Debris disks are important observational clues to understanding on-going planetary system formation. They are usually identied by signicant mid-infrared excess on top of the photospheric emission of a central star on the basis of prediction from J-, H-, and Ks-band uxes and the stellar model spectra. For bright stars, 2MASS near-infrared uxes suffer large uncertainties due to the near-infrared camera satu- ration. Therefore we have performed follow-up observations with the IRSF 1.4 m near-infrared telescope located in South Africa to obtain accurate J-, H-, and Ks-band uxes of the central stars. Among 754 main-sequence stars which are detected in the AKARI 18 m band, we have performed photometry for 325 stars with IRSF. As a result, we have successfully improved the ux accuracy of the central stars from 9.2 % to 0.5 % on average. Using this dataset, we have detected 18 m excess emission from 57 stars in our samples with a 3 level. We nd that some of them have high ratios of the excess to the photospheric emission even around very old stars, which cannot be explained by the current planet-formation theories.

The activities of IRSF, a 1.4m infrared telescope operated under collaboration between Japan and South Africa, are presented brie y. The dedicated instrument, SIRIUS, which sits at the Cassegrain, has produced unique and prosperous science for 14 years. My talk involves; o concept of construction and operation, o publications and education, o the successive upgrading of the instrument, and o future plans.

InfraRed Survey Facility (IRSF) is our facility for near-infrared (NIR) observation located at South African Astronomical Observatory. The NIR camera SIRIUS on the 1.4m telescope provides three 7.7′×7.7′ images in the J ( 1.25μm), H (1.63μm), and KS (2.14μm ) bands simultaneously with a pixel scale of 0.45". IRSF has three unique capabilities, which are suitable for follow-up observations of AKARI-selected objects. Several synergistic studies with AKARI are in progress from stars to galaxies. We introduce advantages of the above unique capabilities of IRSF for further synergistic studies between AKARI and IRSF.

Using the AKARI mid-infrared all-sky survey catalogue, we are searching for debris disks which are important objects as an observational clue to on-going planetary system formation. Debris disk candidates are selected through a significant excess of the measured flux over the predicted flux for the stellar photospheric emission at 18 μm . The fluxes were originally estimated based on the near-infrared spectral energy distributions (SEDs) of central stars constructed from the 2MASS J-, H-, and Ks-band fluxes. However, we found that in many cases the 2MASS photometry has large errors due to saturation in the central part of a star image. Therefore we performed follow-up observations with the IRSF 1.4m near-infrared telescope in South Africa to obtain accurate fluxes in the J-, H-, and Ks-bands. As a result, we have succeeded in improving the SEDs of the central stars. This improvement of the SEDs allows us to make more reliable selection of the candidates.