To reveal the structures of a transition disk around a young stellar object in Lupus , ( catalog Sz 91 ) , we have performed aperture synthesis 345 GHz continuum and CO ( 3–2 ) observations with the Submillimeter Array ( \sim 1 \arcsec –3 \arcsec resolution ) , and high-resolution imaging of polarized intensity at the K _ { s } -band by using the HiCIAO instrument on the Subaru Telescope ( 0 \farcs 25 resolution ) .
Our observations successfully resolved the inner and outer radii of the dust disk to be 65 and 170 AU , respectively , which indicates that ( catalog Sz 91 ) is a transition disk source with one of the largest known inner holes .
The model fitting analysis of the spectral energy distribution reveals an H _ { 2 } mass of 2.4 \times 10 ^ { -3 } M _ { \sun } in the cold ( T < 30 K ) outer part at 65 < r < 170 AU by assuming a canonical gas-to-dust mass ratio of 100 , although a small amount ( > 3 \times 10 ^ { -9 } M _ { \sun } ) of hot ( T \sim 180 K ) dust possibly remains inside the inner hole of the disk .
The structure of the hot component could be interpreted as either an unresolved self-luminous companion body ( not directly detected in our observations ) or a narrow ring inside the inner hole .
Significant CO ( 3–2 ) emission with a velocity gradient along the major axis of the dust disk is concentrated on the ( catalog Sz 91 ) position , suggesting a rotating gas disk with a radius of 420 AU .
The ( catalog Sz 91 ) disk is possibly a rare disk in an evolutionary stage immediately after the formation of protoplanets because of the large inner hole and the lower disk mass than other transition disks studied thus far .