<i>JHK</i>Magnitudes for L and T Dwarfs and Infrared Photometric Systems

Abstract

L and T dwarfs emit most of their radiation in the near infrared and their\nspectral energy distributions are dominated by strong molecular absorption\nbands. These highly structured energy distributions lead to JHK magnitudes that\nare extremely sensitive to the exact filter bandpass used. In the case of the T\ndwarfs, the differences between commonly used photometric systems can be as\nlarge as 0.4 mag at J and 0.5 mag at J-K. To address this problem, we have\nsynthesized J,H and K magnitudes for some of the common photometric systems and\npresent transformation equations. If the spectral type of the dwarf is known,\nour transformations allow data to be converted between systems to 0.01 mag,\nwhich is better than the typical measurement uncertainty. Transforming on the\nbasis of color alone is more difficult because of the degeneracy and intrinsic\nscatter in near-infrared colors of L and T dwarfs; in this case J magnitudes\ncan only be transformed to &lt; 0.05 mag and H and K to &lt; 0.02 mag.\n