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.

ABSTRACT
1. INTRODUCTION
2. OBSERVATION AND DATA ANALYSIS
    2.1. Sample
    2.2. Follow-up observations
    2.3. Detection of debris disks
3. RESULTS
4. DISCUSSION
5. SUMMARY
REFERENCES

• Nami Takeuchi(Department of Physics, Graduate School of Science, Nagoya University)
• Daisuke Ishihara(Department of Physics, Graduate School of Science, Nagoya University)
• Hidehiro Kaneda(Department of Physics, Graduate School of Science, Nagoya University)
• Shinki Oyabu(Department of Physics, Graduate School of Science, Nagoya University)
• Hiroshi Kobayashi(Department of Physics, Graduate School of Science, Nagoya University)
• Takahiro Nagayama(Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University)
• Takashi Onaka(Department of Astronomy, School of Science, University of Tokyo)
• Hideaki Fujiwara(Subaru Telescope, National Astronomical Observatory of Japan)