NIR high-resolution imaging and radiative transfer modeling of the Frosty Leo nebula

We present a $K'$-band speckle image and $HK$-band polarimetric images of the proto-planetary nebula Frosty Leo obtained using the 6 m SAO telescope and the 8 m Subaru telescope, respectively. Our speckle image revealed clumpy structures in the hourglass-like bipolar nebula. The polarimetric data, for the first time, detected an elongated region with small polarizations and polarization vector alignment on the east side of the central star. We have performed radiative transfer calculations to model the dust shell of Frosty Leo. We found that micron-size grains in the equatorial dense region and small grains in the bipolar lobes are required to explain the total intensity images, the polarization images, and the spectral energy distribution.