  We have updated our PHOENIX model atmospheres and theoretical spectra for
ultracool dwarfs with new opacity data for methane based on line strength
predictions with the STDS software. By extending the line list to rotational
levels of J=40 we can significantly improve the shape of the near-IR absorption
features of CH_4, and in addition find an enhanced blanketing effect, resulting
in up to 50% more flux emerging in the J band than seen in previous models,
which may thus contribute to the brightening in J and blue IR colors observed
in T dwarfs.
