(Proposal ID) S17B-028

(PI) Ueta, Toshiya

(Proposal Title)
Direct PDI/ADl Imaging of the Circumstellar Dust Disk around Evolved Stars

(Abstract)
Stellar mass loss remains to be an important issue in astrophysics because the 
process itself has not been understood from the first principles of physics 
while the existence of nucleosynthesized elements in the Universe relies upon 
this process. Recent discovery of a Keplerian gas disk around post-AGB stars 
has added a new piece to this yet unresolved puzzle, because such a disk would 
undoubtedly play a role by modulating mass outflows. With this project using 
SCExAO/VAMPIRES plus HiCIAO in the hitch-hiker mode, we aim at (1) directly 
imaging and characterizing the sub-arcsec dust disk for the first time around 
target post-AGB stars for which the presence of a gas disk has been confirmed, 
strongly suggested, and expected based on the previous CO/dust interferometric 
and CO single-disk observations, and (2) searching for a circumstellar dust 
disk around descendants of post-AGB stars suspected to harbor a disk, via two-
band polarimetric/angular differential imaging. We will characterize the dust 
disk properties (the extent, geometry, mass, and scattering properties) in 
relation to the properties of the gas disk and on-going outflows, and possibly 
address the disk evolution while the circumstellar shell expands farther out 
as a full-fledged planetary nebulae.