 
recent transient events such as the Moon-forming giant impact because smaller 
grains. On the other hand, these differences of disk fluxes at similar 
wavelength may come from 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. The confirmation of the existence of (sub-) micron 
sized grains in debris disks by the follow-up N-band spectroscopy of them 
using Subaru/COMICS may reveal the final stage of terrestrial planet formation.
In S17A, following the past semesters (S15A, S15B), we propose monitoring of 
the detected dust features as well as investigation of another 3 new targets.