DETECTION OF WATER ICE GRAINS ON THE SURFACE OF THE CIRCUMSTELLAR DISK AROUND HD 142527

Coronagraphic imaging for the Herbig Ae star, HD 142527, was performed using the Coronagraphic Imager with Adaptive Optics (CIAO) on the 8.2 m Subaru Telescope. The images were obtained in the H2O ice filter (λ = 3.08 μm) using adaptive optics (AO), and in the L' band without AO. Combining these data with previous observational results in the H and K bands, we derived the spectra of the scattered light from the circumstellar disk around HD 142527 and detected an H2O ice absorption feature in the spectra. This result can be explained by the presence of silicate and H2O ice grains of ~1 μm in size, according to the prediction model by Inoue et al. This grain size is consistent with previous observational study by Fukagawa et al. and Fujiwara et al. The present result demonstrates that high-resolution imaging of disk-scattered light in the ice band is useful for detecting H2O ice grain distributions in circumstellar disks.