We present the latest results from the Mission Program NIRLT, the NIR spectroscopic observations of brown dwarfs using the IRC on board AKARI. The near-infrared spectra in the wavelength range between 2.5 and 5.0 μm is especially important to study the brown dwarf atmospheres because of the presence of non-blended bands of major molecules, including CH4 at 3.3 μm , CO2 at 4.2 μm , CO at 4.6 μm and H2O around 2.7 μm . Our observations were carried out in the grism-mode resulting in a spectral resolution of ~ 120. In total, 27 sources were observed and 18 good spectra were obtained. We investigate the behavior of three molecular absorption bands, CO, CH4 and CO2 , in brown dwarf spectra relative to their spectral types. We find that the CH4 band appears in the spectra of dwarfs later than L5 and CO band is seen in the spectra of all spectral types. CO2 is detected in the spectra of late-L and T type dwarfs.

ABSTRACT
1. INTRODUCTION
2. SPECTRA OF 18 AKARI OBJECTS
    2.1. CO Fundamental Absorption Band at 4.6 μm
    2.2. CH4 Fundamental Absorption Band at 3.3 μm
    2.3. CO2 Absorption Band at 4.2 μm
REFERENCES

• S. SORAHANA(Department of Astronomy, Graduate School of Science, The University of Tokyo, Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA))
• I. YAMAMURA(Department of Space Astronomy and Astrophysics, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA))