We report results of $H$-band ($\lambda =$ 1.65$ \mu$m) imaging observations of young intermediate-mass stars using the Subaru 8.2-m Telescope with the adaptive optics AO36 and the infrared coronagraph CIAO. The targets consist of 16 Herbig Ae/Be stars (15 Herbig Ae stars and one Herbig Be star) and four additional main-sequence stars with infrared excesses. Five protoplanetary disks have been spatially resolved around the Herbig Ae stars with ages of 2–8 Myr. The resolved disks have outer radii of several 100 AU, and their surface brightnesses range from 10 mag arcsec$^{-2}$ to 18 mag arcsec$^{-2}$. The images reveal various morphologies in optically thick disks: spiral arms around AB Aur, a banana-split structure with an outer arm for HD 142527, a compact circumprimary disk of HD 150193, a faint discontinuous ring around HD 163296, and an unstructured face-on disk of HD 169142. The detection of an optically thick disk in scattered light implies that it is vertically flared, and intercepts stellar light at least in the outer region where those images were obtained. However, the surface brightness distribution, the resolved structure, and other observational characteristics suggest that the disks are unlikely to be continuously flared young disks with small grains well mixed with gas. The detection rate and the disk brightness do not correlate with the stellar age and the disk mass, but there is a tendency that the brightest disks are still surrounded by long-lived envelopes (AB Aur, HD 100546, HD 142527). The significant diversity of the disk structure can be attributed to the multiplicity and the initial condition of the local star-forming environments. The detections of companion candidates around our targeted stars are also reported.

We present high-resolution (0. ′′ 2) near-infrared images of the area surrounding the Herbig Be star LkHα 234 taken with the Coronagraphic Imager with Adaptive Optics (CIAO) and the adaptive optics on the Subaru Telescope. The near-infrared (J, H, K, L ′ and M ′ bands) images reveal circumstellar structures around LkHα 234 in detail. Eight young stellar object (YSO) candidates (Object B, C, D, E, F, G, NW1, and NW2) were detected at 2 ′′ -11 ′′ from LkHα 234. Objects B and C are likely variable stars, which is consistent with a young evolutionary status. Three objects (LkHα 234, NW1, and NW2) were identified in the 11.8 µm (SiC) and 17.65 µm images obtained with the Long Wavelength Spectrometer (LWS) on the Keck Telescope. NW1 and NW2 are thought to be embedded young stars. We suggest that NW1 and not LkHα 234 is the source illuminating the reflection nebula west of LkHα 234, although Object G may be another candidate. In our images, these objects are located at the center of the 2 µm polarization, and NW1 resides at the center of a monopolar cavity. The SED of NW1 suggests that it is a YSO with a spectral type of B6-7. Object F and G were discovered by our observations at 1. ′′ 9 and 2. ′′ 3, respectively, from LkHα 234, and their proximity to LkHα 234 suggests that they may be its lower-mass companions.

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The Compact Infrared Camera (CIRC) is a technology demonstration payload of the Small Demonstration-Satellite type-2 (SDS-2). The CIRC is an infrared camera equipped with an uncooled infrared array detector (microbolometer). The main mission of the CIRC is to demonstrate the technology of wildfire detection using a microbolometer. The CIRC is a small, lightweight, and low-cost thermal infrared imager for space applications. We employ athermal optics and shutter-less image correction to reduce the size, weight, and cost of the CIRC. In this paper, we show the details of the design of the CIRC.

The lateral density distribution of charged particles in EAS is one of the essential parameters for the analysis of individual EAS. To measure the lateral density distribution in detail, 100 ?i-m2 scintillators were arranged in a lattice configuration with a unit distance of 5 m or 2.5 m. The conventional EAS array of 20 scintillators was also used to obtain densities up to about 100 m from the center. These observations are much more accurate than those obtained previously, and it has been found that there are various types of structure functions which can be approximated by the functions for single cascades of age parameter from 0.6 to 1.6. It was difficult in some instances to fit the lateral distribution by a unique function, especially for small EAS.The two-dimensional map obtained by means of the above 100 detectors shows that individual EAS have rarely a conlplicated structure within a range of about 20 m from the axis. The results are discussed in relation to the character of high-energy interactions as well as to fluctuations in the development of EAS.